Experimenting with waveguides using the LiteVNA

[joeqsmith]

Some time back I had read George C. Southworth's  Forty Years of Radio Research, published in 1962.   This book covers the history of waveguides.  I've often thought about experimenting with rectangular waveguides at home but the lack of a need and high costs of even used parts deterred me.   Outside of putting together a circular waveguide antenna from pork & bean cans, I haven't progressed.   

With the LiteVNA now having supporting a harmonic mode above 9GHz, I am once again thinking about it.   Many common sizes available far exceed the frequency range of the LiteVNA.   This company offers various surplus parts.
https://www.surplussales.com/index/RF-Waveguides.html

Link of waveguide dimensions.
https://www.everythingrf.com/tech-resources/waveguides-sizes

With ham bands providing  5.65–5.925 GHz, 10.0–10.5 GHz & 24.0–24.25 GHz, I tried some searches to see if anyone was playing around with it but didn't really find much out there.   

http://www.ham-radio.com/sbms/presentations/Walt_Clark/DROplexer.pdf

I'm curious if any members here are experimenting with them?

[Mechatrommer]

good luck digging the wormhole, we will follow where it suits... waveguide practicality only in tens of GHz domain and up, below that you can do in pcb (from what i read) but there is a DIY SA using sort of wave guide/chamber/tank at 1GHz region so you may want to look it up its Scotty's SA i think https://scottyspectrumanalyzer.us/ edit: yup it is cavity filter... https://scottyspectrumanalyzer.us/cavity.html

[rf-messkopf]

Tobias Plüss from Switzerland has built some pretty impressive waveguide devices, such as a bandpass filter, a directional coupler, and a termination. Also a cavity filter. For such projects you not only need the requisite test equipment, but also a well equipped machine shop, plus the required machining skills.

[joeqsmith]

http://www.w1ghz.org/QEX/Rectangular_Waveguide_to_Coax_Transition_Design.pdf

http://www.bobatkins.com/radio/10GHz_diode_detector_mixer.html

[coppercone2]

I saw that waveguide mixer on some old webpage to link a shed to a house with a 10GHz RF link IIRC

[joeqsmith]

Waveguide primer

https://www.microwaves101.com/encyclopedias/waveguide-primer#introduction

Contains lots of Rules of thumb

Very rarely does something in microwaves work as it was designed. Tuning waveguide structures requires some tricks. One such trick is to use a steel ball bearing inside the structure, that is moved around using a permanent magnet from outside the waveguide, while you monitor the part's performance using test equipment with signals applied. Once you find a spot that improves performance, mark it with an "X", then you can either drill and tap it and insert a tuning screw, or it's "hammer time" and you can use the concept of "dent tuning."

[coppercone2]

btw I had utterly horrible luck buying parts on ebay like adapters between waveguides the terminology is basically butchered to hell to the point that for small parts I really wanted to make castings out of silver

when you get to the gasketed parts its a total mess, buyer beware. I think relatively few people know the proper nomenclature of these things so you are going to have a serious struggle.IMO its worse then stuff related to pipes.

[joeqsmith]

I've been looking at photos of used parts.  Much of it seems like scrap metal.  I'm thinking small signal experiments with the VNA without any plans to gas fill. Flat flanges only. 

Looks like kirkby offers some waveguide cal kits.
https://www.kirkbymicrowave.co.uk/Support/FAQ/How-do-I-perform-waveguide-calibration/

[coppercone2]

yeah but alot of the good deals you can get is old airplane stuff from like cargo planes etc that have gaskets even if you don't need them so it will end up being tempting for alot of people. Or navy stuff that is also gasketed because of the ocean

[joeqsmith]

I saw what looked to be a cal standard last week.  No idea what size.  Seller had no information.  It was sitting at under $20 with three bids.    I just looked for it again but looks like it was sold.  

[coppercone2]

there is alot of weird educational things for waveguides for teaching RF physics (still used today). The idea was to teach the intro to electromagnetics class with demos. If you see very odd measurement aparatus it might be stuff meant to teach first principles of RF, not for industry+ use, e.g. the measurement is made in a round about way so the low order equations could be used to perform a lab (often very mechanical). Also hard to destroy and you might actually catch the person running with it since its heavy, the waveguide is used to teach reflection, I think I saw a catalog of those things some where (so the professor can do a sanity check with 'standards'). Easy to chain it down too. Back when the 141T was a hot commodity the students in the state schools/community colleges (when electronics vocational training was a thing) had some seriously strange apparatus (which could probobly be repaired/manufactured/supplemented by the university machine shop without needing IC etc). Kill two birds with one stone (advanced physics and advanced machining students make the stuff).

I know there are very real serious waveguide related apparatus, but there is also the low accuracy learning stuff, I am almost sure I saw a big catalog full of it where it was marketed as such for much lower prices... and like technican grade stuff for getting things 'in order' before the wizards showed up to get it tuned just right, like during airport construction etc... just so the fitters don't get it totally wrong.

Waveguide VNA calibration is interesting, that is getting into TRL type stuff, state university will not give you that.

[TWMIV]

I did my Masters work in synthetic aperture radar using waveguides. There are a lot of interesting things you can do with them. We did microwave NDT and materials analysis, almost entirely with waveguides as they make great antennas in the nearfield.

Have an object of unknown dielectric properties that can fill the aperture of the waveguide? You can inverse the properties of that material out. See doi:10.1109/19.816128 for the basis of the technique. 
You can also extract the permittivity of some planar materials though a SAR scan, but I have not had much luck extracting the loss factor using SAR. I believe the phase difference between measurements was causing issues getting the loss factor, and I had to finish my thesis on a different topic before I explored that any further.

[joeqsmith]

It appeared to have been a few stepped shorts.  No slit and I assumed EDM.   Not sure what else it would have been used for beside calibration.

I would say the educational level is several steps up over where I am with my bean cans.  I had put an offer down on this kit some time ago but no bites.  No real goals in mind outside of playing around.    

https://www.ebay.com/itm/143596987580?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20180816085401%26meid%3D2cc6f70776bd4fb2a9cbd4e222bf8e46%26pid%3D100970%26rk%3D1%26rkt%3D1%26sd%3D143596987580%26itm%3D143596987580%26pmt%3D0%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100970.m5481&_trkparms=pageci%3Ae8ec71f6-75ba-11ed-8daf-42aeea92eaef%7Cparentrq%3Ae9b2b9041840a768e9b39eeeffffefc2%7Ciid%3A1 

[coppercone2]

thats nice for a physics lab class thats not garbage

I wonder what that ends up looking like when you get broke ass waveguides instead of a broken breadboard and out of spec transistors with a power supply that is stuck at 6.2V for a microwave class. All the bolts are cross threaded so use these pencils and paper clamps, please take the folded gum wrapper that the TA found in the trash to seal the waveguide structural cracks after the janitor reamed the waveguide that kids were playing stick ball with with a chair leg (9:30 pm friday physics final 30% grade lab)

[TWMIV]

If you just want to get started what you need at a minimum would be a coax adapter, a short (flat plate), a spacer, and a load.

That would let you make calibrated reflection measurements. Add a through section to help kill off any evanescent modes and with a decent vna your in business. With a second coax adapter you can do trl cals in addition to ssol and can play around with cross polarization or transmission stuff.

Horn antennas, and even more complicated structures can be effectively 3d printed and coated in conductive paint at and below x-band. Surface finish becomes more important with increased frequency as you would expect.

We were mounting a tv to use as a monitor in a lab one day and needed to find the studs. Threw an x-band waveguide on a Field-fox (keysight portable vna) and just rubbed it along the wall to find the largest s11 return. That might actually be a fun project to build up from scratch...

[joeqsmith]

Getting started, I wonder if the VNA would even need calibration.     I'm thinking just a couple of transitions to start with.  Saw a matched set yesterday that may be a good fit.

The WR90 is fairly common but I wonder how stable it even is.   Cal the VNA at the ends of the cables with SOLT,  bolt the two transitions back to back and insert them in the path.  Would we expect S21 to be < +/-1dB over the range of the NanoVNA?   

The cutoff of the lowest order mode for WR90 is above  what the Nano can produce without harmonics.  At least with mine, once you get above 8G, it gets pretty bad.  At 9 after cal, S21 is maybe +/-5dB?  Even when using the leakage term, the floor is maybe 15dB down is all at the highest frequencies.   So there's a pretty limited range that it may be able to be used.   I did buy an old PNA and am working on increasing it's frequency range but still, it's limited to 9G.  It's certainly much more stable and lower noise than the Nano though.   

If the WR90 components are typically stable down to their cutoff,  it may be fine.  From what I have been reading, I suspect that some parts may have a very narrow range it can be used and it may be well outside the range of the Nano.  With many parts being old surplus, finding data sheets seems to be rare.   

***
I have attached some data I recently collected that compares the low cost VNA with my used Agilent.  One is looking at a high pass.  The other looking at the floor.

[joeqsmith]

All the bolts are cross threaded so use these pencils and paper clamps

Watched a few videos where they use the paper clamps to hold the parts.  I guess in a lab environment your not expecting a lot of movement and get away with it.  I couldn't find it but here is one where they use some wood clamps:

https://youtu.be/l_hlrQDcJAo?t=152

[coppercone2]

Lol. It might actually be a good project to make special spring clips to hold the waveguide pieces together. Clico clips also come to mind. Good project for wire that’s not make another diy hose clamp. You just need to be sure it does not scratch.

[TWMIV]

Strong clamps work well if everything is aligned. Well fitting shoulder bolts and some clamps will get you most of the way there if it is a temporary setup that isn't going to move.

I used shoulder bolts for anything that didn't have gauge pin holes for alignment.

[joeqsmith]

For everyone's amusement, I attempted to create the worlds worse WR90 waveguide with back-to-back transitions using some FR4.   The seam is in the worse possible location and it's held together with O-rings.  The dimensions are not precise.  There was ZERO attempt to tune it.  I'm not sure what would make it worse.

https://www.rfcafe.com/references/electrical/waveguide-chart.htm

I ran a SOLT cal on the LiteVNA and measured S21 with the cover off, then with it on sweeping from 100k to 9.3G.  It appears to have a 3dB cutoff around 6.9G and remains somewhat flat up to the limit of the VNA (again, the VNA is VERY poor in this region.) 

[joeqsmith]

Running a SOLT from 7 to 9GHz then looking at S21.   It hard to believe any used production made transitions would be this poor.    Gives me some sanity check.  Then again, the Lite certainly wasn't designed for this.  Too bad that PNA is limited to 9GHz.  I wonder where it starts to fall off on the high side. 

[joeqsmith]

My first waveguide experiment.  Took out my hacksaw and proceeded to chop my new WR90 waveguide in half.  The humanity of it all!!  Well, not half.  The base slipped in the vise and it's anything but square.  So much for precision machining....

Two new transitions were placed onto some high tech mounts.   I then measured S21 with a wire polarizer with the wires vertically and horizontally mounted.  Up till about 8GHz, there's a nice 10dB drop.    Like my homemade polarizer? 

[0culus]

Interesting experiments!

I have a growing collection of waveguide components, mostly WR-90 with some WR-62 thrown in for good measure. My most recent "build" is a simple doppler radar using surplus Raytheon circulator and a Scientific Atlanta WR-90 crystal mixer with adjustable stub. The microwave source can be either my 8672A fed through a TWT amplifier to get a little less than 2 watts, or a X band gunnplexer. It's quite sensitive. I've been using my Tektronix 547 with a Type 1A7A high gain diff amp to view the IF of the xtal mixer. That allows me to cancel out 60 Hz noise and use very small volts/div settings.

I always am on the lookout for deals, plus I've gotten some hand me downs from elmers (that circulator mentioned above was a particularly good one to get as a hand me down!) Coaxial transitions, especially for WR-90, are stupidly expensive. I only have one. I have three WR-62 transitions as well as a few for proprietary Litton ribbed waveguide that is similar in size to WR-90 but has a lower cut-off.

[Mechatrommer]

The bare shorting wire in ceramics filled fuse tech that is in waveguide tech i suggest to get a pro/free em solver sw to back it before wasting wr90 materials.. why dont build for lower freq where litevna is most sensitive? Even if you can make a successful tunnel at 9GHz, the other components will be eye watering expensive, ymmv.

[joeqsmith]

The bare shorting wire in ceramics filled fuse tech that is in waveguide tech i suggest to get a pro/free em solver sw to back it before wasting wr90 materials..

While jumping a fuse because we never learn how not to pop them in the first place is one work around, certainly starting out with some scrap materials to run some simple experiments does reduce the costs.   

I did play a bit with some free simulators a while back in response to someone's question on layouts.   The free simulators are very limited and I spent more time trying to work around those limitations than reaching my goal.   So for now, solder and PCB materials are my tools of choice for trying out the basic concepts.  No doubt this will become a limiting factor later on but fine for the basics.       

why dont build for lower freq where litevna is most sensitive? Even if you can make a successful tunnel at 9GHz, the other components will be eye watering expensive, ymmv.

I guess I wasn't clear on that.   I don't see a problem showing the limitations of the LiteVNA.  At $120, I don't think too many people are expecting a lot out of it.  The developers included harmonics to extend the frequency range so customers could play with it.  That's what I intend to do.   WR90 is fairly common in the used/surplus market and falls into that extended range. 

In this video the teacher is running a similar experiment on polarisation.  Beyond talking about the experiment itself, he is also covering  the tools, their age, their costs...   Personally I would get more out of a class using the low cost VNA and some basic materials where I work the math and build the structures, than watching a teacher perform them with purchased parts.   

[Mechatrommer]

The developers included harmonics to extend the frequency range so customers could play with it.

have you seen how crappy is the harmonic mode (6-9?GHz) when doing just a simple SOL calibration? iirc its very crappy.

[rf-messkopf]

I did play a bit with some free simulators a while back in response to someone's question on layouts.   The free simulators are very limited and I spent more time trying to work around those limitations than reaching my goal.   So for now, solder and PCB materials are my tools of choice for trying out the basic concepts.  No doubt this will become a limiting factor later on but fine for the basics.       

There is openEMS, which is a 3D FDTD EM solver, which is perfectly capable of simulating waveguide structures. It does not have a a GUI interface though. So you will need an external CAD program to draw conductor structures, and use a third party tool for 3D result visualization, e.g. Paraview. Meshing and the simulation itself is controlled by an Octave script.

As an example, here is a video on an openEMS simulation of a waveguide magic tee, which demonstrates field visualization and the extraction of S-parameters:
.

There was a very interesting talk by Thorsten Liebig, the openEMS developer, at FODSEM 2019:
.

The openEMS website hosted at the University of Duisburg-Essen is currently down because there has been a large-scale hacking attack on the university's systems, see here for some news coverage if you read German.

[joeqsmith]

have you seen how crappy is the harmonic mode (6-9?GHz) when doing just a simple SOL calibration? iirc its very crappy.

Sure and I have posted data for it.  This thread is already extremely large and I imagine overwhelming so I have included a link to save you some time searching for it.       Good enough for that first simple experiment. 

[joeqsmith]

There is openEMS, ...

It's been a few years since I looked for free software.   I assume you have used it and will have a look.   Which tools did you use with it?

[joeqsmith]

After damaging the covers with the hacksaw, I made two new ones and soldered them in place rather than using the O-rings.   I then squared off the edges.  Next I ran a 2D swept of one part.   

[joeqsmith]

I made up a horn for the second part using PCB material. 

[joeqsmith]

I epoxied the horn to the transition and then soldered the whole mess together.    It's not pretty, so I added some primer to give it that professional look.   A setup like this from Pasternak would cost over $1000.   Here's the real deal: 

https://www.pasternack.com/wr-90-waveguide-standard-gain-horn-antenna-20-dbi-sma-pewan090-20sm-p.aspx

The horn was mounted to the stage and swept.   I actually ran the two antennas back-to-back within minutes of each other.   I stored the transition without the horn to memory and overlaid them to provide an easy comparison of the effects.   

[joeqsmith]

Adding a horn to the second transition. 

[rf-messkopf]

It's been a few years since I looked for free software.   I assume you have used it and will have a look.   Which tools did you use with it?

So far I've been using openEMS only through QucsStudio, which automatically generates the 3D model and simulation script, and runs it. However, this limits you to microstrip structures, i.e., planar copper over a solid ground plane. But it has the benefit that the EM simulation is integrated in a circuit simulator, so you can add lumped elements and other structures very easily. I've been using it to tweak microstrip filters, bias tees and couplers, which works very well. Up to now this has been covering all my needs.

To simulate waveguide structures and devices, or antennas, with openEMS you would need a 3D cad like FreeCAD, and Octave to write and run the simulation scripts. If you only want frequency domain data like S-parameters, you could use Octave's own plotting functions, or dump the S-parameter data to a file, e.g. in Touchstone format, by setting up a script to do that. If you want animated field visualizations it is my understanding that you need something like ParaView, as has been shown in the videos.

Some time ago I've been looking at openEMS's documentation and examples. It is my impression that if you know some Matlab/Octave, the scripting part is not rocket science. You have to gain some understanding of FDTD simulations though, in order to set up things like the mesh and the excitation (frequency range, decay energy, etc.), as well as material properties, to get reliable results in finite time. But that is already the case for microstrip with QucsStudio, even though there are far less degrees of freedom.

If I were to venture into this area, I would have to learn some 3D CAD first. To get started with openEMS it would probably be a a good idea to get some of the examples on the homepage working and then tweak them. Too bad it is down at the moment, there is only the Github stuff available. But there is certainly a steep learning curve involved, as with many things related to electronics, and there is never enough time in life (I'm currently trying to get my head wrapped around Verilog and Lattice FPGAs). 

[coppercone2]

Thats a nice horn. I wonder if you can lay a wire in the seam to make that joint stronger.

I will tell you though that using PCB material is not a bad idea because if you try this with thin copper sheet, which you can form nicely, it becomes very fragile, and you would need to like put fiberglass on it or something to make it any bit decent.

For working the copper, if you are reusing it, you can throw it on a BBQ for a while then dunk it in water (clean it up), then use a rolling pin to flatten it out very nicely.

And I have experimented with using pen electroplating of solder joints like that and it works like crap.

[coppercone2]

Also if you make your own FR4 PCB, I think you you can do this to get perfect right angles inside

1) make a FR4 segment of the correct shape for a horn side.
2) when you glue the copper to the FR4, make it bigger then it needs to be, so free copper hangs off the edge.
3) Put it together so there is a full copper seam on the inside and the outside looks like a pirogi/dumpling
4) flood the inside with solder
5) use a long square edge file to cut a square on the inside


It will be mechanically correct then

[joeqsmith]

I have played with both FreeCAD, and Octave some.  I tried to use FreeCAD to create a model for some free FEA software.  They showed a lot of very nice drawings with it but I soon realized these were drawn with a professional CAD package and then imported into FreeCAD.  It turned into a big waste of time.   That's been at least 10 years since I last looked at it and I am sure it has improved.

My last time playing with Octave, I wanted to work on some large data sets and set out to build it for 64-bits.   I dare say that was a few weeks effort trying to locate everything needed to rebuild it.   In the end, I did get it working but there were a lot of bugs.   I used that same version I think with your scripts.   Again, guessing they have moved beyond the 32-bit world by now and have most of the problems solved.

Watched the first video.  He never shows the 20 weeks of effort that went into getting to that point.      He could have made a 10 part series on this one component, walking you through all of the painful steps.   I would watch it!

A few of us were recently posting about the Lattice tools and licensing.   I've used their very old PAL software and their newer software for small CPLDs.  I don't remember having any problems with it.

[joeqsmith]

Thats a nice horn. I wonder if you can lay a wire in the seam to make that joint stronger.

I will tell you though that using PCB material is not a bad idea because if you try this with thin copper sheet, which you can form nicely, it becomes very fragile, and you would need to like put fiberglass on it or something to make it any bit decent.

Wire could possibly improve the strength.  I could also fibreglass the entire structure which would really improve its strength.   Adding a cover to the front would also help.    Triangles are good!   Double sided would have also helped as we could tack both sides. 

For working the copper, if you are reusing it, you can throw it on a BBQ for a while then dunk it in water (clean it up), then use a rolling pin to flatten it out very nicely.

The copper sheet I show is very thin and I will typically grab what ever I have on the desk in front of me to flatten it out.   

Also if you make your own FR4 PCB, I think you you can do this to get perfect right angles inside
...

For angles, I just block up the parts and solder them.   I typically tack solder the parts at first and then run my beads once things are together.   In this case I'm not too concerned.   All I am doing now is just a toe dip to test the waters....   Eventually when I start working with WR90 I will have some idea what the performance should be.  I doubt we could buy a production horn and transition as poor as what I have shown. 

I think we could make for example a slotted line with everything (2 transitions, slotted waveguide)  in one part without too much trouble but at some point, it would be much nicer to have a set of building blocks to mix and match.   

[coppercone2]

for soldering FR4 together I remember there is a document somewhere that describes the construction of the chassis for radios and he recommends that you actually do not use a right angle but like a 91 degree angle because it contracts when it cools down. That can improve quality of those things also, to have angle offset blocks around for rapid prototyping with PCB

[joeqsmith]

Interesting.  I've always just used 90 deg blocks and called it good.    I have used it to make cases for some of my projects where I want something fast and am not concerned about the looks of it.  For example, opening video shows a couple of cheap RF detector boards built into a PCB case for a simple Watt meter:

https://youtu.be/JHsgbu7brYI

From the following site

In most radars, the feed horn is covered with a window of polystyrene fiberglass to prevent moisture and dirt from entering the open end of the waveguide.

 
https://www.radartutorial.eu/03.linetheory/Horn.en.html

I could certainly add a sheet of PCB to one of the horns and compare results.   I like their 3D plot.  I noticed that my software doesn't calculate anything when running 2D mode.  Just an oversight.   

***
double negative.

I found a sheet of fibreglass that is just about the right size for the horn.   I'll glue it up. 

[joeqsmith]

Two horns with fancy paint.   Plots showing effect of adding the cover.   There may be some difference masked by the Lite's noise. 

[joeqsmith]

Previous test was two horns pointed at one another then inserting the sheet of fibreglass between them.   I glued on the cover to the second horn.   I then swept both horns.  Blue trace is horn with no cover.  Patterns are sightly different due to errors in construction.   

Next I ran a 3D sweep on the horn without the cover.

[joeqsmith]

https://www.electronics-notes.com/articles/antennas-propagation/rf-feeders-transmission-lines/waveguide-junctions.php

To look at the operation of the Magic T waveguide junction, take the example of when a signal is applied into the "E plane" arm. It will divide into two out of phase components as it passes into the leg consisting of the "a" and "b" arms. However no signal will enter the "EH plane" arm as a result of the fact that a zero potential exists there - this occurs because of the conditions needed to create the signals in the "a" and "b" arms. In this way, when a signal is applied to the H plane arm, no signal appears at the "E plane" arm and the two signals appearing at the "a" and "b" arms are 180° out of in phase with each other.

***
This site appears to have it correct:
https://www.everythingrf.com/community/what-is-a-magic-tee

[joeqsmith]

MagicT_InpE_Out1_2:  LiteVNA's Port1 attached to the magic-T's E-Plane.  H-Plane port is terminated.   Port2 is then connected to each of T's co-linear ports.  We can see the 180deg phase shift as expected. 

MagicT_InpH_Out1_2: LiteVNA's Port1 attached to the magic-T's H-Plane.  E-Plane port is terminated.  Port2 is then connected to each of T's co-linear ports.  We can see the phase remains constant.   

https://www.microwaves101.com/encyclopedias/magic-tees

[joeqsmith]

MagicT_InpCoLin_OutH_E_CoLin:  LiteVNA's Port1 attached to one of the magic-T's  co-linear ports.  Port2 is then connected to the H-plane (yellow), the E-plane (violet) and finally the second co-linear port(red).   

There's more leakage than I would expect but no surprises.   Keep in mind LiteVNAs poor performance in this range and no attempt was made to calibrate the system.

MagicT_InpH_OutE:  LiteVNA's Port1 attached to the magic-T's H-plane.  Port2 is then connected to the E-plane.   Unused ports are terminated. 

[joeqsmith]

Another good ham link.   
http://www.w1ghz.org/waveguide/Waveguide.htm

[joeqsmith]

I want to attempt to construct a waveguide with some hobby brass next.   The plan is to again include the transitions.  It's a lot of thermal mass and I am thinking maybe silver solder.   

[coppercone2]

welcome to distortion land if you try to braze corner joints

If you don't bend a corner piece for a lap joint you will have a ugly time IMO when its getting red hot

but I never tried with thin brass. It might work. The amount of fixturing people use for like stable work is kinda ugly (never got that far, its just tooo mucch). Also ventilate well because thats alot of brass surface area to be heating, it might fume.

[joeqsmith]

I would use a jewelers torch head.  If you saw that home made current shunt I constructed for the UT61E DMM, this is how I silver soldered the brass contacts to the shunt.   Those were very small parts compared to this.

The brass I am using is 1mm thick from K&S (see link).  You can find much cheaper sources than the one I linked.   I cut off a section and tried to bend and solder to it.  Even with a small iron, it wasn't a problem to get it hot enough to flow.  So maybe I can get away with using my larger iron. It bends fairly easy and is soft enough that there are no signs of any cracks.    Thinking two L's rather than a U channel.

https://www.ebay.com/itm/225111789751

[joeqsmith]

I have not bent the ends or solder anything except the connectors.  The radius is about as tight as I dare make it.   I laid some material to close off the ends and held it together with my hand.    Yellow trace is with the waveguide apart, Violet with it together and Red with a thru applied.   The waveguide has a bit of loss but hopeful this will improve once I actually assemble it.   

[joeqsmith]

Bent up the two ends and tacked (solder) it together.  I used some foil tape to seal it for now.  Yellow showing S21 with calibration, Red with an open.   Time to drill some more holes.

[coppercone2]

you can cut a v groove into it and bend it and then seal that with solder to get a right angle without the bending radius but you need a 90 degree endmill, I see click spring do that, but he uses fairly thick brass

[joeqsmith]

With it being a mm thick it may prove difficult to cut such a V.  I did try bending it tighter and eventually used a peen hammer.  Still no signs of cracking.  Compared with the PCB and fillet, I'm not sure we are any worse off.   

Interesting paper "Mismatch Caused by Waveguide Tolerances, Corner Radii, and Flange Misalignment"
https://library.nrao.edu/public/memos/edtn/EDTN_215.pdf

I tried to find Brady's paper he references from 1969 but no luck yet. 

Finished up the assembly and had to resort to propane  to preheat the brass to solder the seams.   No problem really. 

[coppercone2]

For milling thin material I think I would take a thick slab of metal and cut a slot in it that the cutter can fit through then clamp it down tight over the brass sheet so its held down very well and mill with a vacuum. It might work with a router

You need to level everything etc, probobly pain in the ass.

[joeqsmith]

May be a pain in the ass but for me the question is would it be worth it?

It would be interesting to compare a set of high quality transitions and waveguide with what I have shown to get some idea how much it would improve things.   Do you have any feel for this?   Do you own a Lite VNA and have some good WR90 bits that you could try and measure?  If you have a VNA better than the Lite and could run them on that, that would also be very helpful as a comparison.   

I've shown the noise floor of the Lite compared with my old Agilent.    If I run an SOLT with my LiteVNA torquing each connection, then attach three different thru adapters you can see the error band is pretty wide as we move beyond 8GHz. 

[joeqsmith]

Made some progress with it today.

[coppercone2]

I might have a section of brass WR90 I don't know what dimension it is. The one I screwed up trying to electropolish.

 I would need the coaxial adapter though.

I think I read some numbers somewhere that its 1-5% difference with the corner stuff, or maybe it was a book. I think the more rounder it is, the more propagation you get in the circular waveguide mode, which I think is more broad band, so you get like a less band pass feature from the wave guide.

[joeqsmith]

Would be great to have a sanity check.  Here's another paper that talks about the effects of the corner radii. 

https://iopscience.iop.org/article/10.1088/1681-7575/abd371

I look from time to time for used bits.  For $130 you can own this nice transition to use for your own testing.  Surprised to see the damage to the inside.   

https://www.ebay.com/itm/294867475982?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20180816085401%26meid%3De581e7ae342548db84848ee010d10aa7%26pid%3D100970%26rk%3D1%26rkt%3D10%26sd%3D294867475982%26itm%3D294867475982%26pmt%3D0%26noa%3D1%26pg%3D2380057%26brand%3DUnbranded&_trksid=p2380057.c100970.m5481&_trkparms=pageci%3Ae044fd31-7e59-11ed-b983-dafb5026ee95%7Cparentrq%3A22324c151850aa7105adb607fffebce2%7Ciid%3A1

[joeqsmith]

Here's another paper that discusses the corner radii.  Fig. 4 showing effects of radius vs return loss.  Mine is bent with 1-2mm inside. 

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016RS006027

[joeqsmith]

Note these production bits have an even more dramatic radius.   

Nice free haul.  Would like to have that adjustable short. 

[coppercone2]

dear lord, maybe for 35$

that is the wave guide that was being dragged behind plane it fell off of when it got stuck in a cargo net that ripped. You gotta de-rate the damaged hardware you know?? I love how there is a much nicer condition one for the same price

edit: remembered end launchers never had favorable prices

I don't have money to get into wave guide right now. I got too much other stuff. I need to unfuck the microwave equipment too like replace fans etc so I can stand being around it.

[coppercone2]

I don't think I will have a happy chirstmas and new year if I do this now. Maybe q1 2023

I was feeling great about it Q2 2022 but then I repaired too many things and i still don't want to look at the VNA etc.


when you get too heavy into broken HP

[joeqsmith]

If that were in my stash, I would gladly sell it to you for $35 and include free shipping.   No returns.   

[joeqsmith]

Here is my $20 worth of hobby brass and two decent SMA connectors running on both my old Agilent and the LiteVNA (both calibrated).   Note the Lite's frequency shift and dip in the passband.  Still for a $120 VNA that fits in your shirt pocket,  the fact it can show anything remotely close to the PNA impresses me.   I'm easily amused. 

With Dislord's latest changes to the Lite's firmware, I no longer have to be careful about the setup.  It just works as expected.   

[joeqsmith]

This is my friend Shrimpshowromma's LiteVNA that I have abused.  There are no TVSs on the front end.  The IF gain has been bumped.  Bypass has changed along with some other values. 

I used the included cables and cal standards supplied.  Note that I have modified the included short and open to add an end cap to allow me to use a wrench with both.  I used the load that I sorted (same part I used to cal the other Lite).   

Looking at S21 with a thru, the error window is improved and when looking at the filter, we no longer see the droop in the passband.  This VNA originally had higher noise than mine.  I'm surprised that it's still as good as it is. 

[joeqsmith]

Shown is a PCB version of the filter next to the hobby brass one.  Note the distance from coax transition to post on the PCB is no where near what is called for.   Oddly there is little difference between the two filters. 

The Lite was set to 1kHz IF.  I set the PNA to 1k and 150Hz to show the difference.   Both VNA's were then caled for 7.8 to 8.6G to zoom into the filter. 

[joeqsmith]

Looking at the LiteVNA groups.io,  there is a thread where people were experimenting to 15GHz before limiting it to 9.3G.    Shown is my last attempt of a making a bandpass filter.   No tuning this time.   

https://groups.io/g/liteVNA/topic/first_tests_above_6_3ghz/87993520?p=Created%2C%2C%2C20%2C2%2C20%2C0%3A%3Arecentpostdate%2Fsticky%2C%2C%2C20%2C2%2C20%2C87993520%2Cprevid%252525252525253D1643508180797191034%2Cnextid%252525252525253D1640273623127907015&next=1

[joeqsmith]

Of course to test that last waveguide filter with the Lite requires solving a few problems.  Even if Dislord were to extend the harmonic mode beyond 9.3GHz, the coupling and noise are poor.  Attached showing noise floor of the low cost VNAs along with my PNA.  The LibreVNA data was provided (JAN).   From 9 to 9.3G, the Lite is getting much worse and I am guessing the felt this was really the point where it was no longer useful.   

The other problem with that last waveguide is you can see how close the posts are.  It's center frequency is outside of the frequency range of the Lite.   10gGhz is data that someone posted on link I previously provided looking at extended frequencies.   All of the waveguides I have shown roughly follow the WR90 standard which has a cutoff of 6.557GHz.  Because of the limitations of the LiteVNA, we have been testing below the bandwidth ratio (8.2GHz). 

From Microwave Journal Frequency Matters:

Most rectangular waveguides are specified with a 2:1 width to height ratio to achieve a maximum bandwidth ratio of 2:1, i.e., the ratio between the maximum frequency and minimum cutoff frequency. This way, maximum power is carried by the waveguide before microwave breakdown, dielectric breakdown or multipaction can occur. This differs from a circular waveguide since it can only propagate a maximum bandwidth ratio of 1.3601:1, which is the maximum single mode frequency to minimum cutoff frequency. The recommended frequencies of operation for a rectangular waveguide are 30 percent higher than the cutoff frequency and 5 percent below the cutoff frequency of the next higher mode.

It's a tradeoff and because this thread is just for the fun of it we can experiment as we like.  I don't think you will find waveguides made from PCB in the wild nor people trying to use a $120 VNA to measure them.

[joeqsmith]

To get around this hurdle, we will need to use the LiteVNA in a region where it has better performance.  We can then upconvert that signal to something more useful for experimenting with our waveguides.  We can then downconvert that signal to something the LiteVNA can measure.   For S21, we can do this directly or for S11, we can add a coupler.   Of course the software would need to support this.   In 2003, I made such a system to extend my first VNA beyond 3GHz.   Results were poor at best as my 20 year older younger self wasn't very smart.  Not much has changed.     

Because the software I wrote for the LiteVNA is basically this this same software it has always supported adding mixers.  A few of you may have seen where I demo'ed this with the original NanoVNA.  I think I was somewhere in the GHz range with that.

[joeqsmith]

Over the last few days, I have been working on a simple converter for the LiteVNA.  I plan to use my old YIG for the local oscillator and the rest is just splitters, mixers, amplifiers and filters...

To date, Copper Mountain Tech, Keysight, Rohde Schwarz and Anritsu haven't knocked on my door offering to donate any equipment to my channel and because my home hobby budget prevents me from buying any high end equipment, we are pretty limited on how to test it. 

Thanks to members of this group,  I was able to extend the frequency range of my old PNA to 9GHz. 
https://www.eevblog.com/forum/testgear/agilent-e8357a/
The standards I have are not up to the task to measure down to the hairs on my butt cheeks but for these experiments, I think we can ignore that.  Thanks to  rf-messkopf, I was able to at least characterize them to 6GHz.  As mentioned, with the extender we can only look at S21 and are limited to normalization.   

Attached showing our homemade waveguide filter running on the LiteVNA up to it's 9.3GHz limit (Brown) using the provided standards and ideal model.  Red showing our PNA with my home made characterized standards and best load I have available.    Black is the same LiteVNA with my extender, sweeping all the way to 10GHz.   

The LiteVNA is pretty decent to 4GHz.  The YIG is limited to a bit over 8Ghz, allowing us to measure over 12GHz with this setup.     

[joeqsmith]

Being lazy,   I have been using Dennis G. Sweeney WA4LPR's Waveguide Filter Synthesis Program Version 1.3 to pick values for the filters shown.

Attached are the parameters I entered for the third filter.   Rather than buy any tubing to get closer to the recommended values, I used what I had on-hand.  The BW came out very close to 150MHz.   Center is off a bit which could very well be my eyeballing the extender's frequency (too lazy to hook up the counter).   The bat ears may be from the far off tubing sizes.  The first two filters include tuning stubs which were left off.

So far, the cost of the two antennas with coax, three filters and polarizer was maybe $60.  $22 in brass bits and the rest connectors.   LiteVNA was $120.  Add $150 for a better load, home made cables and adapters.   Many of the bits for the extender had come from eBay many years ago at reasonable prices.  Not sure what it would cost today.   

Hopefully I've shown you that you can play with this technology even on a budget.   Merry Christmas.

[joeqsmith]

I would like to test the waveguides closer toward 11GHz but the noise of the LiteVNA increases.  To work around this, I plan to mix with a higher frequency and use the lower sideband.  The software already supports it.  However this was the first time I ever tried ti use it in 20 some years and discovered a software bug when creating the Touchstone files (freq must increase).  Onto version 3.14.

Another problem is I am really limited on bits I can use as a sanity check at these higher frequencies.  For example, shown are three different 3dB attenuators.  One is a Mini-Circuits VAT3 rated to 6GHz.  One is from a really low cost Chinese set.  The last was a pull from some test equipment I had scraped.   These were swept from 8GHz to 11.5GHz.     

I have some attenuators from Midwest Microwave rated speced to 18GHz.   The second picture shows stacking 10dB attenuators while sweeping from 11 to 11.9.  These are all from the same lot and we can see the phase change as we increase the length.

[joeqsmith]

It seems that many of the training kits that were used at the universities/colleges used a fixed frequency oscillator.  This kit for example uses 10.425 GHz.  Mine uses 10.514 GHz and uses the WR90 standard. 

https://tecnoedu.com/Download/56-200.pdf

Using the Lite to sweep from 8-12GHz,  with two back-to-back transitions and comparing that with adding a 0dB attenuator between the two causes a fair change to S21.   In the region where they operate the kit, its stable within 1dB. 

[joeqsmith]

Looking at the slotted line with the probe removed compared with the attenuator set open.  Both parts appear to use the same slotted waveguide sub component.   

Not as stable as I would have expected. 

[joeqsmith]

Inserting the pin into the slotted line then moving it full left vs 18mm. 

Recording S21 while moving the slide from right to left.

Finally, leaving the slide fixed and normalizing the data and letting it run for several minutes, we can see the setup is fairly stable.   

[joeqsmith]

Adjusting the attenuator from 24dB and normalizing the data with the attenuator set full open.   

[joeqsmith]

Microwaves Part VI - Test Equipment & Frequency Conversion
October 1949 Radio-Electronics Article
https://www.rfcafe.com/references/radio-electronics/microwaves-part-vi-radio-electronics-october-1949.htm

Microwaves Part IV - How Waveguides Are Joined and Tuned
August 1949 Radio-Electronics Article
https://www.rfcafe.com/references/radio-electronics/microwaves-part-iv-radio-electronics-august-1949.htm

***
Another interesting article after bands were provided for amateur use.   The attached photo is from the article showing a home made waveguide.   I thought mine were bad.

Microwaves for the "Ham"
August 1952 Radio & Television News Article
https://www.rfcafe.com/references/radio-news/microwaves-ham-august-1952-radio-television-news.htm

[joeqsmith]

As I continue to search for used waveguide parts, many in poor condition, I wonder about lapping their mating surfaces.  Seems like with a flat surface and a bit of wet paper, you could restore their flatness.   

For coaxial adapter storage, I have a wooden box that I drilled out with various sizes to keep them separate.   For the smaller ones, I use ammunition cases (very low cost).   With the waveguides, I see most new parts are supplied with protective caps.  I am trying to locate a source for these caps but so far my Google foo is letting me down.   

https://edadocs.software.keysight.com/kkbopen/how-can-i-order-replacement-protective-caps-for-waveguide-flanges-577940541.html

[coppercone2]

well since its soft

[joeqsmith]

I haven't checked for a flatness spec yet to see what would be required.  Profilometer? Shinny != flatness. 

I did put a video together showing some of what I have been doing with them.   

[coppercone2]

thats looking really nice, I want to play but I need to finish a few repairs because I am annoyed at having too many equipments that have partial function and or are on the fritz . Feel so much better working in the lab after the equipment has been gone over instead of trying to remember which displays are lying, which knobs don't work right  And I need to make a wooden case for some RF stuff. Made like 4 storage boxes last year but I need more.

[joeqsmith]

Not bad when you consider that my investment for all the waveguides shown so far cost me maybe $100 and that was mostly connectors.   Nothing yet deserving of a nice home made wooden box.  Instead they all fit in a Digikey cardboard box with the original paper packing.      

[coppercone2]

I make them out of a enduring stockpile of old cabinet doors etc

[joeqsmith]

All the better when the materials are free.   

Post a few photos of your work. 

[joeqsmith]

Applications of waveguide and circuit theory to the development of accurate microwave measurement methods and standards
Beatty, R. W.

https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph137.pdf

[joeqsmith]

I have ordered new matching pads to try and improve the dynamic range or our extender along with a new sheet of brass to make one last waveguide for the next set of experiments.   

Someone had posted a comment about The Signal Path channel making a video on 3D printed waveguides.  The attached link takes you to what I believe they were referring to.   He made a few horns and a filter.   He's experimenting at much higher frequencies than I am and surface finish.... I would suspect will be much more problematic.   Where I had posted a fair bit of data showing the effects of adding my PCB horns,  we don't get see anything like that with his experiments.   
 
https://youtu.be/bo8pQmKgwgw?t=1966

I would think in the X-band where I am experimenting, plastic 3-D printed parts could be an option with a bit of prep work before coating.  Then again, I'm not sure about tuning them.  I couldn't find where he made a follow on video but certainly an interesting topic. 

[joeqsmith]

Interesting article on 3D printing horns.   They are using solvents, epoxy and files to try and improve the surfaces.  Shown with a professional 3D rotor and chamber.   

https://antennatestlab.com/3dprinting

Most of the articles I have found on printing waveguides, use metal.   

Looking at designs people have uploaded (I was surprised to find any!),  this one is a student.  Maybe we will see some test data from them in the future.
https://www.thingiverse.com/thing:1290578

[joeqsmith]

Here's the last homemade waveguide I plan to construct using these techniques.  Not a bad use of a c-note.   

[joeqsmith]

Another possible coating for printed parts.

https://sandstromproducts.com/products/conductive-coatings/

[joeqsmith]

Test horn #1.  I may need to do a part 3 where we have a horn shootout.   Expensive production vs homemade PCB vs 3D printed with various coatings....

[coppercone2]

oh they have a bunch of prints for this one now
https://www.thingiverse.com/search?q=horn+antenna&page=1&type=things&sort=relevant

I have the MG chemicals nickel spray paint that I was going to do this with one day.

[joeqsmith]

The Signal Path video shows them using MG's copper silver.   They offer an even more conductive coating. 

Hone#1 was from that first link.  One was a WR90 which is what I show.   I saw some on thingverse where they had printed the transition with the horn.   I'm not sure how you would coat something like that as one solid part.   Even that WR90 horn I show isn't the best solution for coating.   You have to somehow apply a coating inside the waveguide. 

[coppercone2]

thin it down and dip coat, or print as 2 pieces and coat them and then glue together with conductive epoxy over the coated flange., it should be OK with the high conductivity MG chemicals epoxy maybe. And give it some lashings on the outside to hold it together with fiberglass or something

https://www.amazon.com/MG-Chemicals-Conductive-Extreme-Conductivity/dp/B018AAT4VC

you got a gallon of that paint right? And my experiance with dip coating is just bad, like with varnish for transformers, it ends up looking like crinkly ass. Maybe if you made a hoist that uses a slow motor to actually slowly remove it from the liquid... I think the idea is that the layer of the paint in the dip coating tank is like a... accumulator of excess paint on the surface of the material, so if you take it out really slowly, it 'wicks' the excess off and keeps it even. Very hard to do with just your hands even for a small object, you need at least I think a pully and a spool to slowly lift it up. I think various dip coating guidelines say like.. 6 inches per minute (thats for red insulating varnish). If you can some how thin the paint down to be like laquer maybe you can use that as a base line. IDK how well conductive coating thin or if they even work after thinning though. And I think you want to align the object so its not pendalum motion during retraction and its very parallel to the liquid layer.

need the pizza guy to figure this one out

[coppercone2]

actually for dip coating a small object, gluing a dowel to it and putting it in a full sized drill press might do the business. I mean it won't be perfect but you can retract the quill rather slow without building anything, and it has a adjustable table. If you had a very slow power feed on the drill press that might be close to ideal?

Maybe putting a wall clock against the handle to follow the second hand would work. Or a projection of a clock or something, like tie a laser pointer to the handle so it aims at a wall clock and rotate the handle so the laser follows the seconds. 

Or maybe there is no upper limit and 1 minute per 6 inches is just a reasonably fast number, so go as slow as possible.

I tried with pliers and plasti dip and transformers + varnish and usually it came out like total garbage, with transformers I don't care too much though, I just textured it a little with a towel. I associate the process with mega bad smells, a mess, general failure and disappointment.

[coppercone2]

btw does that stuff even paint well? I had bad luck with painting 3d prints, it was kind of dodgy. I ordered a special plastic primer once but they said it was out of stock after a month and I gave up

and maybe a good way to resurface the object is instead of lifting it, to keep it suspended, and then drain the container with a small hole, the level should drop consistently .

[joeqsmith]

Some of the printed WGs I looked at snapped together allowing you to apply your coating inside the tube.  The epoxy you listed may be a better solution to joining them.   

The datasheet I linked has a section on application.  It's thinned with water and applied with a gun.   That's a one pint sample container.  Doubt it's any good now with the limited shelf life.  I plan to check it today.  Looking at production parts, some are plated copper.  In some cases with silver.  I image if you attempt to hone the mating surfaces, you may remove the plating.   

After playing around the last few weeks, I think at these lower frequencies, we can get away with fairly crude practices.  You're not going to get much worse than what I have shown so far.   Then again, I've currently got the grinder out.  Not a very scientific approach.      

[joeqsmith]

Waveguide flange dies:   
https://www.ebay.com/itm/144459117195?hash=item21a26f328b:g:kDAAAOSwJoViLOIg

Horn:
https://www.ebay.com/itm/144362628892?hash=item219caee71c:g:RyIAAOSwMMZgkyPR

Looks like they have several components that would have been supplied in the university training kits.  Here's a cavity, brand new, plated but not complete.
https://www.ebay.com/itm/144364961251?hash=item219cd27de3:g:IccAAOSwY45UL~nr

[joeqsmith]

Coppercone2 = coppercone? 

Doing a search on EEVBLOG for other threads on the topic:
https://www.eevblog.com/forum/rf-microwave/waveguide-high-frequency-(past-rating)-behavior/

[coppercone2]

yeah changed my email or something, i forgot

[joeqsmith]

Wanted to provide a little more data for my poor man's frequency extender for the LiteVNA.   I started out measuring the LO with my counter but then a homemade slotted line to measure the extended Port 1.  I also repeated my stepped attenuator test to prove out the input stage.  There are a few other experiments along the way. 

[coppercone2]

for that slotted guide, I think I would put some thin gauge brass springs (like a caliper) under the movable part, so when you insert it, it spring loads itself into position. I am not sure if you did that, but the mechanism sounds a little loose. Spot welder seems useful, my mind goes towards repurposing the leafs in a banana connector to act like a slide spring.

I think I also have some section of brass finger stock some where (RF gasket) which I never used because it was annoying to attach to stuff, but since my spot welder finished I have been meaning to try it for something.

I think there is alot of fun to be had with etching thin brass parts for making weird stuff (i.e. diy rotary joint).

#1 obstacle to working with sheet metal : clean all the work surfaces to more then 5x5 inch space 

[joeqsmith]

The problem with making things more complex than they have to be for a one off experiment, it wastes a lot of time.  The bits I have put together just have to work well enough to demonstrate the basic ideas behind them.   

The original WG consisted of just the slot.  The Teflon sleeve kept it centered.  I added the copper guides to help keep it aligned so I could add a pointer and scale to make the measurements.  I wasn't even going to have a scale but rather just mark it with a grease pen and measure it with calipers later.    Then I wanted to show the ferrite and needed to be able to take my hands off the probe. 

The best solution, hook up the microwave counter with it's GPS reference and measure it directly.  Forget all that mechanical stuff from days gone by.  But the series is about waveguides.    

[coppercone2]

I think there are fast general techniques with standard parts/blocks to make these sort of things work better with minimal effort but there is no good guide on how to do it. I wrote it because someone might follow you and if they know some neat trick to add features with 2 minutes extra work using clever equipment/etc, it might make evolution occur, maybe someone can make cheap advanced DIY machinery if there is a few possible improvements listed... and it gives someone a reason to repeat your work with small modifications because its easy to just think there is nothing left to do there and its done unless you wanna shell out hard core with the castings, heavy duty electroforming and machining. There is an appeal to light duty brass working making this stuff, especially if it can be made better. I think its actually accessible without having to get serious training in 'related fields' .

[joeqsmith]

I think outside of making some very simple parts like I have shown in my experiments so far,  you would be very limited using the techniques I've used.  I think for the these lower frequencies, 3D printing has some merit.   You may be able to control the dimensions tighter than beating on brass with a hammer,  make more complex shapes, include standard flanges allowing a hybrid approach.   

The attached link is a paper on directly plating conductive plastics.   One example they show is a horn.   The surface finish is very poor for the band they are attempting to work in.  We have some different plastics on-order now and plan to compare a few different approaches.   If I can find a combination that I like, maybe we can try printing some more complex shapes.       

https://people.duke.edu/~bjw24/Publication98.pdf

I'm not so sure we couldn't plate the higher resistivity ESD plastics as well using higher voltages.   Lot's of experiments to try....

[mr ed]

Mcrowaves are fun even beyond what the vna can do. Some uwave things do cost but gunnplexers can be had new for $100 on digikey, used much less. You can also make waveguides and horns by hand if so inclined. True, performance wont be similar to a Sage gold plated machined and polished guide but you can still experiment plenty. Attached are some home made horns for 25GHz which work well enough. I use solder paste, brass shim stock, tin snips and a torch.

[joeqsmith]

Nice looking horns.  Measuring the speeders in the neighborhood? 

Found an oscillator under modules but no gunnplexers.

https://cdn.macom.com/datasheets/MACS-007800-0M1R00.pdf
https://www.digikey.com/en/products/detail/macom-technology-solutions/MACS-007800-0M1R00/12627111

[LaserSteve]

Take a look at " SWR Autotesters"  on Ebay.

Steve

[mr ed]

Gunnplexer   MACOM   MACS-007801-0M1R10

https://www.digikey.com/en/products/detail/macom-technology-solutions/MACS-007801-0M1R10/12627587

[joeqsmith]

Thanks.  Here's the datasheet.
https://cdn.macom.com/datasheets/MACS-007801-0M1R10.pdf

[joeqsmith]

Printed horn after wet sanding and primed next to metal horn.   New filament in foreground.   Lot's of prep work left.

[joeqsmith]

The plan is to start with the two short PLA horns from the on-line site I linked.  One with the raw printed texture, the other wet sanded.  Both will be coated.    Then I plan to try copper.   Depending how this works out, I start working with the larger horns then onto other plastics. 

[coppercone2]

I forgot I had a WR42 adapter. I will try a WR42 horn

oh god, free cad programs. I might resize it after I get a degree in computer science.

[joeqsmith]

Nice. Post some pictures of your setup once you get going.

[coppercone2]

the problem is going to be figuring out how to resize this crap. IDK why they don't put a percent resize thing, instead its gotta be some crazy shit

Actually I think I had a program that has that on the other PC, I will look at it some time.

[joeqsmith]

the problem is going to be figuring out how to resize this crap. IDK why they don't put a percent resize thing, instead its gotta be some crazy shit

Actually I think I had a program that has that on the other PC, I will look at it some time.

Resizing, software?  Must have something to do with the adapter you mention.     

[joeqsmith]

I was asked about using automotive copper head gasket dressing to coat the waveguides as a cheaper source.   I have a few different ones I use.

The problem is the carrier is not going to allow the copper to form a bond and it will remain an open.  The material also stays soft.  It may be cheaper but I doubt you will get any performance from it, not to mention, you may not want that sticky goo all over your equipment! 

[joeqsmith]

Even after several hours, you can see the copper gasket material is still soft.  Once the engine were run, some of the dressing I use will harden but I don't think our plastic is going to like those temps.

[joeqsmith]

Mixing up some solution to attempt to directly copper plate our PLA filament.   Better to start with something small that I know we can plate, like a nail.   Sanded it down and cleaned it with IPA.   After rinsing with water, looks like copper.  Note the end of our wire...

[joeqsmith]

Before attempting to plate a large horn, better to run some tests on a section of filament.   This conductive filament is over 1kOhm at an inch.  So I am using a 50V power supply.   I started out around 40V for about 5 minutes.  The problem is the plastic gets warm enough to get soft and would most likely deform.   

You can see though it does plate.  I measured about 20mm of raw vs plated and the resistance is about 1/3. An improvement but still poor.

[joeqsmith]

Back into the bath running around 20V for another 10 minutes got it down to 20 ohms.   Still not great.

[joeqsmith]

I reattached the wire around where the plating had started and continued at 4V for another 10 which got me down to 4 ohms.  Then another 10 minutes which got me down to 2 ohms.   

Shown uncleaned, you can see the shiny copper where the clip was attached.  Maybe the conductive paint performs better.

[coppercone2]

Well there is no horn for that wave guide size ready for download, just two examples.

Good luck with the plating BTW. I figured out I need a hull cell to get any consistent results and that is a ways off.  That is a complicated operation IMO to monitor the solution quality also, you need lots of stuff for good results.

[joeqsmith]

Now I'm with you. 

The coating arrived and I sprayed down the smaller non-conductive PLA horn that I had wet sanded and primed.   Pain to spray into the rectangular section and may try brushing.   Making complex parts this way will require a split.  This part has been drying for about 7 hours but it's humid and cold here.  It will need more time to cure.  Still for the first coat, it seems promising.   

I also sprayed the raw printed part. The coating adheres much better to the primer.    Depending how these two compare will determine how I proceed.   

[coppercone2]

gold plated probes would be good for testing weak substrates like that. And for tests on samples you can glue copper foil pieces (electrodes) to different parts of the circuit and then plate it with wires coming out, so you can can probe directly under neath. I am suspicious of that measurement being off because of high contact resistance.  EEvblog has a video that shows how much better gold probes are for testing dodgy surfaces.

I am not sure if those are gold probes or if its reflection from the copper, but its good information for other people that might have missed it.

[joeqsmith]

https://probemaster.com/8000-series-kits/

Still, not a good meter for measuring low resistance but the question is how it radiates compared with others.   

[joeqsmith]

Discussion of Errors in Gain Measurements of Standard Electromagnetic Horns
R.W.Beatty

1967 National Bureau of Standards

https://www.govinfo.gov/content/pkg/GOVPUB-C13-61d10f6b178c42c8794fe546fc9a7700/pdf/GOVPUB-C13-61d10f6b178c42c8794fe546fc9a7700.pdf

[joeqsmith]

Two new sets off a different printer arrived.  Standard PLA and ESD safe.  The ESD plastic has a very high resistance and I doubt could be directly plated based on my previous experiments with the conductive plastic.   

Front left black is the wet sanded, primed, 2 coats of conductive spray.  To the left of it is the orange is raw printed, no primer and 2 coats of conductive coating.  Once these dry, we can get started. 

[joeqsmith]

Plating one of the test horns.  Different donors for different areas.  Plan to plate the flange, then the WG tube and finally the horn.   

[Kosmic]

Apparently if you hookup your part to a motor and have it rotate in the solution, the coating is supposed to be more evenly distributed.

Ex: https://youtu.be/vsrlrH3omZc?t=287

[xrunner]

Be interesting to experiment with conductive PLA for your project. I have no idea if it would work for waveguide but might make for an interesting investigation -

https://all3dp.com/2/conductive-filament-brands-compared/

[coppercone2]

figured out what the hell was going on, I am printing a WR42 horn now. I had the wrong programs but the abandoned workstation was setup properly so I got that done. Cleaned up the rubble around my work area after completing a few repairs, it looked like a shelf fell over lol

[coppercone2]

I put the setting 3 for height of the horn section and 4mm walls

What I don't like is the 90 degree corners on the flange. Paint on a 90 degree corner sucks. I think it would be good to add a copper shim under the flange with the flange dimensions that has bends that go into the hole, and glue it in, then paint over that. If its thin enough it should not matter. I figure I can print just a few sections of the bottom piece to have a object to form thin copper over before transferring it Or gently rounding the corners with a very fine file.

I mean print out a waveguide slice, then put foil over it wrapped inside to mold it correctly (cut an X into the foil with the dimensions of the rectangle and bend inwards), then glue it to the real horn, then paint that over. There will be a bit of uglyness at the corners of course, but it might be a more reliable transition then just having paint going around a 90 degree bend into the flange. With very thin material it might be comparable to the paint layer thickness. I imagine if you work carefully 95% of the flange bend will be covered by foil, so your paint-foil interface will be triangles on the interior of the horn that are about 0.5cm high, and the flange to flange connection will be 100% metal, so you don't need to worry about screws cracking the paint. And having a subsurface copper shim that has paint on top of it, is IMO much better of a transition, then clamping a wave guide to metal paint. At least there is some kind of chemical bond going on there between the conductor and the paint, not a metal to paint bond mechanical bond. So then there will be a metal to metal bond at the flange interface and then a paint to metal chemical bond on the interior of the horn.


Past that you would need butt joints on foil to make it better I think..... guess you need a shrink ray to do that one.

[joeqsmith]

Be interesting to experiment with conductive PLA for your project. I have no idea if it would work for waveguide but might make for an interesting investigation -

https://all3dp.com/2/conductive-filament-brands-compared/

I have been.

Paper discussing using it for waveguides with one example being a horn
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4642243/#msg4642243

My first attempts to directly plate it (also following two posts)
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4648288/#msg4648288

[joeqsmith]

Apparently if you hookup your part to a motor and have it rotate in the solution, the coating is supposed to be more evenly distributed.

Their two plates may help as well, plus the larger tank. 

He talks about using constant current which I think for the conductive PLA, this is how it will need to be done.   

[joeqsmith]

...
I mean print out a waveguide slice, then put foil over it wrapped inside to mold it correctly (cut an X into the foil with the dimensions of the rectangle and bend inwards), then glue it to the real horn, then paint that over.
...

One way would be to use foil tape over the entire surface.  I think for simple shapes, like horns, this would be fine.  That or using PCB material or bending metal.

I would like to find a 3D plastic print process we could use with more complex shapes.   

[coppercone2]

oops, I put it so the horn is supported by the flange base, so that part is ugly because of all the supports and requires flat sanding etc. I think it will need to remain in the printer over night till I buy some more denatured alcohol to spray it down with.I was thinking how to prevent aperture distortion, not surface finish on the faces. If you put it side ways you get possibly a different problem with warping, which is much harder to deal with, so maybe its the right call. If you print it large apature down, then you either need internal supports or no supports, which I don't like either.

[joeqsmith]

All of mine were printed with the flange on the bed, horn pointed up. 

[coppercone2]

yeah but I put supports. I also had a small crack happen on the flange when I was removing supports. I think I can do this without supports, but I think I Can also sand and patch this one with some epoxy putty.

If I print another without supports I can compare them to see how much they do for all the problems they cause.

[joeqsmith]

Shown is a closeup of a raw PLA print.  All parts were printed without supports.   

One of the first tests will wet sand and prime one horn and leave the other raw.  You can see it's not quite finished in photo.

***
Looks like the drag and drop photo attachments is once again not working.   

[msat]

Thanks for taking one for the team and trying the copper gasket spray, Joe. I never used it on anything other than a head gasket, and that was long ago, but I recall it applying a very copper-looking coat, and none of that aqua-colored slime from your pics. Strange. Do you recall which product you used? I also wouldn't have expected it to provide a particularly robust coating, but hopefully good enough for a bit of testing as long as you don't get too touchy-feely with the stuff. Electroplating is definitely a better option, if a little more involved.

edit:
I only skimmed through this thread after you referred to it in your yt vid, so I haven't looked at the reference you used for electroplating, but in the past I looked up some blogs and videos about plating 3D printed parts in general. Some of the results looked quite good.

Thought about using a friend's SLA printer and even came across some low resistance resin in the neighborhood of milliohms per square, but it was like $500 a bottle 
Even if that borderlines too high a resistance, I bet it would take electroplating pretty well. but that price..............

[joeqsmith]

That was some spray-on Permatex.  I checked the other stuff I have and it wasn't copper based.   If you find something that can be applied to plastics without damaging them,  is mechanically stable, highly conductive and cheap, let us know.   

There is a conductive plastic that has MUCH lower resistance that the stuff we are playing with.  Cost is about $200 for a small spool.  Enough to print one horn.   MG Chemicals also has what appears to be a better coating at about $200 a can.  Both could be a bust.   

[joeqsmith]

Measuring the small PLA ESD conductive horn.   I don't think we would see much gain from it, if any....

[msat]

I thought I came across gasket spray that looked like it might have had some promise, but I must have been mistaking. 

I guess this ultimately comes down to what skills/abilities you have, what tools you have access to, and how much cash you have to burn. Obviously It doesn't really make sense to spend a lot of money on fancy filament/paint/resin when it approaches the price of pre-made hardware. Yeah, the Pasternack stuff tends to be expensive even on the used market, but various parts from things like microwave links can be had for pretty cheap (for less than $100, I got TX and RX amps, two filter waveguides, circulator, and two coax to waveguide adapters). For homemade parts, you probably can't get much cheaper than your PCB builds - even if you had them come pre-cut from a Chinese board house, or your bent sheet metal parts.

Since we can't [economically] 3D print a part and call it a day, I guess it's a matter of cheapish and effective ways of electroplating. Looks like the Caswell copper conductive paint (https://caswellplating.com/copper-conductive-paint-4oz.html?sku=CCP) is at least a good base coat for electroplating (which is what they basically market it for) at a reasonable price - $50 for ~20sq/ft. It's recommended to be sprayed on using an airbrush or or preval (though that might end up being wasteful). Meaning an additional $50-100 for an airbrush kit.

[coppercone2]

well working with the mg chemicals conductive paint can is a nightmare to say the least. I put a nasty coat of conductive paint on it. probobly should pour it out of the can and apply with a brush, or just try a dip coat. I think you can use a trash bag twister tool and a drill press to make a slowly rotating dip coating apparatus also. dodgy is the word.

[joeqsmith]

I thought I came across gasket spray that looked like it might have had some promise, but I must have been mistaking. 

You may have.  I imagine there are many products available but manufactures don't typically provide a spec on how conductive they are.  So you would need to buy and test them.  May cost you a fair bit of money to try them and you may not find anything.

I guess this ultimately comes down to what skills/abilities you have, what tools you have access to, and how much cash you have to burn. Obviously It doesn't really make sense to spend a lot of money on fancy filament/paint/resin when it approaches the price of pre-made hardware.

And may not perform as well, assuming that's a goal.

Yeah, the Pasternack stuff tends to be expensive even on the used market, but various parts from things like microwave links can be had for pretty cheap (for less than $100, I got TX and RX amps, two filter waveguides, circulator, and two coax to waveguide adapters). For homemade parts, you probably can't get much cheaper than your PCB builds - even if you had them come pre-cut from a Chinese board house, or your bent sheet metal parts.

Making complex parts from PCB will have some drawbacks, like soldering.  The board house would need to be able to plate the edges.    Having shapes inside the tube would require soldering on the inside.  Seems like a bad idea.   For a simple horn, certainly doable. 

Since we can't [economically] 3D print a part and call it a day, I guess it's a matter of cheapish and effective ways of electroplating. Looks like the Caswell copper conductive paint (https://caswellplating.com/copper-conductive-paint-4oz.html?sku=CCP) is at least a good base coat for electroplating (which is what they basically market it for) at a reasonable price - $50 for ~20sq/ft. It's recommended to be sprayed on using an airbrush or or preval (though that might end up being wasteful). Meaning an additional $50-100 for an airbrush kit.

The verdict still out on that one. 

[joeqsmith]

well working with the mg chemicals conductive paint can is a nightmare to say the least. I put a nasty coat of conductive paint on it. probobly should pour it out of the can and apply with a brush, or just try a dip coat. I think you can use a trash bag twister tool and a drill press to make a slowly rotating dip coating apparatus also. dodgy is the word.

Without seeing your process and results, it's hard to say.   If the 3D print or the prep work is poor, the coating is not going to correct that.  There could be a chemical compatibility problem as well but I assume you started out with a test sample.   

The biggest problem I see is you are working with WR42.  There are a few reasons I am starting out with WR90 to get a feel for some of the basics.  Construction is certainly part of it.   

Last would be your level of expectations.  Because I have no idea what yours looks like,  I have attached a photo showing a closeup view of the coated surface for one of my non wet sanded test horns.   This should give you some idea of what to expect.       

[coppercone2]

the problem is the can. I renember it was dodgy when it came in, when I looked at it last night it had crust formed on the sprayer, so I  tried to clean it out with a brush and some paint thinner, and put a new sprayer on it, but it was like working bad and soaked my gloves. Maybe its defective from distributor. You also need to shake it very frequently compared to normal paint, and the pressure is pitiful. But for a $40 can of spray paint thats really bad IMO. I remember last year when I tried to paint a sample piece it was also basically bad. I think what happened is when I first used the can, after using it, it got stuck on, and I took the sprayer out and cleaned it out with paint thinner and left it there, then loosely reinserted the sprayer,  but over a year it got crusted over... (but I have paint cans (rustoleum) next to it that are 3-5 years old, while rusty, they have 0 problems). The ESD dissipation paint spray can I got from MG chemicals a while back too also had poor performance (for resistor lead bender project). They have something going on with their spray cans.

I just would have thought for such a expensive product they would make it a little better, because 5$ cans beat it that are 4x older).

I bought some paint brushes so I can rework the feed to the horn because a bit of paint accumulated in there and when I was cutting it off to make the apature rectangular again, I left some bald spots, so I will sand it with a stick and repaint that area by hand.


But the resistance from MG chemicals nickel paint seems low, from the front of the horn to the rear flange (fully coated on both sides), the resistance is <1.5 ohms, but I know that having non conductive spots on the rear feed channel of the horn will be bad, but repainting a square centimeter by hand is not the end of the world, I got a set of tiny brushes that have a head the size of a match head. I was initially going to try with a Q-tip but I thought to just get some brushes lol


I maybe recommend if you get MG chemicals products, just buy it from digikey, not the cheapest distributor.

tldr: bad experience in general with MG chemcials spray products but fine experience with other products.

I need to make a tiny sanding stick, which I am not looking folward to.

[coppercone2]

also for the next horn I will try to see if I can make the copper foil feeder/flange, so the paint cover near the feed is not as critical.

[joeqsmith]

I've been shaking the can a few minutes before using it each time and a few shakes along the way.  End by flushing the port.  Thin coats.  I wouldn't expect these metal coatings to act like paint but so far, that is how I treat it.  There has been no signs of it clogging.   Shelf life for the one I wanted to try was one year.   Not sure what the MGC is.  They don't seem to publish it. 

Resistance will depend on coating used and thickness.  Attached showing one of the large test horns.   You can see my first measurement was 2.6 ohms.  I added a few more thin layers to get it down this far.   Dots mark where I measured it.  Note it's fairly consistent.   I never tried the copper foil tape.  It will be interesting to see what you come up with. 

Also shown is a test print made from the conductive plastic I had attempted to directly copper plate earlier. 

Slowly getting everything together.   

[coppercone2]

thats looking good. I plugged mine into a 8510C VNA for SWR plot.

It looks like under 15GHz the SWR is very high, and it has a sine wave pattern, and of course I did not calibrate it. But I see that between, 15-17 its wavey but some areas near 1, 17-20GHz (limit of my test set) the SWR is under 1.8. Won't get good data till I get a SMA cal kit, I will get ome ictures later

But I guess it does work, if I wave my hand infront of the antenna it makes the SWR plot act up like the real horn antenna do. I think you could transmit with it. And I got nickel because it was supposed to shield lower frequenices, so copper is doing much better I see.

It does fufil the criteron of SWR<2 for 18-20GHz (well under 2).


basement is cold right now, dont wanna be down there, and its an obstacle course near the racks

[coppercone2]

take note that if you make the horn thick you have problems with the screws, so you need to use screws which are too small for the hole that is there, unless you cut slots into the horn so that you can slide it in there

I need more couplers so I can try a reception test

[coppercone2]

here is the horn but the VSWR needs a GPIB dump or something, the camera is horrid at CRT

[coppercone2]

I got rid of as much of the flash and backwash/reflections/distortions as possible with ms paint, the scale is 1swr/div and 15-20 GHz span. Renember not calibrated, just stuck a cable and antenna on it. First purple line = VSWR 2. Before 15 its off scale because its out of waveguide operating region

and its just hanging off the side aiming at a wall 10 feet away

[joeqsmith]

take note that if you make the horn thick you have problems with the screws, so you need to use screws which are too small for the hole that is there, unless you cut slots into the horn so that you can slide it in there

I need more couplers so I can try a reception test

One of the first things I looked at were the dimensions of the 3D prints.   Flange and WG dimensions are from the downloaded model.  So far, I'm not seeing any problems. 

When running the horns, I will use the same transition and hardware to remove that from the equation.    I have no plans to look at VSWR, rather just their  radiation patterns with a standard setup. 

Some time ago I showed a similar setup where I used a power amplifier, directional coupler and a mismatched load to demonstrate how to improve the SNR when looking at S11.   I mentioned it would require a change to my software to support it.  A coupler could be added to the frequency extender to measure S11 however there are a few problems.  Lack of standards, lack of a coupler and of course the software would need changes.   

I recently posted in my software thread how Dislord provided me with some new firmware for the LiteVNA that removes the upper frequency limitation. 
https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg4651535/#msg4651535
The new firmware could be used to directly measure S11 and S21 for the horns I am experimenting with, except, as expected, the Lite's performance is very poor in this region.   

I think to experiment in the frequencies you're talking about, I would have to start a new thread, "Experimenting with waveguides using the CMT S5242" 

[coppercone2]

well I plugged a APC-7 cal load into the front and just looked at it to verify the data, from 15-20 ghz its 50-30 ohms, so in some points it drifts at least 20 ohms.

And I forgot I have the 18GHz test set too, but again, not that far from 50 (off by a mile but not the wrong continent perhaps), and the test goes to 20GHz, so that data is of course taken with a grain of salt. I do have proper 18-2something horn type antenna too, but I need a oval to rectangular adapter (last time i bought adapters for wr42 I got something completely different and it left a bad taste in my mouth). It works with just a rectangular adapter for detecting a signal, but I never measured the VSWR.


Probobly not the best frequency range to be messing with, I only did it because I had the WR42 coaxial adapter on hand. Perhaps I can get this sorted.

I can do a cal with an adapter though, but at that frequency its still gonna be not that great. At least i feel up for dealing with this equipment again, after I repaired it I decided it needed a long break because last year it was just not fun to run after all the problems I had to deal with in the sweeper. Honestly its kind of like buying a pegasus galaxy wraith on ebay, try working with it for a while and you end up feeling 30 years older and the equipment ends up being 30 years younger. 

[joeqsmith]

  I plan to live my higher frequency testing through your eyes!!  I certainly can relate to dealing with old test equipment.   You start out buying a "working" used system, that of course, you know isn't actually working.  The word "working" really has no meaning in the modern language.      Then you spend time finding the problems and sorting parts.  Finally you get it all running and aligned.   Then in a few years, something else fails on it.     Assuming you weren't born into massive wealth and have an unlimited budget for your hobby, there's not a lot of options.   

Here's the LiteVNA, no calibration, sweeping 10-18GHz, measuring VSWR of the load that was supplied with it.  I'm not thinking this would work for your case!  But, it is reliable and relatively cheap! 

***
Of course, if you're like me and have lots of used equipment, a fair amount of time is spent maintaining the equipment rather than actually using it.

[joeqsmith]

If we calibrate the LiteVNA using my poor man's standards for the region I am experimenting with these WGs, then attach the same load.  You can see, it's just not capable.   Should be clear that I wouldn't expect it to be.  I'm actually very impressed with its performance for the cost.   

[coppercone2]

well on the plus side, that frequency range does not have much going on there that is interesting. I don't think I would recommend trying to go there unless you really want to or have a reason for it, no epiphanies for use came to mind over a long time. For instance voyager uses S band IIRC, and that is probobly THE most interesting use of signal RF people have found.

And I kind of feel like AI image stuff is going to take over the car radar market, because its much cheaper and basically standard equipment, plus it will be capable of making some advanced decisions eventually compared to radar (i.e. identify cyclist, pedestrian, curb, truck, etc). I guess there is high bandwidth cell phone network stuff, but that is not that interesting since its just going to be a standard data channel. Like are they going to go for buzzwords related to AI and image recognition or MMWAVE MMIC in corporate, I think its the first one. Of course long term the radar related technologies seems like it will win and be better/reliable/etc, but for the short term...

[joeqsmith]

Looks like the ham's use some areas in the 10 and 24GHz regions.   This may explain the problems locating WR90 parts.  I'm envisioning all these old hams hording the surplus WGs, packed away in their basements.  After they die, their kids find it while cleaning out their house and sell it for scrap or it goes to the dumpster.      

https://www.arrl.org/files/file/Regulatory/Band%20Chart/Band%20Chart%20-%2011X17%20Color.pdf

[coppercone2]

https://www.reddit.com/r/amateurradio/comments/daj2nf/ehfshf_operating/

[joeqsmith]

If I cal the liteVNA at a lower range (6-8G) then measure a decent SMA load (red) we get something more reasonable.   Swapping the load for a low end coaxial to WR90 transition with nothing attached and pointed toward the ceiling, we get a pretty high VSWR (yellow).   Using some paper clips to clamp a production test horn to the setup, the VSWR gets much worse below 6.9GHz or so (violet).   

[joeqsmith]

I read through the Reddit link and then read the story linked at the bottom of the thread.
https://www.w9fz.com/superior/index.html

Here I calibrate the LiteVNA from 7.8 to 8.6G (using the poor man's standards) and sweep the good load (red) while measuring VSWR.

Next a good transition is mounted to a known return loss WG standard (yellow).   Even with a 670Hz IFBW, we can't tell the two apart. 

[joeqsmith]

I have added support to use an external coupler with my software.  I placed a high pass on the output of the LiteVNA along with a small amplifier and into the coupler.  Using the same poor mans cal standards and loads,  I swept over the same frequency range using the same two loads as the prior plot.   

Like before, the frequency converter was not used.  Instead we are using the Lite's harmonic mode.   Both the coupler and amplifier are being operated outside of their specified ranges.   


I had to stop all of my 3D printing experiments after I made a bonehead move not wearing a wrist strap and took out my extender.  Its winter here and I knew better.  Thinking, hey, the horn is all grounded, no big deal.  Went to change the setup and touched the horn and zap.  That was the end of it.   

Once I repair my stupid mistake, and finish collecting the data I plan to try using a coupler with the frequency converter.   I should be able to make a decent VSWR measurement of these test horns.   

[joeqsmith]

While I continue to wait for replacement parts to repair my ESD snafu.  I bought some scrap WG that I am cutting up for another experiment.  Silver plated brass with a heavy zinc primer and what appears to be a powder coating.  Much nicer than my hammered out hobby brass.   To the right is a transition I am putting together from it. 

[joeqsmith]

The replacement parts arrived and I swapped out the dead amplifier.  Hope to finish up testing the 3D printed parts in the next few days.   

Also shown is the new home made transition.  Bandsaw and end mill to square it up.  Added a plate to increase the wall thickness.  Should work better than what I have made so far. 

The 100ohm resistor attached to the phase trimmer is used as a sliding load to aid in developing the software to support one.  We should be able to get a decent VSWR measurement of these printed horns. 

[joeqsmith]

Back to testing....

[joeqsmith]

The two homemade transitions getting their last coat of paint. 

[coppercone2]

I got the next waveguide adapter so I can test the antenna to antenna transmission, and I ordered the silver coated copper paint also

[joeqsmith]

Nice.  I'm pretty much finished with my next round of experimenting.  I attempted to measure VSWR for the various test horns as well.   Look forward to seeing how your setup and data compare.   

[coppercone2]

yeah this time I can try to calibrate it minus the adapter, I just need to go through the manual it was kind of complicated, and try to save a data file on disk

[joeqsmith]

I measured VSWR with three different setups and got three different answers!!      Hopefully you have better results.

[joeqsmith]

Video showing the 3D printed plastic horn's radiation patterns and attempts to measure their VSWR.   
 

[coppercone2]

Lol, nice catch with the ESD horn. I was suspicious too when I was working that I might just be measuring the end launcher. I guess its stealth material huh?


I need to get some of those sanding pens. Tried to 3d print one but it kinda sucks. Don't wanna buy those little belts either but its not practical to finish these things nicely without those tools IMO, so I am not screwing around with Popsicle sticks. The problem with the 3d printed sanding pens is that they rely on a strip of material that is wedged under a threaded piece, so you need to thread over sand paper, and also mess with threads to expose fresh sand paper, which gets clogged fast by 3d print material. It looks like the ones that run on a small belt can have fresh sand paper rotated into place and fixed with some kind of tension mechanism. So the DIY ones (in addition to being quite weak) are only good for very small corrections.

BTW lookin at these horns standing around, with the end launcher on, I wonder if the pharos of egypt were thinking something about energy in the earth (maybe they saw lightning hit the ground) and that the pyramid was something like a horn antenna in reverse, that channeled the energy to the top. Because you are starting to look like giza and I would have a problem if my printer was a little bigger. 

maybe there was like a little hunting tree stand on top of the great pyramid back in the day for him to sit ontop of


Because those guys were like the only other people then RF engineers to give a shit about forming perfect pyramid structures. The amount of work that went into leveling the foundation on those pyramids and dragging those blocks. I read some where they had very strict dimensional tolerances for those pyramids, and they used to be covered in some kind of substance to smooth em out. Clay I think. SO they were just as interested in surface finish as we are.

And aint some people say that they were covered in gold leaf or something, that got stolen over the years? Well given the extravagance by those leaders, would not surprise me if that thing got covered in gold. Doubt my wealth? Look at my golden pyramid. (not the worst way to store value either, other then attacting burglars, its easy to melt it back down when there are problems extracting taxes. Maybe solid dielectric filled horn for harnessing telluric currents disguised as a grave. Real reason for success of the egyptian empire : ground radio communications, powered by clay jar batteries or something. Or something to do with lightning. Lay it with gold leaf, when lightning hits, you can gold plate nearby objects via plasma discharge. I wonder what the hell would happen if you turned that pyramid into a 'slapper' detonator lol. Maybe 2500 B.C. sputtered ceramic parts were being made. Would make me feel alot better then mountains of religious crap.

It might also look sick if lightning hit a giant pyramidal 'fuse' material. I think it could have happened, they used to put gold reflectors on top of stuff out in the desert long ago to prevent people from getting lost and also attracting trade merchants, like it was big in egypt if I recall from the documentary I watched a while back (they only mentioned modest mirror sizes). Damn now I wanna know what would happen if you gold plated the great pyramid of giza and it got hit by a big lightning bolt. Aztec pyramids not nearly as interesting because they dont smooth em out.

[joeqsmith]

I don't waste a lot of time discussing flat earth, religion, politics or perpetual motion. 

Sanding wise, I used flat surfaces and started with 200 and worked my way up.  All manual.  As far as being practical, I'm not trying to mass produce these horns nor am I trying to make a horn that I will use.   Rather I am trying to get a feel if we could print more complex parts rather than machine them for running other experiments.       

[joeqsmith]

Ham talking about where all the surplus went.  Makes sense that much would have gone to recycle.

https://youtu.be/j1_yZDN4IEw?t=2247

[coppercone2]

released from cold war agreements.......

I think someone better call the dog catchers on them with what I have been reading in the papers for the last two years. I keep seeing rehashes of the Adams family, Russian aggression and China paranoia. Thought it was alternate reality 1950. And all the... cures.. that got rid of microwave backbone are going bad too, banned compromised networking/comm equipment, extreme ASAT weapons proliferation, rapidly accelerating third world nuclear weapons development (Iran/NK), cyber attacks on infrastructure (and these are the drunken uncoordinated hit with a 'foam pool noodle' kinds) etc.

Heartwarming tale about setting up microwave links to broadcast freedom
https://tech.slashdot.org/story/23/03/08/2224256/taiwan-suspects-chinese-ships-cut-islands-internet-cables#

[joeqsmith]

My attempt make a 1/4 wave offset short for a calibration standard.   Also shown is my short.  Bought a decent load from Narda.

Showing VSWR measurements of the Narda sliding load (1.353) and two of the low end loads from LRL.   

I tried to measure the two LRL loads directly with the LiteVNA.  Shown compared with the data from the old Agilent.   

[0culus]

I have been following along with some interest. It's pretty neat what you've achieved here.  I have not attempted to roll my own yet. However, I recently acquired some more surplus WR-90 waveguide pieces, so I've finally got enough to do some experiments. I also recently acquired a partial HP WR-28 cal kit for a song because some !@$#%@! robbed the precision load and offset shorts (and the floppy disk) out of it. I got three pieces of WR-28 line and the tools though!

[coppercone2]

I removed like 4 garbage bags of rubbish from the basement and cleared most of the tables, ready for another print and to make a little shelf to hang in front of the VNA off the rack. Amazing how much trash repairing that equipment generated. Screws all over the floor, component leads, baggies, q-tips, wipes, solder, sand paper, blocks, sponges, jigs, panels, cut components etc. I just let it accumulate when I was trouble shooting some of the stuff, mixed with furnace parts, plumbing parts and turnings and wow that got out o hand.

Step 1: ability to place cal kit on flat surface instead of broke equipment stonehenge.

[coppercone2]

are you doing experiments with dielectric fill or something btw? looks like a gas syringe.. sf6?


I also wanna make some waveguide stands now when I saw your setup. I wonder how hard it would be to get useful dimensions that interface well with many parts. I am just thinking to glue wood blocks together to make loose fit ones. I hate those long setups with coaxial parts, stuff is ends up floating at weird angles. A good one is like a welding table almost.

Did anyone that worked for commercial endeavors on wave guide have such a setup ? Like a grid/optics table dedicated to microwave parts setup? Once you accumulate enough waveguide parts it seems reasonable to think about development of such a thing.

[joeqsmith]

There was a couple of complete sets of Anritsu calibration standards on eBay for cheap.  One set was for WR90.  The old Agilent uses a 1/4 offset.  The Anritsu set came with the 1/8 and 3/8. 

The stands that came from LRL are nice and heavy.  They have three rubber feet.   Downside, they can't be adjusted, can't fit next to one another with the lip at the base, and of course support WR90 only.   Makes sense as that's what the training kits all used.  ARRA made a much nicer university kit.   You can buy stands, or I've seen some 3D models you could print your own. 

First Google hit:
http://www.lteq-microwave.com/waveguide-stands.html

[joeqsmith]

The Keysight PN# 11664-20021 1/4 shim is 9.78 +/- 0.02mm thick.   

[coppercone2]

What is your bath chemistry? I have gotten copper sulfate

Did you build a hull cell for testing the plating ? (basically a tapered chamber that allows for a field gradient on a single plane to extrapolate plating current)

What I came up with is to make plastic welding easier, is to use a thicker glue to put the cell together out of acrylic, and then place it at an angle then flow liquid silicone in there, let it cure to tacky, then rotate the cell to the next edge and repeat till there is a bead of filler on the inside, because gluing those things tight is hard. For calibration purposes it should hold IMO, only a few hours probobly. And to use thick materials for the base. 4 hour dwell time should seal any gaps with the liquid silicone. I did this for a rather heavy built photo development tray, since its heavy you can sway the liquid with little risk of spilling, if its light you are liable to get splatter if you make a mistake, but it weighs several pounds. Dampens your body movement. For those without a PhD in aquarium building.

[coppercone2]

started the second horn print, hopefully the new spray can of silver paint will work nicely. This time I will paint the apature with a paint brush before I spray paint it, to try to maximize surface quality

[joeqsmith]

Used copper acetate.   I have not made anything beyond what I have shown. 

I thought about running a few samples to get an idea of the thickness, for the skin depth.  Instead, tried a test sample and saw within a few seconds @ 500mA it had taken.  Left the part in the bath for about a half hour and called it good. 

[coppercone2]

[coppercone2]

Have you looked for leakage at those plastic wave guide joints? I plan to test that also, I wonder if there is a need for gasketing or something.

If you hook it up to a low power level (maybe through a attenuator) and place it on a copper sheet, it should have bad reflections but also allow you to measure leakage with another horn. just need to make sure equipment wont be damaged. Would be interesting to know how much is leaking out, rather then just being dissipated on the non ideal surface. If the 'end cap' leaks too much, I guess you need to make a conductive opposite piece to plug the horn with... if it has enough over lap that should work even if not ideal I believe..

I also think I can sand the launcher face from the nickel painted one and give it a silver paint over it. I don't think the paint should be too thick at the interface, but I don't think it will cause too much a problem on the rest of the horn. Definitely want to keep track of undesired exposure...

This might be a good opportunity to test high silver content silicone gaskets. Easy to make a little mold with the bare horn. I think a proper woven one would need to be laser cut or something (I think that material exists, kind of like very fine braid)... maybe they sell specific parts too.

Also had some success cutting the sanding sticks with a exacto (takes a while to cut through the wood strip) to make narrow sanding sticks to try to sand the interior of the narrow portion of the waveguide.They don't sell ones that have a fine grit, so you can use a cutting guide and keep cutting with a fresh blade.

[joeqsmith]

Outside of running spherical sweeps in the far field, no.   As part of that testing, I did compare the printed horns with a production part.   I ran the sweeps using the LiteVNA with my poor man's extender at roughly 10GHz.   

I could certainly take the best horn of the group, tape it off with copper foil to seal it as you suggest, and repeat the sweep using my old Agilent VNA.   It's limited to 9GHz but has a much lower noise.   

I wet sanded the flanges on each horn.   Consider the skin depth and the manufactures thickness for the coating (datasheet) along with how many layers I applied.   I never used any sort of gasket.   Flanges were bolted together.  I did go over the choked flange design. 

Once you have yours built up and tested, let me know your results and I can try to replicate them with my setup.  Keeping in mind, everything I have shown is in the X-band.   I would expect things to get worse at shorter wavelengths. 

[coppercone2]

well the usual happened with MG chemicals spray products, they work like shit. I damaged the horn while cleaning it after a failed paint job because I dropped it, so I would have to make a new one. The can was heated, shook for 2 minutes, and then clogged 1 seconds into the work. Also unlike the nickel paint, this one does not transfer at all with a manual brush, the nickel one you can kind of mis use as normal paint if you are quick.

Now 3/3 MG chemicals spray product (nickel paint, silver paint and ESD dissipative coating) all had severe problems during application, even when purchased from digikey. And leaky cans

Not going to try again until I find some kind of paint product that I like.

There is some kind of problem with surface tension and sharp edges too, but I will not even experiment when the aerosol flow is so dodgy

Only MG chemicals spray product I recommend is alcohol. Maybe someone will figure out a 'consumer grade low skill' spray on product in the next 10000 years. Paint with out metal particles is slightly easier, but still.... they uh... over do the easy portion of this... too much art involved, and the rate of cash flow out of my pocket is way too high when I am misting fucking silver.

And this can only works if you shake it while you are spraying, you have about.. 1/3 second after you stop shaking that it messes with the flow. Maybe if you add a vibra motor to the can it would work better IDK,or you get a musician that treats it like a maraca or whatever, and you get random clumps of silver

The usual shit on friday when you think you can finish something off eh, feel the same way about this as I do about aluminum brazing  :'(

difficulty level > pizza dough

I almost want to try again, but this time rough up the surfaces to 60 grit, and do enough coats to smooth it out, but probobly that will end badly too.

[joeqsmith]

I painted all those test horns with several coats each and have maybe a half can left.   

[coppercone2]

well I dunno, I managed to do the last one with nickel paint, the silver paint is just extra evil. The second I saw what the can did I knew its over

Some people are not good at math or throwing things, but I am not good at dealing with pastes and paints.

At this point a kiln is gonna be cheaper.

[coppercone2]

I think the best solution might be hybrid.

Cast the end launcher in a open mold with a minimum of silver, then glue the 3d printed horn to it with epoxy. Then you can do a sand casting, with a regular 3d print, so long you can machine the top flat. No aperture to paint. The whole thing is hard to cast probobly, and expensive.

Infact I think I can cut the end of basically any wave guide and glue a pyramid to it..

I will see how many ml of silver i need, maybe its small enough that I can melt it with a torch in a small crucible and pour it open into a sand mold made with a 3d print.

[joeqsmith]

My only goal was to get a feel for if 3D printed plastics was a viable option for making prototype waveguides.  The horns were are a simple enough shape to try out.  I have no use for them beyond the experiments shown.   

From my previous posts, attempting to use the LiteVNA to directly measure VSWR, even with the offset load standard wasn't very good when compared with my old Agilent.  When using harmonics above 6GHz, the LiteVNA's performance is just too poor.   When I measured the horns during the video, I mentioned I had used an old Narda coupler and used port 2 for the reflected signal.   I mentioned the problem with this was both the coupler and amplifier I used was only rated to 8GHz and the lower end of the extender is about 8GHz as well.   

Still, shown looking at the two Narda loads with the extender+coupler, compared with using the LiteVNA to directly measure the load.  Using the extender to measure S11 at higher frequencies could be solved with $$$. 

[coppercone2]

alright well I gave it another shot because I had to wait for something to finish nearby,it looks like I got a nasty coat of paint on the interior. If I am able to do a full cure, then very very carefully sand it down a little with sanding sticks, and then maybe touch it up, it can be finished. I think this paint cures pretty quick and its rather tough, so it might actually sand OK. The flange has a chip on it, but that will fix easily.

I am kind of wondering if its possible to texture the horn somehow before printing, and then use a gap filling primer, sand that down, and then paint that.

[coppercone2]

after a 1 hour bake at 72C, it seems to be sanding good with the sanding stick (240 grit). Looks like I need to do another pass at 320 and do a very minor touch up on a pin hole that formed. But on the final coat, I am either going to have to stand it, at least spot sanding, because every time the can leaves a few lumps.

Need to get that plastic parts primer, when I ordered it online before they were out of stock and I keep forgetting to do it.

The nickel spray paint seems like its.. rough after application, it reminds me of galvanzing paint. The silver paint seems smooth on finish, it reminds me more of a clear coat type finish.

I might recommend that if its feasible, to just go with nickel paint for electroplating, the silver paint is harder to apply.

I believe I can try to plate both of the horns I made.


Also, for clear prints, do not paint the outside till you are sure of the inside. You can use a powerful flashlight to see if there is any uncovered areas.

[coppercone2]

Well ok, I put a third coat on it pain stakingly. The wave guide portion is sealed, but there was some pin holes on the flare that I could not seem to seal, even when I was heating with a hot air gun to spot cure the paint and re seal. I dunno why its so hard to seal up, it looks fully coated to the naked eye, yet light escapes some how. Defiantly need primer of some kind for future production.

but as a precaution, I will be putting copper tape on the outside of the horns. It seems like a good idea anyway, incase there is flaking or something, so it does not radiate in the wrong direction. Might be electrically annoying. Or I will just plate them.

It looks similar to the degrading coating put on those black paint covered light bulbs with a apature to direct light in a particular direction. When the paint flakes off because of age, it looks like that.


I don't know if they have translucent materials for your 3d printer joe, but if they do I recommend making a translucent one and seeing how well that paint and plating adheres, if there is any pin hole leaks. 

Kinda wonder too, if its all done, would putting gold leaf on it hurt it any?

[coppercone2]

lol ok, I was just doing comparative tests between the two antennas to see how they effect the reflection. The silver one has slightly deeper nulls and the same general shape. Gremlin attack the VNA though, seems to need to reset the source sometimes when there is a big disturbance on screen (like swapping DUT)

Based on the 18-20GHz range, which is not even in spec of the test fixture, the silver paint one got ~0.3 swr better and the ~ same shape when it was pressed into the coupler without screws, and this seemed repeatable

and it turns out the second adapter I got is for a slightly smaller wave guide, it has no response within the range of the instrument, the seller screwed me. there is some kind of force preventing me from getting this work done, i even managed to crack the silver antenna because I tightened a screw too much

so, their kind of similar and the silver one seems to have a generally very slightly lower SWR response when doing comparative testing, and the SWR is much better then with only the coupler (adding either antenna... levels out some of the hills) . Need another coupler to try transmission though. I can do this frequency better with a external directional coupler and SA/SG,maybe I will set that up later, so I am within the spec of the equipment  and with the new incorrect coupler I can make a even smaller harder to measure antenna (TY ebay).

but hey, at least nothing exploded, pretty happy. Gonna get conductive rubber gaskets though, so I don't risk cracking shit again.

[coppercone2]

BTW its alot to scan through your posts and videos, did you have a before and after comparison of some electrical plot before and after plating ?

[joeqsmith]

Take aways from the last video showing the 3D printed plastic horns.   

1) Only the first horn was left not primed.  Learned that lesson on the second horn.   
2) I allowed the paint to fully dry between coats.   
3a) I saw a measurable increase in the horn's forward gain when going from 2 coats to 5 coats.  Adding a 6th coat I saw no measurable increase.
3b) Lowest DC resistance did not equate to better gain.
4) I saw very little difference when comparing a wet sanded surface with a one just lightly sanded.
5) If you want to measure VSWR, make sure you have some way to validate your setup. 
6) MOST IMPORTANT,  wear a wrist strap!!!  ESD is fierce competitor.   

BTW its alot to scan through your posts and videos, did you have a before and after comparison of some electrical plot before and after plating ?

I don't believe so.  Only the effects on forward gain by adding more coats and some of the ESD and conductive plastics without any coating.   In a few cases, the signal actually attenuated as I assume the uncoated plastic was absorbing some of the signal.   

...  and it turns out the second adapter I got is for a slightly smaller wave guide, it has no response within the range of the instrument, the seller screwed me. ....

   
 
I've searched various sources for used components and it's common that the seller is clueless.   In many cases, the OEM is gone along with the data for the device.   It's up to you to ask detailed questions.  At least with WGs you could ask the seller make some quick measurements to at least let you know if you're in the ballpark.   

[joeqsmith]

Using my homemade calibration standards with the LiteVNA.   The twist, no nut, bolts or clamps were used during the calibration.

[joeqsmith]

Interesting question from viewer Wave64.  Sadly they removed it.   Turns out what they really were asking was why the offset short (guessing the short as well) is a dot rather than an arc.  I'm sure most viewer's who follow the channel know that I have been using ideal coefficients but I suspect that in this case, the poster did not understand what that meant.  Here are a couple of articles on the subject that may help other understand why my setups always show dots after cal rather than arcs.   


https://edadocs.software.keysight.com/kkbopen/when-we-measure-the-open-or-short-reflection-on-a-vna-why-is-the-result-in-arcs-but-not-a-dot-on-a-smith-chart-as-most-people-expect-620142095.html

https://coppermountaintech.com/introduction-to-the-metrology-of-vna-measurement/

[coppercone2]

I love the units provided for the calibration standards, + something  ^-42 henrys

[joeqsmith]

I pulled the specs for the 11664-20021 WR90 shim from here:

https://testequipment.center/Product_Documents/Agilent-P11644A-Specifications-6D081.pdf

With a nominal thickness of 9.78, the delay works out the 32.63ps.   3/8 standard would be 14.67mm 48.95ps.  The Maury 3/8 standard is 14.48mm 48.32ps.   So, a bit of an offset.  If I wanted to tighten things up, I would start by bolting/clamping the parts together.  Then measure the standards depth.  With so many other sources of errors, I see no reason to chase that rabbit.

[coppercone2]

I was actually trying to determine a torque limit for the 3d printed resin parts. Maybe your parts can handle it, but flashlight inspection is basically demanding that I get conductive gaskets of some sort for the interface.

I finally played around with VNA calibration, using the sliding load.. .but of course the antenna is right at the end of the calibration kit.

I need a saturn printer so I can get into lower frequencies without fooling around with glue seams and such, its hard enough as it is to paint these things IMO. Or just settle for shorter horns. Plated loop antennas too maybe.


hopefully a little bit more misering will get me out of this impasse

[joeqsmith]

You could make a metal plate that would wrap around the flange, "U" shape.  Spread out the force. 

I have a few PLA parts that I never did anything with.   It's certainly possible to measure the flange flatness and attempt some sort of flashlight leakage test.  With you working with different waveguides, I don't think it would be very helpful but I'm willing to have a look if you like.   

[coppercone2]

Yeah all I did is just hold a flash light on the other side while its pressed in. I think I need to lap the paint.

The first horn I smoothed out the supports via sand paper and optics plate, the second horn I just used as it was pulled from the work place on the elegoo mars printer, I assume its pretty flat but I did not check, but they dont pass the flashlight test.

Do not look forward to trying to sand that paint because the aperture is in the middle and the paint on the edge is IMO of dubious integrity. Its been cured for a while so I can try a gently wet sand.. the problem I had last time was the sand paper I had curled up and it was pissing me off

I can check the flatness if I buy some of those stupid ass 3.6V AA cells for the dial indicator I have (like xeno cells), because that one fits on the granite block. I got the granite 4 years ago and I aint do shit with it yet lol, 'federal tools' are about as fun to work with as the IRS


I wonder how many attempts its gonna take to get the proper wave guide coupler lol, this whole endevor is pure wrangling. When I installed a garden hose faucet into a brick and cinderblock wall behind a tree I pressed out of the way, which was maybe a 1 hour job, and stretch that into 2 years, its the same feeling. The tree was just bearly small enough to push out of the way if you really really tried hard. (freeze proof faucet that is long). brittle plastic and copper = masonry plumbing 100% similarity

[joeqsmith]

I was thinking to run it on the profilometer (optical).  I have a granite table at home that I use to setup my engines.  My V blocks and table are just big enough to set a crankshaft up on it.  If you just want a ballpark idea of flatness, this would be a very simple check.  I could take a few photos in the dark using the flashlight with  the flange laying on that table while I'm at it.   Maybe run one that wasn't coated and one that was.   

[szoftveres]

Interesting question from viewer Wave64.  Sadly they removed it.   Turns out what they really were asking was why the offset short (guessing the short as well) is a dot rather than an arc.  I'm sure most viewer's who follow the channel know that I have been using ideal coefficients but I suspect that in this case, the poster did not understand what that meant.  Here are a couple of articles on the subject that may help other understand why my setups always show dots after cal rather than arcs.   

I removed it, it was a pointless conversation; the above links didn't address my comment.

A 1/4 wave offset short is a 1/4 wave impedance transformer, transforming a short to open, but only on a single frequency. In the waveguide world, the only way you can present a high-Z termination to a VNA is by transforming a short at a single frequency with a 1/4 wave impedance transformer. Waveguide cal algorithms know about this and compensate for this, and when you re-measure your offset short (or as a matter of fact, any "stub") you are supposed to see an arc, as with any 1/4 wave stub. Except, when your calibration algorithm wrongly assumes that an offset short is a 1/4 wave offset short on every frequency - in that case you get the dot when you re-attach it after calibration.

You can fix your calibration algorithm, by de-embedding, or adding transmission line sections (i.e. compensating for phase), depending on how far you are in frequency (and which way) from the 1/4 wave of your offset short.

I hope this helps.

[coppercone2]

I was thinking to run it on the profilometer (optical).  I have a granite table at home that I use to setup my engines.  My V blocks and table are just big enough to set a crankshaft up on it.  If you just want a ballpark idea of flatness, this would be a very simple check.  I could take a few photos in the dark using the flashlight with  the flange laying on that table while I'm at it.   Maybe run one that wasn't coated and one that was.

well no pressure because our printers are different, I don't plan on getting into extruders any time soon, its not useful data for me other then curiosity. I believe you will have different figures because of

1) build plate heater, I believe you have significant thermal differential in the structure as its being built in a extruder printer
2) thermal contraction of extruded plastic on a local level
3) possibly moisture related stuff

I think there is very little heating occurring in the resin process, its essentially fluid cooled the whole way.


But, I guess we both are painting it. Maybe that is a common ground between the two manufacturing methods.And uh it might be interesting to know what the plating is doing.

I will order some xenos for the DI

[joeqsmith]

OK then, just a simple edge of uncoated flange on horn #4.  Stacked coated horn #1 on top of it and used your flashlight suggestion.  Shown with lab lights off and camera pointing right at the joint where the two flanges meet.  No clamps or bolts, just gravity. 

Also note that horn #1 is right off the printer.  No prep work.

[coppercone2]

Hmm nice quality your paint job must be alot better then mine. I bought some 3.6V cells for the depth indicator, just need to buy some mounting arm for the dial indicator now, should be able to get nice measurements with those two.

[coppercone2]

I have a arm, that is 3 sections, 1/4 and 3/8.

I managed to put a post on the granite plate that has a living hinge and a 12-24 screw thread on it.

So I need some way to attach the 3/8 inch shaft to the 12-24 screw and then a dove tail thing to the 1/4 shaft that fits on the digimax 1040 dovetail, which seems to reset to 0.0001 off sometimes, but thats good enough.

So I think I just need 1 swivel thing and one other thing. At least i quantified the problem now.

[coppercone2]

ok I got two starrett snugs that should be able to attach the fowler TI to an arm and then the arm to the stand, I just need to make a adapter that is 12-24 thread to 1/4 inch smooth shaft out of brass that I can stick into the stand, I will braze that together I guess.

been putting off figuring out how to do that for like 4 years lol, those snugs are not cheap

At one point I almost decided to soften and thread the indicator arm so it screws into the 12-24 thread, but I think snugs are the proper way to do it lol

[coppercone2]

also do you know what I should expect from a test indicator, the one I have will return to 0.0001 after I move it, sometimes, but usually to 0.0000.

Is it something I can fix by unscrewing the arm and say cleaning it? I put a drop of silicone oil on there.

[joeqsmith]

All of my general purpose dial indicators have a 0.001 scale.   I have mostly Starrett.  One from Flowler that I keep just for setting up my cam shafts.   I have one of these G models for example but MUCH older...
https://www.starrett.com/metrology/product-detail/711GCSZ

I do have a set of connector gages and test standards.  These are rated for 0.00025.  If I want to measure something tighter, I use one of the profilometers at work. Showing a few bits from a carbon seal from one of my bikes.

[coppercone2]

thats really nice. I figured out how to deal with my setup, the off center drilled 12-24ish hole can easily be enlarged to 1/4 -20 . I threaded a brass rod to 1/4 - 20 on the end so I can stick that in there and put the snugs on it. should have done this 4 years ago

Its fortunate this does not need to be a strong joint, because that thread I managed to make is some real smelly bs, but now the big cast iron ? arm thingy has a brass 1/4 inch rod sticking out of it for dial indicator arm attachment

[joeqsmith]

Interesting question from viewer Wave64.  Sadly they removed it.   Turns out what they really were asking was why the offset short (guessing the short as well) is a dot rather than an arc.  I'm sure most viewer's who follow the channel know that I have been using ideal coefficients but I suspect that in this case, the poster did not understand what that meant.  Here are a couple of articles on the subject that may help other understand why my setups always show dots after cal rather than arcs.   

I removed it, it was a pointless conversation; the above links didn't address my comment.

A 1/4 wave offset short is a 1/4 wave impedance transformer, transforming a short to open, but only on a single frequency. In the waveguide world, the only way you can present a high-Z termination to a VNA is by transforming a short at a single frequency with a 1/4 wave impedance transformer. Waveguide cal algorithms know about this and compensate for this, and when you re-measure your offset short (or as a matter of fact, any "stub") you are supposed to see an arc, as with any 1/4 wave stub. Except, when your calibration algorithm wrongly assumes that an offset short is a 1/4 wave offset short on every frequency - in that case you get the dot when you re-attach it after calibration.

You can fix your calibration algorithm, by de-embedding, or adding transmission line sections (i.e. compensating for phase), depending on how far you are in frequency (and which way) from the 1/4 wave of your offset short.

I hope this helps.

With your comment about it being a pointless discussion and the links I provided not addressing your comment, I was surprised to see you post again.   I'm actually glad you did.  I pondered a day to see if I missed something in your most recent post.  Sorry but it did not help me understand your point.   

As I stated, pretty much all of data I have presented for these low cost VNAs has used the ideal model.  So the SOL and SSL will always converge to a dot.  You understood the two articles and suggest this doesn't address your comment.   We both seem to understand that the open should be an arc but you seem to think it has something to do with the algorithm and not my use of ideal coefficients.   

Start with why you feel I need to fix my calibration algorithm and why you feel that using the ideal model does not explain what I am showing. 

[szoftveres]

Start with why you feel I need to fix my calibration algorithm and why you feel that using the ideal model does not explain what I am showing.

I think that you wrongly assume that the same rules apply to both rectangular waveguide- and e.g. coaxial line calibrations, which is a honest mistake.

In the SMA coax calibration world, it's perfectly normal to ignore the parasitics of your cal standards and use "ideal" coefficients, as you correctly stated. An SMA cal standard, having let's say 1mm of transmission line before the actual termination (50 ohm resistor, open, or short) means an insignificant phase shift at let's say in the sub 5GHz world.
If your center frequency (I'll refer to it as 'f' from now on) is at 2GHz, the added phase shift at 2f caused by the parasitic 1mm transmission line will increase, but will still be negligible.

In the waveguide world however, (as I said above) the only way you can present an infinite impedance (equivalent to and "open" standard in the SMA world) is by transforming a short, with a 1/4 wave impedance transformer, which you achieve with a 1/4 wave offset short.

The phase shift of a 1/4 wave transmission line around f is not just a parasitic - it's predictable, and is extremely abrupt, so much so, that at 2f, your 1/4 wave offset short standard will look like a short again.

And I think here's where you wrongly assume that phase delays around f in a 1/4 wave offset short are just parasitics, and therefore can be ignored.

The phase delay of a section of transmission line that has a length that is 1/4 wave is extremely significant, and by calibrating it out (i.e. assuming it's just parasitics) you essentially take the ability away from your VNA to measure phase meaningfully.

The calibration algorithm for waveguides therefore have to compensate for the phase shifts when using an offset short.

I hope this helps, an I can assure you that your articles were interesting and useful, I just wanted to point out a concern (independent from your articles) with your method of calibration which is worth looking into.

[joeqsmith]

I'm still lost so bear with me.   Lets start very basic.   If we look at the standard definitions for the WR90 calibration kit (X11644A), the difference between 1/4 offset short is the delay.  Note the parasitics are all zero.   If we compare this with Solver's ideal standards we can see the delays are all 0 and it's using a 50 ohm reference.

[joeqsmith]

Attached using the same standards shown during the video you referenced, to calibrate my old Agilent VNA, using only the internal software. *** I would normally run this VNA remote using my software but because the algorithm is what you are questioning, we needed to remove it from the equation.   During calibration I selected the X11644A (X band waveguide) standards and measured S11 only.   After performing the calibration , the offset load was attached and measured.   

Keep in mind that this VNA is limited to 9GHz.  I suspect this is what we both expect.

***
Sorry that the Agilent's print screen makes it difficult to see the data so I took a photo as well to better show the results.

***
Add details.

[joeqsmith]

The PNA can export Touchstone files and using third party tools like AppCad and METAS, we can view this data.   Attached showing the measured offset short. 

Up to this point, I suspect we are both on the same page. 

[joeqsmith]

As I mentioned, my old Agilent is limited to 9GHz so I calibrated the LiteVNA using the same standards with the ideal model over the same range.   A few things to mention.  For the most part, I keep the Lite's IFBW set to 4KHz.  This is the maximum.   This is how I ran it during that video.   The Agilent was set to 35kHz. 

Like before, I just laid the standards on top of the transition.  Basically, I want to replicate what I had shown with the exception of changing the range to 8.5-9GHz so we can compare the results.   

Now, we can see the effects of having the ideal models delay set to 0.   The magnitude is very similar but the phase is not correct.  It's always zero, which when we plot the data on the Smith chart, we see a dot rather than the arc.   

[joeqsmith]

Assuming you have no questions, let's add some delay to the model. 

As I mentioned, I default to the 4kHz IFBW.  The Lite running standalone defaults to 2kHz.  Typically I am willing to take a hit but I have also repeated the calibration using a 1kHz IFBW to show the improvements.   No guide pins and we can see error from my very poor technique (not properly attaching the standard to the transistion).  Still its good enough for what we are looking at. 

***
add details.

[joeqsmith]

How does the offset short measurement compare between the LiteVNA and the old Agilent.  Considering the setup, it's alright.

[joeqsmith]

During the video I had shown the unterminated transition.  It's not a great reference considering all the clutter in the lab right now. 

Also shown is the Short, Offset Short and Load measured with both the Agilent and Lite. 

Hopefully by walking you through the basics of what I had shown during the video, we can now sort out where the confusion is. 

[coppercone2]

do you think its better if I don't have the right calibration standard connectors to
1) remove the adapter that was allowing me to connect to the standard and put a new adapter (substitution)
2) add a extra adapter to connect the DUT

So
1) subtracts something known and replaces it with a unknown
2) adds more unknowns that are well behaved (high quality coaxial adapters), but does not subtract anything that was calibrated for (longer)

I have a hunch that #2 is better, even if your measurement chain is longer

[coppercone2]

I did not get my test indicator adapter yet, but I did manage to do this

I made a bootleg profilometer, IDK how good this is, but I took a comparator stand, and I zero it to 0.000 mm (this one is in metric, the federal digital one) with the horn underneath with the indicator pushing down on the waveguide flange (half way between the apature and the long side edge).

The comparator stands were pulled from garbage and fitted with ebay stuff, but the test I did is I took a old gauge block (possibly east german origin) that is in OK shape, then cleaned it, did a lapping motion a few times on a pink granite block, and then cleaned again with alcohol lint free wipe. I then put it in the middle of the comparator, zero it, then I shift the gauge block around left right, up down, and at 45 degree angles, I did not get any motion past 0.001mm (I think the stand was shifting though, maybe old grease, because it was unrelated to the block motion, it just ticked up). Need to play with /regrease (been 4 years since I greased it) a little maybe. Like it tick up to 0.001mm, but then when I shift the block around, it stay at 0.001mm, it was not following the blocks motion (like sliding around a wedge). Maybe heat related too, kinda need a cold ass zombie to work in mechanical metrology rather then warm human).

I need like a curved gauge block that gets maximally flat so I can mechanically 'chop' my measurement to detect if the stand is shifting/comparator is drifting (digital, old) or if the bottom plate is uneven. Thought it was totally broke at first too, because the measurement head of the indicator was loose, so it was slightly turning/flexing the first time I tried, leading to totally unstable numbers. ! I don't think I should be worrying about 0.001mm though that is 4/10000, probobly can drive myself crazy trying to resolve that accurately


Before measurement I 'lapped' the horn on a known flat steel piece without any abrasive, just to maybe squish unstable blobs.


Then I shifted the horn around and watched the maximum deflection.

I got more deflection on the edges outside of the holes (maybe the indicator spring is flexing it).

Maximum Deflection Results:
near rectangular inner apature
1) silver paint : maximum ~0.1mm
2) nickel paint : maximum ~0.25mm

Outside perimiter including screw hole areas
1) silver paint Maximum : ~0.25 mm
2)nickel paint : maximum : ~0.45 mm

So the nickel paint is quite uneven, and the silver paint is not perfect but better. Seems natural for the paint to be screwed up near a hole, unless you paint then drill its gonna have surface tension related problems there because of an edge formed.


I should print a bare horn and leave a unpainted test object for paint/coating studies when I make things. I am not sure if it was aligned to begin with (the build plate might be misaligned). But still interesting.

I expect the test indicator (lever arm style) on granite block to be much more applicable to this then misusing a comparator.

Maybe I can record a video doing it slowly and then make an actual 2d plot on graph paper with a grid matrix

[xrunner]

Sounds like an edited ChatGPT screed with advertising links for toaster ovens added. 

[joeqsmith]

I thought my new friend szoftveres would have chimed in by now.  If the point they were making was that I shouldn't be so lack in my measurements, I doubt many viewers would disagree.  Then again, many have been upset over my use of a simple torque wrench.    

Here's my last bit of data from yesterday.  To get us closer to what was shown during that last video, I changed the sweep range to 9.8 to 10.02GHz and calibrated the LiteVNA with my extender.   I then measured the Narda reflection standard using the ideal model.  I repeated the measurement with the added delay and loss set to zero (like I have been showing).   In both cases, the IFBW was set to 1kHz.   

While I can't use the old Agilent as a reference, it does provide an idea of the effects between the two models. 

***
Forgot to add the Smith chart.  We can't have that.

***
AppCAD doesn't seem to allow for Touchstone files with different ranges, points...  METAS doesn't offer a Smith chart viewer but it does have a cartesian.   You can see how the PNA (at a lower frequency) compares with the LiteVNA ideal and corrected models.   

[coppercone2]

I would not call it upset over a torque wrench, its just that some people hammer the topic like crazy and then you get scared because you look at the original price of the hardware, and it just seems scary to deviate. But IMO torque is a touchy topic, even with car wheels. Like that old story about union workers dropping their torque wrenches to shut down a line, it makes it seem very important that even with how... loose managers can get with specifications and quality for the bottom line quota, torque can still get to them. Very easy to imagine if the specification was less important, it would be easy for a manager to bypass the 'torque wrench problem' as irrelevant because they are sure its good enough and no one will complain anyway if its 'off by a little'. 

[joeqsmith]

I try and hammer every topic I cover, within reason (until I grow bored).     

I've known softheads that would sabotage their code.  The idea was they would set themselves up to be a hero and save the day when they solved the problems they created.   The end game of course is to make yourself look valuable.  Typical managers are too weak to pick up on it.         

[coppercone2]

I do have a lock in amplifier that seems appropriate for some kind of laser system. Those graphs are cool

[coppercone2]

ah thats nice I got the surface plate with a test indicator working. The silver one looks to be like 0.003 flat across most of the surface on the granite block. I just need to put a drop of glue on the indicator and paint over the crack and I get some pics. Very cool tool.

I wonder if I can measure any RF connectors with that setup. I have the special micrometer for APC-7 connectors, but I wonder if there is other stuff to measure.

The rusty v-blocks I cleaned up show that they are flat to 0.0005 inches

The mini ground jewelry anvil is also flat to like 0.0004 (almost mint).

[joeqsmith]

Still playing with the hybrid T.   

[joeqsmith]

Szoftveres, as I demonstrated in the video and so far with these tests, I have not been securing or properly aligning the waveguides.  Basically, like my use of the ideal model, I saw no reason.   But, I thought I would repeat the test, taking the time to bolt and torque them.   This should at least give you an idea of how the Lite and my algorithm compares with the Agilent PNA.   

The PNA's IFBW was changed from 35kHz to 5kHz.  The number of data points for both VNAs was increase from 201 to 801.  The frequency on both VNA was set between 8.5 and 9.0GHz.


PNA_torque_gravity:  Showing the previous data I tool with the PNA where I laid the Narda reference standard on the transition compared with the proper setup. 

PNAvsLite_OffsetShort:  From your posts, you seem focused on the 1/4 offset short standard I made.   This graph compares that standard being run on my Agilent PNA compared with the Lite using my extender.   As you can see, taking the time to properly set up the measurements has tightened things up.   I'm still not clear about your comments.   I could be doing something wrong as you suggest making bad assumptions and what not but again, keep in mind that the data off the Agilent PNA is their built-in algorithms and coefficients.  That is nothing to do with me.   

PNAvsLite_slidingref:  The Narda sliding reference attached to the Agilent and Lite.   

The LiteVNA does have a bit of noise but as I mentioned, I do have the latest hardware which should improve it somewhat.  Then it's further crippled with my poor man's extender.   Still, keeping in mind everything total (standards, transition, cables, extender, LiteVNA64), maybe $700.  Not bad when you consider the price of a decent VNA.

I have been making changes to the LiteVNAs software as a result of playing with these Waveguides.  I was tired of manually calculating the frequencies depending on the setup and added a few other improvements.   Once I am done playing around with the WGs, I'll upload the latest version. 

[joeqsmith]

Using the same VNA settings with the LiteVNA64 latest 3.1 hardware.  The same firmware was installed.   Plot showing the data normalized to my old Agilent PNA. 

While the one spur still shows up at the same location, the other two large ones have been cleaned up.  With phase being the big concern for Szoftveres, consider it's basically within a degree.   Of course, if I use the ideal model the phase will certainly read 0 as I have shown many times.   

The algorithms that are in question came from various  application notes from HP, Agilent & Keysight.  I'm sure we are all aware how there are mistakes, missing information, and how they evolve.  I could also have made mistakes in my math.   Point being that it should come of no surprise that the LiteVNA behaves much like the Agilent as the algorithms should be very close.

Maybe Brian at Copper Mountain Tech will send us one of their VNAs so we have something to compare the Lite with at higher frequencies....    He's not visited here in some time.  Hope all is well.

[Yannick.R]

If you have another transco transfert switch, you could build a full two port system with your extender.
Your transco switch is rated up to 18GHz, so you could use it in x band.

A first one, allow to switch the
Output of the coupler - 50 ohms terminations or downconverter.
High frequency port 2 - downconverter or 50 ohms terminations

With this one you have S11, S21

A second like you use at lower frequency to switch port 1 port 2
And you will have S22, S12

Then you can play with other calibrations (TRL or LRL) which are nice because you don’t care if the reflect is a dot or a curve. This is not useful. The only information used for solving is that the reflect is on the edge of the smith chart.

[joeqsmith]

If you have another transco transfert switch, you could build a full two port system with your extender.
...
Then you can play with other calibrations (TRL or LRL) which are nice because you don’t care if the reflect is a dot or a curve. This is not useful. The only information used for solving is that the reflect is on the edge of the smith chart.

You could connect a transfer relay directly to your LiteVNA to measure the four S-parameters.  My software supports that today.   You could play at lower frequencies using the NanoVNA and work with Touchstone files along with your favorite math tools.  Once you have the math worked out, maybe include it into one of the open source programs.   I don't believe that the open source programs support driving an external relay but you could certainly add that. 

Depending on your goals, the LiteVNA may work out for you.  Keep in mind that all of these low cost VNAs have their problems.  Agree, they are fun to play with. 

Maybe post what you are doing and the group can try and help you out. 

[Yannick.R]

Yes, I have bought one transfer switch on ebay and I wait the delivery. And I have already installed your software solver32. And I have still to play with an ftdi device and to understand how to pilot the switch with your software and a ftdi. Then I will try to use others calibrations than SOLT.

But I was just suggesting that you could mix your ideas (the use of a switch and the use of an expender) and with your extender and 2 switchs, you can manage to do a full two port x-band vna with the litevna.
You have already a transfert switch that is rated for 18GHz operation according to your manual. If you have another, you have all you need (and cable and time)

[joeqsmith]

Yes, I have bought one transfer switch on ebay and I wait the delivery. And I have already installed your software solver32. And I have still to play with an ftdi device and to understand how to pilot the switch with your software and a ftdi. Then I will try to use others calibrations than SOLT.

But I was just suggesting that you could mix your ideas (the use of a switch and the use of an expender) and with your extender and 2 switchs, you can manage to do a full two port x-band vna with the litevna.
You have already a transfert switch that is rated for 18GHz operation according to your manual. If you have another, you have all you need (and cable and time)

That's a good start, keeping in mind that used parts may no longer meet the manufacture's specs.  It's one reason I suggested you start out at lower frequencies.   Connecting the relay directly as I mentioned, should help simplify your setup.  While you're waiting on your relay,  you may want to download the source for one of the open sourced programs and get the tools setup so you can build it.  Then you can make what ever changes are needed for your experiments.   

Keep us updated on your progress.

***
To automate switching between S11&S21, you may want to look at the old HP33311B relays.

[Yannick.R]

Yes this is better option than playing with a full transfer switch and match: “ The HP33311B has
4 RF ports with one internal 50ohms termination designed for applications requiring a transfer switch or a cross switching element.”

One step after the other but I will keep an eye on this reference.

[joeqsmith]

Yes this is better option than playing with a full transfer switch and match: “ The HP33311B has
4 RF ports with one internal 50ohms termination designed for applications requiring a transfer switch or a cross switching element.”

One step after the other but I will keep an eye on this reference.

Datasheet may be found here:   https://www.testequipmenthq.com/datasheets/Agilent-33311B-Datasheet.pdf

If your only goal is to play with the math though, you may want to simulate everything in software.  This is typically the route I take when adding a new complex feature to my software.   If you're using a low cost VNA,  buying used parts, using poor quality cables and connectors, not using proper assembly techniques and then trying to calibrate it with homemade standards, lots can go wrong.    Sometimes it's better to decouple from the hardware.   

Someone was posting about their attempts to connect a transfer relay + ? to their low cost VNA.  They had repurposed an HP box and it was far more fancy looking than anything I have shown.   Still, the performance was so bad, I used it in a video as an example of what not to do. I tried to get them to simplify their setup to try and help track down their problems but I don't think they ever made it that far.   

The best one I saw was from a person posting how the four S-parameters could be measured using two low cost VNAs connected together with a few Tees (and some software).      Their reason was to avoid the cost of a transfer relay. 

[coppercone2]

I don't think anyone should discourage use of proper test equipment, just realize it is not a substitute for know how and skill. But I don't blame anyone for wanting to work with a chassis, I don't think its some right of passage that you graduate from bare PCB puzzle.

But I will say it again, learning the equipment is hard, and just working with 'boxes' requires alot of learning anyway.

It's your money... money =/= skill. Don't get mad because you think you can spend your way out of a problem.. most people know this by the time they get their first job at a electronics company, that money does not solve problems, but people do. Its less annoying to spend money but no less difficult.

The problem I think is that you need alot of different things, and people are getting upset because they buy a few expensive things, but just don't have enough money to build the test system. It does not magically do more, its just nicer. Its plumbing, programming and electronics all in one.. I hope people realize that its not easy and cool their tempers lol

[joeqsmith]

I don't think anyone should discourage use of proper test equipment, just realize it is not a substitute for know how and skill. But I don't blame anyone for wanting to work with a chassis, I don't think its some right of passage that you graduate from bare PCB puzzle.

For these experiments, outside of using the old Agilent to verify some of my results, the LiteVNA has been fine.

But I will say it again, learning the equipment is hard, and just working with 'boxes' requires alot of learning anyway.

True, my Agilent is a bit cumbersome to drive but IMO they kept it similar enough to their previous VNAs that someone familiar should be able to run it out of the box without a manual (for the basics).   

It's your money... money =/= skill. Don't get mad because you think you can spend your way out of a problem.. most people know this by the time they get their first job at a electronics company, that money does not solve problems, but people do. Its less annoying to spend money but no less difficult.

Making money seems more difficult than hanging onto it.   

I bet a few companies in the US bought their way out of recent supply chain problems.  Hopefully we learned a few lessons.  Doubt it.

The problem I think is that you need alot of different things, and people are getting upset because they buy a few expensive things, but just don't have enough money to build the test system. It does not magically do more, its just nicer. Its plumbing, programming and electronics all in one.. I hope people realize that its not easy and cool their tempers lol

Many I correspond with seem more frustrated than anything.  They typically have a ham license, know everything there is to know about RF and then spend their $50 on a VNA in order to measure VSWR in the most complex way possible.   I wonder how many of the pocket VNAs never made it out of the box because the owner realized that they were going to have to put in some major effort in to use it or that they really didn't have the skills they thought they had and that their ham license is not quite the same as having an education and working in the industry.   

Your last sentence sums up why I enjoy electronics. You will never learn it all or even a small percentage and there are so many different aspects to it.

[Yannick.R]

  I wonder how many of the pocket VNAs never made it out of the box

These are wonderful toy. (And quite good for something to play with). Even not for doing something very useful. Just for the fun.
I am very impressed by what it is possible to do with these very cheap (vs professional equipment) devices.

[joeqsmith]

These are wonderful toy. (And quite good for something to play with). Even not for doing something very useful. Just for the fun.
I am very impressed by what it is possible to do with these very cheap (vs professional equipment) devices.

Can't agree more.    I wonder if they are being used in any of the university classes yet.

[Yannick.R]

Don’t Know in USA. In France, most of the universities are public and money must be spend with very stricts regulations. They can’t buy on aliexpress for example. So never heard of that and probably not. But I’m agree that could be a very good tool for the freshman for the price of a basic multimeter.

[joeqsmith]

Interesting.  Maybe there is a work around where you have the students buy their own.   Seems like that these were made for education.  Beginner damages it (assuming they will) they get a new one.  I'm guessing the access to higher end equipment is limited in the class.

I was on groups.io  (https://groups.io/g/liteVNA/topics) where someone had asked about TRL and WG.  I did post a link to this thread.  With you having a similar interest, you may want to join that group and see if the two of you could work together on it. 

For the experiments I am running, most have been relative measurements.  At most I may normalize the data.  Coppercone2 stirred the pot when they attempted to measure the SWR of their own horn.  (pg7)      I had not planned to make any absolute measurements with the printed horns but plans change.    The three methods I used during the video yielded three different answers.  Not surprised that using a VNA with unknown cheap coaxial standards to cal it, and then we introduce the cheap transition's error.   I'm surprised we got as close to the slotted line as we did once the higher quality transition was used.   

To further reduce the errors, we needed to account for the transition.   And while it was suggested that my algorithms have an error and I was making wrong assumptions,  I'm guessing from the OPs lack of response,  that's been put to rest.  Using the Narda and Muray standards  to verify the the homemade standards, I believe they are enough for these experiments.   

While my old PNA has limited support TRL, it doesn't support waveguides.  They may have offered it with later firmware but I have the most recent version my hardware supports installed.  I have attached a paper that discusses TRL, using WR90 as an example. 

****
I thought I should double check that statement and it does support it.  See attached photos.  Which had I paid attention, I actually showed it previously:
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4801919/#msg4801919
 

[coppercone2]

do you think time domain could be interesting? I have the beadless air line to try that with, its meant for time domain (TDR like?) calibration.

I wonder if that could tell anything about the interface I was so curious about.

I feel like time domain vs bolt torque would be interesting on the horn coupler interface. But I still need to repaint the horn after sealing the chipped waveguide with putty.

[coppercone2]

I bit the bullet and bought 2x wr62 adapters, that are within the cal range of the equipment with favorable connectors. 

Better to just do this right then fool around guessing about the 2ghz above cal range when I see things go south

Just the horns will be less long. I am comfortable to say the horns I made are probobly doing something and might work for something basic but the measurement values are trolls

[Yannick.R]

While my old PNA has limited support TRL, it doesn't support waveguides.  They may have offered it with later firmware but I have the most recent version my hardware supports installed.  I have attached a paper that discusses TRL, using WR90 as an example. 

****
I thought I should double check that statement and it does support it.  See attached photos.  Which had I paid attention, I actually showed it previously:
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4801919/#msg4801919
 

It is not so old I have done some waveguide TRL in 1995 on a HP8510 so before that become Agilent. (On the HP8510 itself, it is not outside using wincal or other software. I have not yet look in detail on  METAS VNA Tools but I have seen you use it and that they say: “ Supported calibration types: One Port, SOLT, GSOLT, QSOLT, Unknown Thru, TRL, LRRM, Juroshek, Reflection Normalization, Transmission Normalization, One Path Two Ports, LHKM, LHKM_TRL_LRL, LHKM_TRM_LRM and Optimization.”. I have not yet have the time to look in detail on what do this software)

I was on groups.io  (https://groups.io/g/liteVNA/topics) where someone had asked about TRL and WG.  I did post a link to this thread.  With you having a similar interest, you may want to join that group and see if the two of you could work together on it. 

Thank you for the link. To be clear on my plan: My plan is first to see if I am able to do nice full two ports measurement. Then if it is ok, I want to play with calibration. The NIST has share a calibration method called multiline also in the 90s or beginning 2000. This is an extension of the TRL method. One of the limit of the TRL method is that the length of the line must represent a phase shift between 20 and 70 degres. (edit mistake 20 and 160 degrees). This doesn’t work well with small or big phase. (For waveguide it is not a problem because the waveguide is mostly used when you have only one mode (so between 2 cut-off frequencies and you can find a line  that will meet the phase criteria). In the case of the NIST, it was for planar lines so with a bigger range of frequencies and they do multiple lengths to cover a wide range of frequencies. So back to the beginning, my plan is to play with that and with planar lines. That I can do line like the ring resonator I have shown before but I will not play soon with waveguide, I have not the skills to fabricate and there are nothing at low cost on eBay from France. I am still in the process of thinking my plan and assembling the bricks. For example, at this point, I do believe that the ham radios community has not seen scikit-rf. (Or I have miss why it is not used). I am interested in what you show and I learn a lot like how to do a transition between coax and waveguide or where is cut the half waveguide (you speak about that when comparing your fabrication and a Narda waveguide (perhaps the sliding load but I have forget, the important information for me was where should be an half guide cut ).

Edit: looking a little bit more on Metas, in release notes

- Agilent PNA Driver improved (support for point average added

- LHKM TRL LRL improved (choosing the eigenvalue for the unknown reflection).

So in your case that is perhaps also an option if the trl is not already in the pna.
And for me I have to work more but perhaps I could use also if I have full two port measurement.

[joeqsmith]

do you think time domain could be interesting? I have the beadless air line to try that with, its meant for time domain (TDR like?) calibration.

I wonder if that could tell anything about the interface I was so curious about.

I feel like time domain vs bolt torque would be interesting on the horn coupler interface. But I still need to repaint the horn after sealing the chipped waveguide with putty.

My software has had limited support for TDR early on.  TDT was a recent change added to display eye diagrams.   I am not sure what you would use it for with this application.  You would be limited to the cutoff frequency of the WG.  Then again, a ham was trying to use my software's TDR mode and they were selecting a very low number of samples (seems like less than 10) to improve the resolution of the distance.  People come up with all sorts of ideas.  They brought it to my attention because my software couldn't run the calculations fast enough to keep up.  Or their PC was too slow....       

I am comfortable to say the horns I made are probobly doing something and might work for something basic but the measurement values are trolls

   I get that.  Basically why I measured the radiation pattern without a horn attached to the transition.  You could see the horn was doing something.   

Hopefully you found a good deal on the transitions.   

[coppercone2]

Well what I was thinking is that it should show me alignment, the time measurement should allow me to see what happens when I move the horn around on the flange while pressing into it, I have a bit of play after I put the bolts. I never saw a waveguide with alignment pins that centers everything super nice.

[joeqsmith]

It is not so old

It does seems like Windows 2000 was yesterday...  At least it has Ethernet and the added bonus of our friends here sorting out the license keys for it. 

My plan is first to see if I am able to do nice full two ports measurement. Then if it is ok, I want to play with calibration.

I take it this is where you want to use my software.  If you decide you want that latest rev, just let me know and I will upload it.  Bugs and all...

I used the PNA to play a bit with TRL at lower frequencies using coax for the standards.  If you're lazy like me, there is a spreadsheet available online you can download from Microwaves101 that has all the calculations.   

https://www.microwaves101.com/download-area#TRLCalc

I saw that Metas supports controlling the PNA and is very extensive but I have only ever used it to display Touchstone files.   It's nice that it can support viewing more files than AppCAD but I wish it supported Smith charts and the ability to select the colors.  Why would anyone think yellow on white is good contrast.   

[joeqsmith]

Well what I was thinking is that it should show me alignment, the time measurement should allow me to see what happens when I move the horn around on the flange while pressing into it, I have a bit of play after I put the bolts. I never saw a waveguide with alignment pins that centers everything super nice.

Guessing your VSWR measurement will be more useful.   *** Attached showing uncal return loss of horn #8 torqued, pushing together by hand and loose.   

That one standard I have is pinned.  See the following link:
https://www.maurymw.com/Precision/Waveguide_Cal_Kits.php

[Yannick.R]

I used the PNA to play a bit with TRL at lower frequencies using coax for the standards.  If you're lazy like me, there is a spreadsheet available online you can download from Microwaves101 that has all the calculations.   

https://www.microwaves101.com/download-area#TRLCalc

Thank you, I would perhaps have try to calculate but with mistake (I have said above 20 and 70 degrees) and from your link:
“The TRL line standard only works well when it is between 20 and 160 degrees electrical length. “

[joeqsmith]

The only way to avoid making mistakes is don't do anything. 

Outside of the last video, anything I have shown with these low cost VNAs has been with the supplied standards with the exception of a sorted load and the ideal model.  Many times I won't take the time to  calibrate or just normalize the data.  The only time I felt a need to deviate from the ideal model was for these last few pages in this thread to compare the algorithms.   

With your plans to not involving WGs, you may want to consider starting up a new thread for your TRL experiments, or toss it into that large software thread.   I can add a new link to the table of contents for you. 

[joeqsmith]

Horn #8 attached to extender, calibrated from 8-11GHz.  Showing the impulse response with band pass enabled.   The horn is pointed up.  Note disturbance at 1.6 meters.  Maybe there is something else of interest besides measuring the height to my office ceiling.   

[Yannick.R]

Perhaps measuring the humidity of something. (More water, more loss)
Example fresh wood, old wood.

[coppercone2]

Did you have just the wave guide coupler measurement parameters anywhere? (open waveguide coupler without antenna)

I ask because I think I did the calibration right, and it seems that the open waveguide is a surprisingly good radiator. and that the antenna does not do that much when put on top of the coupler! Like mating the antenna with the coupler... does not do anything too dramatic with that SWR plot, and makes it worse in some places... but I will have good data in a few weeks when I get the stuff thats gonna be within the calibration band

Like the best improvement was only maybe 0.4 SWR, but it was already like damn close to 1 without an antenna. I guess they radiate pretty good?

I need to get some known good components to connect to the VNA to verify the cal. I think I have some low pass filter and stuff, but I wish I had a arbitrary standard of some kind. Actually I think I have a 18GHz wideband load (the cal kit is low band + line0, let me put that on

[coppercone2]

btw i think its cool that you made a radar

[joeqsmith]

Perhaps measuring the humidity of something. (More water, more loss)
Example fresh wood, old wood.

Why would you suggest TDR would be a better choice than return loss for this?  Seems like band pass impulse isn't a good fit.   

[joeqsmith]

Did you have just the wave guide coupler measurement parameters anywhere? (open waveguide coupler without antenna)

I ask because I think I did the calibration right, and it seems that the open waveguide is a surprisingly good radiator. and that the antenna does not do that much when put on top of the coupler! Like mating the antenna with the coupler... does not do anything too dramatic with that SWR plot, and makes it worse in some places... but I will have good data in a few weeks when I get the stuff thats gonna be within the calibration band

Like the best improvement was only maybe 0.4 SWR, but it was already like damn close to 1 without an antenna. I guess they radiate pretty good?

I need to get some known good components to connect to the VNA to verify the cal. I think I have some low pass filter and stuff, but I wish I had a arbitrary standard of some kind. Actually I think I have a 18GHz wideband load (the cal kit is low band + line0, let me put that on

I think in that video where I look at the radiation patterns, that's what really tells the story.   Good VSWR doesn't insure a good radiator.   That Narda terminator for example has a maximum VSWR of 1.015.  It's sealed up and isn't going to made a good antenna.  Same for the coaxial loads I test with.   

SWR plots: Yellow is with nothing attached to the transition and nothing but the ceiling in front of it.   Violet is the Narda terminator.  Red is horn #8.   

Radiation plots,  Blue is with horn #8 attached and red is with nothing attached to the terminator transition. 

Agree, its good to have a few known devices to validate your setup. 
***
BTW, I did try a few tests where I used the home made standards to calibrate using one of the low end LRL transitions from the training kits.   Like bad coax, calibration can't fix a bad waveguide.    

[Yannick.R]

I have missed the point that it was restricted to TDR. So it was a more general answer to what to do with my horn.
https://pubs.geoscienceworld.org/vzj/article-abstract/2/4/500/91573/Near-Surface-Soil-Water-Content-Measurements-Using

[joeqsmith]

Original posts begin here:
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4815032/#msg4815032

I can't access the papers you linked but it appears most of this work is done at very low frequencies which may help explain their use of time domain.  There was a member here that I understand was professionally involved with similar efforts.   They have not posted in some time.   He brought us the phrase "ego pimping" when referring to myself, which we still use.

[coppercone2]

I tried a radar on mine, able to get a ~600ps difference by waving a roll of copper above the antenna, but it seems to loose the response pretty quick, I guess you need power and a better setup for distance. More then like a half a foot and there is no well defined signal. I wonder how much of that is caused by the antenna being right up against the analyzer, its probobly reflecting off there and swamping the instrument

At least all the reading I tried to do on radar receiver methodology long ago has some relevance now. Scary equations were totally useless to me up until now. I see I am missing some sort of pulse feature though for the domain, I guess in that mode of operation it would be more like a real radar I think. Needs two sweepers.

[0culus]

I tried a radar on mine, able to get a ~600ps difference by waving a roll of copper above the antenna, but it seems to loose the response pretty quick, I guess you need power and a better setup for distance. More then like a half a foot and there is no well defined signal. I wonder how much of that is caused by the antenna being right up against the analyzer, its probobly reflecting off there and swamping the instrument

At least all the reading I tried to do on radar receiver methodology long ago has some relevance now. Scary equations were totally useless to me up until now. I see I am missing some sort of pulse feature though for the domain, I guess in that mode of operation it would be more like a real radar I think. Needs two sweepers.

You need a *LOT* of peak power to make a pulse modulated radar worthwhile. In the meantime, if you search around on ePay enough you can score a suitable TWT amp for reasonable money. 

[joeqsmith]

.. able to get a ~600ps difference by waving a roll of copper above the antenna, but it seems to loose the response pretty quick, I guess you need power and a better setup for distance. More then like a half a foot and there is no well defined signal. I wonder how much of that is caused by the antenna being right up against the analyzer, its probobly reflecting off there and swamping the instrument
...

I would expect with your setup being capable of measuring beyond 20GHz, you can resolve far below 600ps.  Attached showing a phase trimmer attached to the LiteVNA, adjusting roughly even steps.  X-axis is in ns.  Time between cursors is roughly 50ps.   Video link showing a similar experiment with the V2Plus4.   There was that ham who explained to me that they could lower the number of samples to increase the time resolution.   < 10 samples should do it.      There are lots of good papers from reputable sources on the internet.

https://youtu.be/XaYBpPCo1qk?t=4244

[coppercone2]

Oh you can do that, I mean beyond 600 ps from the little horn right up on a coupler 2 inches from the rack it does not resolve a reflection from more then say 900ps, and its dodgy from 600 ps onward. 300 is like the initial peak from the reflection of the coupler or just passive reflections I guess, if its 3cm per 100ps, it should be a little less then 9cm for that setup. I won't be finding any b2, but its hitting the top strut of the rack also and the other shelves a little I think, I need to actually lead it out to a clear range. Time to fix the tripod , think I need a helicoil to fix the threaded bit

But I do imagine that these little 3d printed antenna would be more then enough for a supermarket door opening circuit from those tests, and maybe even for collision detection on cars. Lightweight drone nav system maybe, if you can get the rest of the circuit, maybe 1:64 scale model AWACS or cyberdyne systems rotorcraft w/fully functioning radar

[joeqsmith]

Got it.   That reflection from the ceiling was roughly 1.6 meters with an output level around -8 to -10dBm ish.   The half power beam width for that horn is 18 degrees.    If I tried that same test without the horn, I doubt we would see anything but noise. 

[coppercone2]

I wonder if you can make a coupler that attaches directly to a PCB, i.e. a square of copper with a pin that you fit the wave guide over, as simple as something as a copper wire that is soldered upright and filed to the correct dimension, so you just screw the PCB to a wave guide

so its like a monopole antenna that couples to the wave guide. Coupler is kind of like that already I think, it just has a coaxial connector on it.

it seems that naturally it would go together well with 3d printing and it might be the key to making some antenna arrays for phase array projects

[joeqsmith]

I suggest you make a simple sketch to better show what you envision and post it.

[coppercone2]

Hmm Ok but for the mean time I tried the 12-18 GHZ coupler. As you said, there is very little radarability from a coupler without a antenna. I think the higher frequency one might have been a smidge better though when by itself


At least the WR62 is big so painting the antenna apature should be easier.

[coppercone2]

piece of shit 3d printer is doing something funky, I think its the set screws or the mechanism for holding the build plate for the resin tank.
Guess this is gonna get delayed for a while.  :'(

1 moving axis, of course its too complicated to work. Haha, with my luck, I wonder what kind of shenanigans would go down if I had the filament type. God damn machine

[coppercone2]

I failed the print around 5 times. I got 1 horn that came out after a bunch of adjustments. Then the screw for the build plate was not tigthened and I got a deformed horn. The fep film broke down, the alignment broke down (thanks set screws), a failed stick on, etc

I think I shall paint it, after the current print is done, I will have 3 wr62 horns, one of which is... ripley. Might be interesting to see what the paramters are of the horn that clearly survived some shockwave pattern from a missile  Maybe I can sand it down and fix it with some putty instead of just throwing it away, kind of a shame.


3d printing is like Alien 4, before you get your clone right you end up with a whole room full of .. problems. I am starting to feel like Mason Wren...

[coppercone2]

Bought a new build plate for 3d printer, since the old one keeps loosening even though its torqued real hard. I got it used and cheap even years ago so I guess that maybe it was a bit dodgy to begin with. I don't want to experiment with trying to fix a ball joint, its probobly quite difficult. Set screw + ball joint =

Will be painting two slightly deformed horns after dinner, will get some pictures

[coppercone2]

well primer made this go so much better. For the first one I was not sure if primer would help on the 3d print, since its plastic and stuff, but it helped big time, but the mg chemicals spray paint can is still trash that sprays little globs of paint

[coppercone2]

oh yeah the results are much more clear with the lower frequency, on just the SWR indiana jones test I get 0.4 SWR lower across the board (the launcher is 1.5 and with antenna it goes to 1.1). With the higher frequency it was not so clear. It might be a cal issue of course, that stuff is so touchy.

[coppercone2]

These are the WR62 horns. I want to try to make a RF gasket for them by mixing 2 part silicone with silver powder. Quite the ordeal to make these lol. I forgot to thicken up the walls, and the print bed was messed up, so I had to file them a little but they do work (warped and a offset near the end). I have a new bed coming for future work. Still better I think then what I saw in some old air force training videos on youtube, they look like they were playing stick ball with those wave guide parts.

For gaskets, what do you think the best procedure is for making them? I thought maybe to just make the mold, pour silver powder in there, level it off with a playing card or whatever after tapping on it, then pour silicone on top so it seeps in and fills the gaps, fully cure, trim with a fresh razor blade and demold. Anything more then that I think would be hard, you would need to dry ice or maybe liquid nitrogen lap it I think, if you wanted to sand the silicone nice.. or make a two piece mold I guess, but that is alot of work

[joeqsmith]

Warp is an understatement and the file marks are clearly visible.  You may be better off with sand paper.   Why waste the expensive coating on the outside?   Because I processes so many horns together, some have over spray but it wasn't my intent.   

I haven't considered using gaskets for the connection points.  I've shown you how flat the printed parts are and ran your flashlight test. Hardly a concern for me.  With some of the experiments I ran, I have been using the choked flanges with O-rings to get them gas tight.  Lots of playing around but haven't anything to show for it yet.   

Did you run some sweeps to get an idea how well they radiate, or are you only looking at the VSWR?   If you are, post some photos of your setup.   

[coppercone2]

Its two effects

1) Its too thin and it warped, possibly when I ultrasonic cleaned them in that lab soap powder.
2) the print bed got loosened during the print and it started offsetting when the pull force got too high (near the end of the print the horn grips the plastic better), so each time it got set down on the last 20% of the build, it was like, rotated slightly in a random direction (5 hours into build), so it started looking like the damaged pyramids of egypt with big 'steps'

I torqued the bed alignment screws hard as I could, to the point of damaging the set screws, but it still loosen up. New print bed should come in soon.

Idk if its bad tolerances on the machining, damage, cheap screws or what, but I see that mechanism has a spring pop out of it when you open it up for trouble shooting so F that


They need a collet on the ball joint of the print bed like the 'smiths vise", instead of set screws. I saw someone build on on youtube for a special grinding setup, but of course that joint probobly costs more then a top end 3d printer.

So to clarify some of those marks that go side ways not lenght wise are missing material because the printer offset, but there are some file marks. It needed very aggressive cleanup.

[coppercone2]

As for more photos I am waiting on some wave guide parts so I can do a better test

[coppercone2]

The the summary on this page for wave guide joints is good if you need a refresher like me about the different joint types and what practical effect your choice of joints has.

https://globalinvacom.com/products/flanges-flat-groove-and-choke

[joeqsmith]

As for more photos I am waiting on some wave guide parts so I can do a better test

How are you measuring the VSWR and radiation pattern today?  Are you using a VNA?  If so, which?   

I saw that RS 40GHz VNA on ebay for $5k a couple of weeks ago.  Looked like the drive was dead but it booted up and physically appeared in good condition.  Didn't look abused.    I checked used prices for working ones and seems they were running around 40k.   

[coppercone2]

its the 8510C that has 20GHz gen and 18GHz reflectometer, and the 7mm cal kit with the sliding load and air line, months to fix the system and restore it (the sweeper had the leaked alkaline and I ended up combining two sweepers and redoing a silk screen on the mother board to make one functioning one)

But the cool thing is I have 2 couplers that go WR62 to APC7, so I can try to calibrate out wave guide now by putting the coupler at the end of the setup. But it will take a while to fly that from all over the world

I think I saw that VNA too or something close, but its down right scary to work on those machines IMO. I  think they make you bald with too much exposure to the open chassis with PCB removed (from stress). I cut down when I started lookin in the mirror dealing with that in my spare time. I tried to clean up all the connectors, grease everything, replace suspect parts, and reseat all the components I could find (like screw down caps and even the chassis shield elements that slide around and crap like that), to make sure that the contacts are all good.

It had demons too, it was crashing for some reason, but I dunno it seems to have stabilized some what.


I am gonna find out if you can swab the barrel of  a wave guide by putting never dull wadding on a stick.Don't think I want to be paying for that rhodium plating


seriously my stomach churns thinking about what you might run into that R&S unit lol.. serenity now, potentially add another $50 for antacids

[joeqsmith]

   I've had to repair most of my equipment and maintain it.  I don't get too worried anymore.     I was thinking how much time I would waste just trying to get a service manual and software for it.  Then I am guessing license keys would need to be regenerated.  Get that all done then figure out how to align it.   Maybe a nightmare or a very good deal.   

Do you run the 8510C standalone or with a PC?   What calibration does it support?

[coppercone2]

It runs stand alone right now, I have a computer in the other room with the card and I was meaning to make a hole in the wall to connect to it.

I assume you mean this menu?

[coppercone2]

and this is the standards that I can use

[coppercone2]

and this is the ones I can't use yet because I need the different reflectometer

[joeqsmith]

So for waveguides, does it support the offset short, shims and such?   For the cal standards, does it have a database for the ones HP sold?   If so, I wonder if you load up one of the waveguide kits, how it compares.   Just curious.   

[coppercone2]

not sure yet need to do more research. there is this thing but its too expensive I assume that you just put those things on and do the same cal routine

https://www.ebay.co.uk/itm/382213470112

[coppercone2]

lmfao I remembered  I left some corn in the little steam oven last week and forgot to eat it because of that manufacturer. at least its not smelly

[coppercone2]

you would be looking at the 11644A calibration kits from HP for waveguide cal with the 8510C. At least thats the higher frequency one. The lower frequency one must exist too.

I don't think the disk ever changes the menu options that you see, it just loads values for them. Unless it makes custom standards, which you can add, then I don't know. That may be a whole other feature I am not familiar with. I think I heard about capacitance standards and some weird stuff, not sure how it interfaces programming wise.

[coppercone2]

and for the paint, you should see how much paint dripped on the floor because of the shitty spray can. This was NOT a neat process. It sprays about as good as putting water in your hand and flinging it at something


But I wanted it double sided just incase some paint flaked off inside or something. And if I do metal plate them, it will look much cooler, I could just put gloss or epoxy on the outside

[joeqsmith]

Nice kit.  Looks like they still offer it.   Check the very last page of their catalog: 
https://www.atecorp.com/atecorp/media/pdfs/data-sheets/CMT-Waveguide_Specs.pdf

Yes, what I have shown is basically my poor man's clone of the X11644A with a few other bits.  Do you have to load the cal kit from disk, or is it built into the system?  Can you change the coefficients and save them back to disk? 

Looks like the hams use 10.368 GHz and 24.048 GHz.  You seem to be trying to experiment in the middle of it but with posts about WR42  are you planning to get more accessories for the 8510 to use it at the 24GHz?

I plan to stay around 10GHz as that seems to be a sweet spot for parts availability and price.  To use the LiteVNA with my extender to measure S11 at this frequency, it really needs a new amplifier, coupler and adapters.  I tied a test the other day with some really bottom end adapters and was amazed just how poor their insertion loss was.   You get what you pay for.    That old coupler is spec'ed to 8.3GHz but I have shown data up to 10GHz even with the connectors and low frequency amplifier.           

[joeqsmith]

For the paint, maybe you could get a cheap airbrush and just cut the old cans open and pour out the contents into a sealed container.   OEM may offer some suggestions on thinners and setup.   

[coppercone2]

I don't think its the right kind for that unless you reformulate it. It seems to like bubble and stuff when you spray it out, I had a few spots that were not painting and what I did is sprayed the paint into a little tray and swirled it around a bunch so it thickens up and then you have a few seconds to work with it before it cakes up, in a viscous form, that has low mobility so it wont migrate off the spots that the primer fell off after sanding due to surface tension or whatever the hell is happening there.

Maybe if you can spray it out, dry it out, then add regular paint thinner, it might work? I think like there is butane or something that is dissolved in the whatever to make a unusually volatile solvent. Maybe its just me but it does not appear to behave the same as other paints. I think it dries much quicker. I dunno I guess the SDS does not say anything weird maybe I can drip just a bit of acetone in there to adjust it after it stands out for a little bit and try it.

Maybe its the same, I guess I never tried to paint brush spray paint because its not worth while since there is no silver in it. But the liquid seems weird in the tray lol

[joeqsmith]

They offer thinners for manual spray applications.  Have a look:
https://mgchemicals.com/category/conductive-paint/conductive-paint-thinners/

They call out AR, which I assume is what you used.  Wouldn't hurt to ask them.   

All the test horns were PLA.  I had no problems with the primer adhering to the plastic.  All of them were primed except for one.    If you wanted to try to manually spray them, you may want to ask if there is a better coating for your particular plastics.   

[coppercone2]

Hmm the thinner is IPA based but the paint is acetone based .I guess it works with everything and they just want acetone in the spray one because it evaporates faster?

[coppercone2]

I got a wave guide tuner to try to see what will happen to VSWR with it. should have the setup in like 1.5 months 

i got alot of captains, pilots and drivers im depending on for this setup

[joeqsmith]

I got a wave guide tuner to try to see what will happen to VSWR with it. should have the setup in like 1.5 months 

i got alot of captains, pilots and drivers im depending on for this setup

In route then along with other goodies?   

I have a few slotted line stub tuners that came with that box of junk.   One of the experiments they had the students perform was to measure the VSWR and tune it with an open end.    Showing my results, yellow is open ended transition, red with the tuner attached and trimmed.   So we can certainly reduce the VSWR.    You may remember that very first section of home made WG and my pork and bean cans had stubs on them.   You could drill a few holes and add a few set screws.   Then you don't have to wait. 

[joeqsmith]

Here is one of the workbooks I had found on-line.     

https://tecnoedu.com/Download/56-200.pdf

[coppercone2]

Yeah, but I also am debating if I should get some flex wave guide. I feel like the circuit is going to be hard to put together without any flexible things. Not sure what I want to make, I see there is a few different Ku band things like the x band spectrometer thing that guy was building here, maybe, but in general, it seems that I would need some spare wave guide tube and flanges to braze on to make a custom circuit that connects to the VNA with all wave guide. I wonder if anyone even does that

Do you know the difference between E&H Tuners and the sliding tuners ? Hard to find info on them. Is it a choice based on power level? I think it would be nice to use as many wave guide parts as possible, its interesting to me, there is always some cost saving substitution involved normally

I can try that experiment if I get a few more things. Debating between some options and styles for some of the parts.

[coppercone2]

you need quite a bit more hardware for that PDF then what I have. But I think if I get some of the basics then its a good way to make a setup like that and experiment with self manufactured parts.

And of course I need to build a case because this is going to get out of hand

[coppercone2]

btw for wave guides, I wonder how 3d printed wave guide filters would look like. The Iris type filter looks very printable, just glue a lid on top with conductive epoxy after printing. or the dip coat. Being able to crank those suckers out might justify buying a gallon of silver paint. I think maybe like you can take a 1mL sample of the paint can too, to weigh it, if you plan on keeping it for a long time, so you can add the correct amount of lost solvent to maintain the mix.

I think x or even Ku band might work, clearly, based on how I see the horn functioning on the VNA.

I gotta say I feel a bit.. redundant printing just wave guide conductor sections, the horn is marginally interesting but its still quite simple, but making arbitrary filters in a few hours is damn interesting.

I am just saying it does not feel very special. But band pass filters seems next level.... that seems like a capability not being a cheap skate, and its really new grounds, not reinventing a 'wire'.... their highly non standard parts, not common elements.

https://www.sciencedirect.com/science/article/abs/pii/S1350449513001667



I feel like the doc lol, its not quite uranium but its the first time in my life I felt like I could really use a big quantity of a precious resource to do something scientific.......

[joeqsmith]

The SignalPath video where I showed his attempt of a 3D printed horn, he also shows a 3D printed filter.   I've seen other articles where people have 3D printed them with decent results.  For example: 

https://www.egr.msu.edu/eceshop/testingfacility/connex/papers/3DPrintedMetalizedPlasticWaveguidesforMicrowaveComponents-1.pdf

[joeqsmith]

Do you know the difference between E&H Tuners and the sliding tuners ? Hard to find info on them. Is it a choice based on power level?

See attached.  Full catalog may be found here:
http://hparchive.com/Catalogs/HP-Catalog-1960.pdf

I've not yet had a need for flexible line.   I would like to replace the amplifier, cheap adapters, coupler and filter on my frequency converter.   

[coppercone2]

I got my tuners, wow, I am glad that objects in the ebay pictures are smaller then they appear.... (got the 870A)


Looks like the right choice, its a power level thing mostly. I won't be doing that kind of research.

[coppercone2]

I wonder what kind of stuff connected to wave guide has such attorcious VSWR (20) that needs to be corrected. Very specific radiation pattern and polarity stuff?

[joeqsmith]

Maybe attach a shorting plate and then try to correct it. 

[coppercone2]

I think it must be something for apatures maybe for small samples that need testing at a specific wave length or something?

Like you would think that if the VSWR is greater then single digits it would for sure require a redesign. I see the old VHF bridge from HP went to 2000 ohms for <1GHz. Information on such reflective objects being used practically is low I think

and this previously resulted in people discussing chokes, so I guess it might some how be useful for that. Something with isolation etc

you kind of covered it here, with ohms instead of VSWR
https://www.eevblog.com/forum/rf-microwave/high-resistances-at-rf/



But the question in my mind is still: is there some kind of absurd antenna that has extremely bad VSWR but does something otherwise unique. Say extremely narrow beam width or something. That kind of makes me think of those quantum antenna / emitters. Alternatively maybe a kind of like a laser line scanner type deal, but for microwaves. Like horn antenna vs squegee. borg scanner beam 

[joeqsmith]

Antenna wise, I can't think of anything.  If it's that far out of wack, I doubt it will radiate.  Why add a tuner when you could fix the problem? 

I've ran many experiments that had I measured VSWR, it would be well over 20 but I can't think of a case where I wanted to compensate for it. 
I was playing with that hybrid T and could see if you were attempting to use it to measure something unknown, you could use the tuner to balance the bridge and then use it's micrometer as a readout. 

[coppercone2]

oh boy I took the tuner apart to grease it and it does not have alignment stops. Centering the pin is gonna be a pITA

I thought there is no way there would not be a guide pin or something to setup the rails. But the rails turned out to be glued plastic and there is no guide pins or shoulder stops or whatever.


Probobly need to play with gauge blocks or something to parallel them and fix the thing in the middle


I guess it does not need to be precise but I seriously imagined some much much much more advnaced mechanical hardware to do this! its like cheap! mine would be like a grinding machine x y table!


dare I say : proxxon quality 


tldr : its made with wind shield wipers that need to align a precise mechanism! stomach ache!@

For some reason this wave guide stuff reminds me of startrek deep space nine, the episode where star fleet decided to loot the abandoned station to replace wave guide or whatever the hell is in those conduit runs. Wish I could find a old HP ware house of these 'guide rails' (maybe you can use mazda wind shield wiper blades or something). One of them is missing some chunks of rubber-plastic or whatever. Quite ratty. Thought it was cardasian but its fernegi

[coppercone2]

do you know how the depth stop on a SWR meter tuner should be set? One of them actually has the micrometer digging a groove into the wave guide, I guess you put a shim?

*getting delirious from trying to align this thing

[coppercone2]

never mind, its just a grime mark, the micrometer was properly set, but enough crud accumulated on the wave guide to make it look like it got scratched. phew

[coppercone2]

as usual, after working all day eager to get the job done trusting the seller it turns out their X band and they don't fit the fucking antenna ! I have been working on that shit for like 2 weeks and I still can't tell the difference

into the rabbit hole i go

I say there is about a 30% probability of receiving the correct size wave guide part through resale.

The solution is to get both bands. I am sure I will end up in either the THz region or receive a pallet of WR2300 eventually............................................................... its just square right, you just need it to prop up a shelf. total fucking worm hole, you don't know what dimension you will pop out in.

[joeqsmith]

as usual, after working all day eager to get the job done trusting the seller it turns out their X band and they don't fit the fucking antenna !
...

I thought all the old HP waveguides were prepended with the band.  So X870A is for the X band, using WR90.  Normally if the part is no longer marked, I will just ask the person to measure it.  I have had to do that with some of the salvage yards.   

You could make adapters to go from what ever band you are working with to the X and back.  Then use the tuner to correct for all the errors you added.   

[joeqsmith]

I should have wrote, read that manual I linked as the letter designation was not standard at that time. 

https://www.microwaves101.com/encyclopedias/frequency-letter-bands

[joeqsmith]

Photos were taken from my 1950s MIT RADAR book. 

[coppercone2]

Oh no the picture was diff then what arrived and it arrived in diff quantity . Mad fail . But at least I did not get tucker Carlson coffee mugs or something

[joeqsmith]

There are a few P870A as well as the P880A there.   All fairly inexpensive.   

If you ordered 1 and received 10, I wouldn't bitch too much even if they were the wrong ones.  Resell for a profit and buy the right ones.   

https://www.ebay.com/itm/310953362258?epid=1918800173&hash=item486643c352:g:B3oAAMXQ2UVQ5dvq&amdata=enc%3AAQAIAAAAwGJbZk1BI3Dl6MFo7%2B0VB8WjwzEk2iNbYRieNQ9yjQoz%2FtTEh3ebEN8b%2FVFOW6gBLuuD8rfoZjqxmSKJYgA3SvR7IazzBKH1wKmt9PK9FxspGo82cUd5tAAMut8tJWUNhnFRg5FJF5IVhTRmM%2BdZCuCIGOcxR9cKxRAK5XVdip%2BwymtFRhpDYnuKrmRyZ1fs5F7DH%2BoGot0T7lNGBIRVHlOknJUztYpndKJXwqLztqGQDcxcUlanh9Vu4jO3o%2BA0gQ%3D%3D%7Ctkp%3ABk9SR7Tbwv38YQ

https://www.ebay.com/itm/223942490007?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20201210111314%26meid%3Df49cf473079c47f6a528705deedb3386%26pid%3D101195%26rk%3D4%26rkt%3D12%26sd%3D310953362258%26itm%3D223942490007%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv11WebTrimmedV3MskuWithLambda85KnnRecallV1V4V6ItemNrtInQueryAndCassiniVisualRankerAndBertRecall%26brand%3DHP&_trksid=p2047675.c101195.m1851&amdata=cksum%3A223942490007f49cf473079c47f6a528705deedb3386%7Cenc%3AAQAIAAABUA2rugFlOq3qu1cLac%252F%252Fk6Vp0Oa0HaJIqoXKeIiOR%252BTUgsSvHaeyPxKYu6UqHqq7GaGyKVqHQnjeiiXcQpMGw2t3aB%252BssGfjtIWOBj8wExc7oYYP7xGMyQCrHDyDaSaWjB1CueI3A94n0yxXX5dx5gAAXolEeNO8u8k6D92DWA4yCIJxgBKBicSQlyh7C5d2KjB%252FeXfcretsgT8RvDI%252BujKBKhSsmiRMLh3piQ8nDAtf%252BsYCcCXEZQsU4konEYAyoS533y8TH71w262HFz%252BLZATtnSVOyFEHVql9Jfw4UyDn%252FKkPRXS%252BhkjlkbgPQQXkH81DAwODDtXK8nN3w9pIydpkH5ha%252Bj3fDvLtvNtBr4G1DeIwiiYf4VRtZKRnSPoZxXZCEZtA297Xn%252Be9APZGc0y%252B3HWAkGncxNGTqCSwPbJyoyeb9o2ny0PuK5yAUJ1tLw%253D%253D%7Campid%3APL_CLK%7Cclp%3A2047675&epid=14039252709

[coppercone2]

Lol yeah, I wanna get into this band also I guess, just you gotta be in it long haul, no quick anything when it operates like this.

What I want to do is develop a bio implant that makes a caliper or ruler shoot out from your knuckles like wolverine

Maybe I will attach a caliper with a magnet on it to the refrigerator or something, or even a ruler. Maybe a ruler tatoo

[joeqsmith]

I replaced the 8GHz amplifier and the adapters.  There's a slight improvement in performance.  Still using that coupler way outside it's spec'ed range.

[coppercone2]

What do you think is the integrity for those wave guide loads?

I assume its like a big carbon composition resistor? I have SERIOUS doubts about old ones being 'good' if its carbon comp based.

Are calibration wave guide loads... carbon composition?! I am allergic to purchasing carbon composition unless I can replace it with something. I usually put metal oxide in everything I have the time for.

[joeqsmith]

They are mechanical so unless they were mishandled or left outside, I would expect them to be fine.   In my case, I used matched load to measure the mismatched load and it seems fine. 
Considering these parts most likely were from the 60's, they have held up well and are good enough for my home experiments. 

Of course, you could purchase new standards.   

[coppercone2]

I thought wave guide loads consisted of a dissipator?

is that thing in the left of the picture you posted a 50 ohm dummy load (5W?) Narda 3something

I thought it was like this thing
https://testparts.com/waveline-wr90-waveguide-termination-dummy-load-x-band/

In a youtube video I think I heard something about carbon, but I am not sure what form.

[joeqsmith]

I thought wave guide loads consisted of a dissipator?

is that thing in the left of the picture you posted a 50 ohm dummy load (5W?) Narda 3something

I thought it was like this thing
https://testparts.com/waveline-wr90-waveguide-termination-dummy-load-x-band/

In a youtube video I think I heard something about carbon, but I am not sure what form.

Oh!!! Ok, I take it you didn't watch my video on calibration and waveguides are new to you.   First, there is no 50ohms.   It's closer to 500.   Like a coaxial load, the waveguide load just needs to absorb the signal.     If you want some idea how they are made, Mario had posted a link in the third post.      That Narda part I show is rated for 1W average.   I would imagine if you put 100W into it, it would change.   I am banking on the cross check I performed with the Agilent to give me some idea they are still all fine. 

Still aging of lossy ferrite or other absorbing materials is interesting.  Not just for the terminator but for attenuators, circulators, isolators...   I bet there have been some very good studies done on this.  I just spent the last several minutes with Google and no luck.   If you decide to contact the Maury Microwave or other standards manufacture, post what you find out here. 

[coppercone2]

well I see some deals on old stuff but I also wonder if they use the same material a a carbon comp resistor for their loads (forgot about the 50 ohm, that info is on first page of the wave guide book) and it is basically horribly drifted now.

it might not even be sealed up nicely like a resistor is, possibly pulled from wet wave guide (the stuff will condense water pretty good IMO). Recpie for disaster with carbon comp I would not be surprised to find 6000 ohms change

Some say silicon carbide though that should be as good as a rock.

Hehe if I am disappointed by a damaged rubber dove tail in this tuner, how will I feel when I find a carbon comp ingot inside of that thing. 

that kind of 'standard' can send you up a tree when you realize you retuned your experiments to run at 2000 ohms impedance or something

But when I hear ferrite and carbon, both can drift really bad. 20% inductor drift with age is not unheard of either for the right types, and carbon comp can be whatever IMO.

i.e. whats in this thing 🤨
https://www.ebay.com/itm/294824491288

when I think about it like that and see how it looks it reminds me of a old suit case, those never work out well. Baking might help but I got some serious suspicions.

[joeqsmith]

The dimensions of the WG should be fine, as long as it was taken care of.  Look at  the precision mismatch load I show in that last video.  Granted, remove that absorbing material and the reflection will increase but to get that mismatch, they change the dimensions of the WG.   The fixed precision Narda terminator uses a conical element that extends the length of the part.  The Narda mismatch sliding load uses several wedges.   

[coppercone2]

I wonder how hard it would be to replace the suceptor in there if it failed. I don't know enough about quality but I did have that experiment that I did trying to make the ceramic silver PCB, if you arrange silicon carbide stones like stone henge in a microwave in fire brick they will glow real bright.

I would if its as simple as getting the correct sized silicon carbide stone and gluing it in a wave guide. (the vitrified ones or whatever).

I still need to redo that experiment, I got actual glass powder extracted from glaze and I need to just mix it with silver in the correct proportion (quartz powder does not sinter well, you need like glass). If it needs ferrite in there then its not easy and you might as well buy a new load.

[joeqsmith]

That is a J910A, where I assume you would want the P910A.  Even then, these are not a reference standard. Maybe you would want the P914A.  Their standard fixed terminator was the 816 but it looks like they only offered this for the X-band.   

I don't know if HP ever published the materials they used, or even if they made these parts.   You could try a patent search.   

Realization of Wide Band Waveguide Terminations at Ku-Band
Pramendra Kumar Verma1*, Raj Kumar
https://ijamt.com/index.php/ijamt/article/download/43/22

[joeqsmith]

Just to give you some idea how the terminators I have compare.   The Narda 300C has a max VSWR of 1.015   So the return loss is  -20Log10(vswr-1/vswr+1) or 42.6dB.    The Narda 410-15 has a VSWR of 1.353 or a return loss of 16.5dB.

I used the extender (new amp and adapters, same coupler)  to sweep from 9 - 12GHz using a IFBW of 1kHz.   I calibrated using my home made standards as before but for those that don't like the error cause by the ideal model I  have used the Agilent model.   This was also taken with the latest revision of the LiteVNA hardware.

Attached plot showing all three standards and also the short.   Also shown are the two LRL507 terminators that were part of the university training kits.    These are just slightly better than the Narda offset load.    Performance suffers above 11GHz but again that coupler is spec'ed to 8.3GHz and its isolation is poor. 

My point is you may not want to buy just any old terminator, if you plan to use it as a reference.

[joeqsmith]

Member Virtualparticles video on VNA accuracy and directivity. 

[coppercone2]

I cleaned a dirty mylar foil type rotary attenuator.

If you are interested, the mylar is fine, and the glue is also fine, after 20 seconds in the ultrasonic for the sensitive assembly. There was alot of crud in there and it looks good now after a DI rinse. The other parts I cleaned between 1 minute to 5 minutes. I rinsed with alcohol spray and after it dries up I will relube the bearings and other stuff with silicone oil or wd40 specialist grease or teflon grease. Drip the fluid silicone grease into the stacked rotating stuff, and wd40 grease in the bearings so it can be cleaned out if I make it/see this thing again in a few decades, and silicone teflon grease on the worm because its easy to clean with a brush.

Looks like they used q-dope or something to hold the mylar sheets in the circular wave guide. Same stuff as inductor wires in other RF equipment that I see 'tacked' on the chassis.

It looked kinda clean but the ultrasonic pot is dirrtttyyyy, and the bearing grease gelatinized a bit.

This one looks like boba fetts ship

and never - dull polishing wadding did a wonderful job on the highly tarnished wave guide flange for the twisted segment.

[coppercone2]

damn, chipped a small amount of mica (0.5mm triangle) (i think its silvered mica, I thought it was mylar initial) from the corner of one of those plates inside the wave guide. I wonder how well that will work  just could not get some scrap of something out of there 

I will wait for the stand to come in before I do testing so I don't damage anything more.

[coppercone2]

Hooking this up is not easy, this will take a while. That attenuator is just a weird object. I need to make some kind of shelf thing that is compatible with lab jacks, make some adapter for the attenuator out of wood so it sits on the lab jack, etc

I need to invest and solve a few problems before I end up in shit creek and have to post a thread about how to fix a snapped APC-7 connector and panel beating a TR set

the rack setup I had was fine for coaxial, but for wave guide its a whole different ball game.

I almost did it, and then I remembered executive decision. And the intro sequence to aliens colonial marines. And I decided to hold off. The worst shit in the world seems to start from shoddy umbilical practices. 


it looks like the damn mounting nuts on my rack mount structures is blocking the shelf from being put on, I need to make some kind of offset hook thing so I can clamp it on a place where there is a shelf nut sticking out.

[joeqsmith]

I'm surprised you have not 3D printed custom stands by now.   

[coppercone2]

the stand is not the problem, the shelf is.

I was confident I could put a rack half shelf on the front of the unit because I forgot that the nuts were in the way. The plan was to hang the rack shelf off the holes in the front of the rack so it can be adjusted to any height, but I am not getting a good face to face connection on the flats because there is shelf nuts in the way, so basically I need like a extender. with hooks on it. It needs to be like a comb that fits between the nuts and makes a true connection

it would look like a lower case pi shape foot thing

And if I make more stands, its SUPER tempting to copy the HP stand that i Need to take pictures of. It looks like a cone. It has enough space in there to put a commercial collet in there for a small adjustable post. Then you just put different forks on top for different wave guides with a universal stand.



I got one, can't find more, but I HIGHLY recommend that design. Its just a shaft that gets tightened into a cone, and the shaft has a hole on top that you tighten a fork into. Easy to make out of brass but my 3d printer is too small to print the base in one piece. I want to do it with some collets I found once that you thread into place, instead of a side screw, but even so that one is easy enough to make with a hole saw, some metal plate aluminum, drill bits and brass rod for the center post, and you can even put it on a turned wood base no problem.


But the uh, attenuator, I think it was pulled from the side wall of a B52 or something, very irregular mount.

[coppercone2]

I made some plasma cutter mods to get the shelf to install nicely (I also will advertise the NOGA brand sheet deburring tools (looks like a rapier handle) as useful here, but unfortunately the ceramic 'non ferrous' one is not good enough to debur the nasty flash from the plasma cut, so you need to use the hard metal (carbide) one then the ceramic one and then light sanding, but its nice)....

but I am still scared to just put the wave guide there resting on a offset because its too hard to tell WTF is going on with the racks. Maybe if they were really sturdy rackss, but these I can tell are bowing etc...

So I bought a few sections of flex wr62. Because I was thinking I need to glue alignment flats and maybe a compass on the parts and start doing some weird shit, and something is gonna break on a assumption of something being true if I do that.

I made this after having a good look at what a transmission reflection test set on a rack mount really is, geometrically

[joeqsmith]

The cast pie shaped ones I have I'm sure would hold a 100+ lbs ea.   I think I have maybe five or six of them.  I like that they have a low profile.  Keeps the WG bits very stable.   

Post a photo of your vintage attenuator. 

[coppercone2]

this is what I managed to cobble together that I am scared to try to plug into the analyzer without a flex relief

[joeqsmith]

WOW!!!  That thing is huge.   Thanks for posting.   

It does sort of look like your photo on the right.

[joeqsmith]

Did you take photos when it was apart? 

Looks like there are both WR62 and WR90 versions of it on ebay.
https://www.ebay.com/itm/295049543429
https://www.ebay.com/itm/294103708332

So your intending to use this as part of a bridge?  How does it fit in to the picture?  You have the 8510.  Is there something you can't directly measure with it?

[coppercone2]

I dunno I just read the lists for various projects and it usually mentions an attenuator or two, really big work in progress. I was just gonna calibrate it when its 0db and see what the wave forms look like when I turn it, and just see how it behaves on 'thru'.

I can take a picture inside after I break it down later but its just a worm gear and a big gear that has the center tube in the middle that is attached to two bearings. I don't want to take it apart until I decouple it, tired.

It has 3 glass? metalized plates inside, shaped like machinist fish tails that nest into each other. All in a line at 0 db and the middle is orthogonal at 55db

I wanted like the basic wave guide kits to do anything even if I can measure it with better equipment, with whatever I will eventually do (Honestly I don't have a solid plan, just scrounging the stuff up till some kind of critical mass occurs). I find usually when there is a.. complete set of parts around, just getting to do something is more spontaneous. I don't expect miracles, just mild amusement and interest.

[joeqsmith]

... just scrounging the stuff up till some kind of critical mass occurs).

  

[coppercone2]

Solid state attenuators are also interesting. Not sure where the state of the art is, but for someone with a bigger budget then me that wants to be more modern, with out worm gears and mechanical computers,

I need to get the picture of the 'computer' there too, its like a helix cut into the indexed aluminum cylinder.

http://dbmcorp.com/broadband-solid-state-attenuators/
https://www.ebay.com/itm/144877536115 (don't think they go that far, think its a passive accessory, but its still a nice idea for a wave guide stand or something)

But that might have cylon problems

I feel like it might be capable of doing AM voice communication on MW with only attenuation. That would be a interesting experiment, similar to that old 'water cooled carbon microphone' that was supposedly used to modulate that big transmitter.

[joeqsmith]

This was my last purchase.  It's a 40mm section of WR90 with UG-39/U flanges.  She has some heft and feels like brass.   I shaved off some coating and metal on the backside and no plating.   Shown next to aluminum with a drop of bleach on each.  It has a few marks I need to lap out but overall in very good condition.   Looks like current scrap price is $25.84 per oz.  My balance is not able to measure it so at least 4 oz. 

[coppercone2]

Try never dull on it, it made my old wave guide look great.

I need a very short section to test it on with the granite plate  to see how much material is being lost through that process though. Its like wet cotton in a can, you tear off a bit and buff it gently. I feel alot better using it them messing with liquid polish + rag.

I think its a mechano-chemical polishing process that uses very fine abrasive and also chemicals. I think they use similar for wafer polishing.. it might be a more advanced polishing process that does less damage. It leaves a wet clear residue, not a milky one, so its something different then just mixing brasso and cotton. I think the abrasive remains stuck in the cotton. If you try to wring it out, you just get clear liquid coming off it, there is no 'mud'.  And no strong odor, brasso smells super pungent in comparison.

I had some silver plated stuff, I found that the only thing that quickly wore through the plating to show copper was the brown (coarse) silicon carbide rubber cups. The green (fine) one had a high level of control, you could definitely stop before you wore through the tarnished plating, with a feather touch. I don't like using the buffs BTW, too messy and hard to deal with the polishing wax sticks, cotton cleaning, etc... the rubber ones are much better if you can afford them.

https://www.amazon.com/Nevr-Dull-NEVER-DULL-POLISH/dp/B00097CRY6

[joeqsmith]

The plan is to resurface the flanges.   I did remove a fair bit of material and repeated the bleach test and once again, black.  Appears there is no plating. 

Using my larger balance, I measured the part at 170 grams.  Density of Silver is 10.49 g/cm^3.   I used water to measure the volume and measured roughly 20cc.  So roughly 210 grams.  A fair bit of error but does seem to point towards some sort of silver alloy.    Would need to run it on a mass spec to see what it actually is. 

6oz at $25.68 or about $150.   Paid about $20 for this one but want it for a sample holder not for scrap.   But that video I showed where the ham was talking about where all the WG materials have gone.  It makes perfect sense that salvage yards would want to maximize profits and scrap makes perfect sense.    I'm glad the part was saved. 

[coppercone2]

they should just stick to scrapping cars, should be plenty with EV roll out, then waste time on esoteric scientific equipment

 I suspect alot of 'road trash' will not be in service anymore since there will be reasonable automobiles for sale

[coppercone2]

how do you plan on holding a tall object up on a lapping plate?

Like, the part is difficult to hold on to without tilting. I often wondered if you could make a 'collar' that fits the object in the middle so you have a big thing to grip for the lapping motion. The taller it is, the more ridiculous it is. I also imagined some kind of stabilizer spider looking thing to go on really big objects, with like loose dampers or something that keep it mostly aligned (like the mechanism of a hone kind of).


I want like those hands from the old andromeda strain movie for this.
https://en.wikipedia.org/wiki/Remote_manipulator

Like imagine trying to do a 2 foot long brass one.

You think if I managed to pick up a MSM-8 at a government auction I could hand lap big stuff with it? Amusing to think about what would happen if we actually got good haptic feedback powered exoskeleton armor suits one day, what kind of ridiculous will result. Like a big ass space marine resurfacing a tractor engine on some crap made out of old sewer grates and 'frontier guard' gear being mis used to make giant gauge blocks and such for sale on the black market. rust belt of the milky way. You think the emperor knows what we are doing with his shit?

[joeqsmith]

how do you plan on holding a tall object up on a lapping plate?

Like, the part is difficult to hold on to without tilting.

Most likely, I will do it by hand.  WR90 is fairly large and not a problem to hold onto. 

[coppercone2]

I feel like it’s really uncomfortable to get a rythem going with tall objects in figure 8

[joeqsmith]

Standards were done by hand as well.  We are not talking about a lot of material. 

[coppercone2]

I imagine the guy doing the 4 inch gauge blocks in the kit was NOT a happy camper compared to the guy doing 1/4 inch blocks

[joeqsmith]

I imagine the guy doing the 4 inch gauge blocks in the kit was NOT a happy camper compared to the guy doing 1/4 inch blocks

I would assume gauge blocks are not made by hand and the only unhappy people are when we go to pay for them.

[coppercone2]

I don't really know what standards were made that way, lets just say my fingers are not happy with this, that just comes down to bone anatomy or whatever. I felt cramps after experiments to try to flatten things out like that which are tall

When I 'lapped' a gauge block on a granite plate (it would not wring?, but after a few figure 8's it wrung), the 4 inch one was MOST unpleasant. I think this is OK because its not gonna keep happening. Just super awkward to grip and hold true while in motion. I know they have the stone for it from starrett, I just wanted to see if the kits worth anything at all, apparently so. That experiance made me think any wave guide more then say 2 inches tall would be a pain.

Ima just say it reminds me of standing strait in small boat, but with my fingers.

[joeqsmith]

You started out with concerns on tilt but now it seems flatness.   For the waveguide standards, they need both or at least the offset load would need the flanges surface to be parallel to the shorting face.  In my case the mill is good enough for that followed with a quick lap.   

The standard were all well under 2"  This section is 40mm but I have finished some of the other parts by hand as well that were taller.  Holding it by the flange is no problem for me. 

[coppercone2]

I probobly confuse the terms because I don't work with precision mechanical technologies very much and use whatever intuition I have to try to save time and energy because these projects are mega broad in scope and it never feels like you have enough time and it has not yet resulted in a mega fail.

[coppercone2]

BTW, did you use collared bolts with your wave guide?

I noticed when there is a complex wave guide structure, I have no idea if its aligned properly, I can't look inside, and all the manufacturers are different so trusting the flange to act as a guide maybe is not the best idea, some of them seem a bit off.

I mean the bolt that has a slightly wider non threaded part above the threaded part that should theoretically align the holes like pins would. It must be better.

It might be called a pin bolt.

[joeqsmith]

Shoulder bolts.  I have a used them for some setups but for much of what I have done, I used paper clips.  When I measure the antennas, I did not use shoulder bolts.   So far, the most critical measurements I made were to compare my software's calibration algorithms.     

[coppercone2]

It might be interesting to have super aligned when I am playing with the flex wave guide soon. I got a longer one too so I can see what it does while I bend it and its testing.

And even if you can trust the flange, you can't trust the paint difference between the manufacturers.

I will look for some shoulder bolts.

[joeqsmith]

0.1585 - 0.1590 measured on shoulder
0.160 - 0.161  measured on threads

So at least for the ones I have, the thread's OD is more than the shoulders.  Yours?

[coppercone2]

Oh I don't have any shoulder bolts of that size, I want to buy them. Its just not something I ever desired before

I got some gigantic ones from something in one of the parts boxes, but it was probobly from furniture or something.

That is hardware which is very difficult to stock in a useful way, because how could you know what shoulder depth you desire? I guess if you stack washers or put a pipe it could be kinda modular but its really pretty specific IMO

I asked someone IRL and he said that it will always be that way because they are rolled from steel not cut. SO it probobly means that a custom part is necessary. They don't have a way to actually make the shoulder thicker then the thread if its rolled unless you do some really crazy shit

[coppercone2]

But it is possible to make from brass DIY I think, by brazing three things together, and using a cup washer. So long the pin is the correct dimension it will align everything, then even if you have a crappy offset miniature bolt in the middle, because you drilled it on a drill by eye with a wobbly vise.

So I can get the correct dimension brass tube, cut it to lengh to make a stub, drill it, put a smaller brass bolt in it that sticks out a bit, put it on a brass disk, solder it together, then braze two different ID washers together to make a washer that has a ciruclar flange thing, and it should compress everything. I think I can line up a bunch of these stacks and braze them all on one go on a fire brick if I can't find the correct part. I would probobly make it a square bolt because its easy to cut.


Since there is 4 of them, it should hold

[joeqsmith]

Maybe use your precision cal standards to perform a calibration, then rotate the parts from one extreme to the other and measure the difference.   Try it with thin, thick and no paint. 

***
Maybe forget the cal, and just try it.

[coppercone2]

Got it, so long you ream the wave guide hole by a little bit

my dyslexia kicks in on mcmaster

The precision shoulder bolts are available with a shoulder wider then the thread.
https://www.mcmaster.com/products/shoulder-bolts/shoulder-diameter~5-32/


The major diameter is 6-32 or 5-40 = 0.1250 or 0.138, the shoulder diameter is 0.156

The hole is like 0.145. If I ream them, then the shoulder screw should work. The shoulder height is not super critical because I can put a washer so long its not too short.

I will try it when I get my flex guide before I buy the bolts and start modding things. Irregular wave guide would piss off the 3rd hand market. At least I know I can solve it though. Calmness

[coppercone2]

The other thing I can do is like a assembly aid, to buy pins that fit precisely, put in 4 pins, clamp it, remove the pins 1 by 1 and replace with bolts.

Probably should do that, its what people normally do to align metal thats not armor.  If it was on a battle ship that was going to take a beating it might be a problem but yeah

i need some time off lol, not thinking clearly here

[joeqsmith]

For instance, generic flexible waveguides tend to have poorer RF performance, i.e., insertion loss and VSWR, even though they may solve routing, misalignment and vibration challenges. Nonetheless, if a flexible waveguide is made with the appropriate sized sections for a specific frequency, the insertion loss and VSWR can nearly match a solid waveguide over a very narrow bandwidth.

https://www.microwavejournal.com/articles/print/26932-rf-waveguide-tips-and-facts-you-cant-learn-in-school

Paper on alignment.

https://ntrs.nasa.gov/api/citations/19970023425/downloads/19970023425.pdf

[coppercone2]

Do you know if there is like a flex rating for wave guide?

I ordered a 1 inch, 3 inch and 8 inch piece. The 8 inch piece came in today and its kinda stiff. It will do for the VNA front panel I think, but the 1 inch piece if its the same stiffness would just be too stiff.

And yeah my idea is very close to a bootleg version of that paper! wow

[coppercone2]

For cleaning the flex guide, I used neverdull on the end faces and then ultasonic it in the lab soap powder for 8 min and then rinsed and used clean water for another 8 minutes.

The alconox gets brass much better looking. I did not really want to submerge it but it was looking a bit dirty inside, I hope I did not tarnish the edge of the spiral wrap. I imagine a gentle flexing after bake out will reform whatever metal to metal connector was there. Usually things look electrically better after the ultrasonic cleaner...I assume its like corrosion growing on a knife edge or something that gets pushed out

Now I will bake it for a hour at 75C and try it out

Actually I have no idea if its a metal to metal seal or if its just a solid piece of metal. I figured its made like armored power cable out of ribbons. But I never saw a video.. research time I don't think its built like a vacuum capacitor?

https://www.microwaves101.com/encyclopedias/flexible-waveguide

[coppercone2]

some fucking bnc cable went out behind the 8510c and yeah going back there lol behind that machine infested alien bull, at least nothing shocked me, thought the sweeper broke

but it looks like it all works. I just used the saved cal routine that just the apc-7 to wr62 to wr62 to apc7 to cal, and plugged the wave guide thing in front of it with a short circuit on the end of the attenuator

and it goes from bad VSWR to nice VSWR at max, so it works I guess. I need to play with it more but my friday was ruined because of I think a BNC cable, this is with refleciton measurement, I just did whatever to get away from the basement with pictures to post . I left it connected so I can try to play with doing a cal with the wave guide network attached tommorow

WHen I took the attenuator apart I was not sure what angle is max attenuation and what is minimum, in line is minimum (I figured this out by solving the formula near the diagram with the 4th power cosine or whatever, glad I got the 'polarity' correct. I thought 10% chance some mis understanding would occur that I put it backwards.

[joeqsmith]

Looks like the shelf is up to handling all that weight!   

One of the experiments the students performed was to connect a short to an attenuator and then measure the VSWR with different settings.  Similar to what you appear to be showing.  The students had to run this at a fixed frequency of 10.5GHz and use a slotted line to measure it.  None of this fancy VNA stuff.   

Attached showing using LiteVNA to conduct this experiment.   I used my standards to calibrate at the kit's transition then bolted on the attenuator and short.  You can see how poorly these parts behave but good enough to demonstrate the change in return loss. 

[coppercone2]

is that switch reused or did you find a part number for it?

Its the same design that I Hate from the HP amplifier to push the attenuator button  inside the chassis, but it looks really cool on a wave guide

I guess its just a custom mod for a wafer switch? For this application making the detents nonlinear would be interesting too, so you can have a mechanical switch that follows a geometric pattern of detents

[joeqsmith]

is that switch reused or did you find a part number for it?

Its the same design that I Hate from the HP amplifier to push the attenuator button  inside the chassis, but it looks really cool on a wave guide

I guess its just a custom mod for a wafer switch? For this application making the detents nonlinear would be interesting too, so you can have a mechanical switch that follows a geometric pattern of detents

There's no switch.   Only the transition, attenuator and shorting plate.  Guessing you are confused thinking that slotted  flap-type attenuator is a switch with detents.   Maybe read the following on attenuators.   

https://electronics-club.com/waveguide-attenuator/     

Shown sweeping from 10.9 to 11GHz, adjusting the attenuator in half marks from 0-24dB.   The extender's directional coupler limits running it any higher.   

[joeqsmith]

I think if you wanted to use one of these poor quality attenuators, with say a stepper motor.  Characterize it over the entire range.  You still can't correct for it.  It would be better to start with a good attenuator.  These were are a good choice for training kits,  low cost and durable.   

[coppercone2]

One of the old HP amplifiers has a detent wafer switch on it that has a wedge shaped piece of aluminum attached to it. When you turn it, the detent goes into the correct position for the metal flap to press down on a micro switch. The mechanism is super fragile because its not made with the right interface.

For the rotary resitive card attenuator it would be possible to use that switch to make a stepped attenuator. I mean the one that operates like a guilotine not the one that I have.

I thought thats exactly how you made the attenuator there.

I don't know if those types of attenuators are used outside of physics class diagrams though. I think this one
https://www.torontosurplus.com/hp-j375a-agilent-j375a-variable-flap-attenuator-0-20-db.html

I thought that you 3d printed one and used a old wafer switch to adjust the flap angle

[coppercone2]

And for the shelf for the rack the way I did it is for most of my shelves I have 4 post full size adjusting shelves, but I had some single instrument deep shelves.


So if you put the coupling nuts with the little metal holder behind the front of the rack, you can bolt a 1/2 size shelf onto the front of the rack and it holds pretty good with just two screws. But you need to trim the back lip of the shelf, which I did with a plasma cutter. That way you can adjust your shelf in rack spacing holes.

But you might still run into nuts on the front, in that case you need to make a offset modification, which I did not do yet, I just got lucky with the shelf being able to be positioned where I wanted it to be. The idea with that would be that the shelf could fit over any thing sticking on the front of the rack.

I also wanted some quick release mechanism, maybe with springs, so you don't need a screw driver to reposition it. Or just hooks.If you put it on hooks, which I thought to bend out of some very stainless steel I have that is very tough (after plasma cutting and heat bending), it would just need a offset 'heel' to rest it over any rack shelf bolts so you can put it on any free hole. Like ladder hooks. The shape is easy, it would be this, I just need to work out the distances so nothing lands on a possible bolt

And you can possibly just cut it from square/rectangular tubing slices if you have the right size, not sure if any standard form would fit easily.

[joeqsmith]

"I thought thats exactly how you made the attenuator there."

All of the WG parts were made by LRL.   

My shelves are just PCB that I cut and soldered.  The weight of the equipment keeps them in place.   I used to just slide sheets under the equipment but it flexes and parts were always rolling off.   Mad two with a lip which solved that.  Sill, it would never support the weight I expect you are putting on them.   

[coppercone2]

Ohhh that paint on the switch part looks very much like the silver conductive paint. I thought that was 3d printed

[joeqsmith]

Ohhh that paint on the switch part looks very much like the silver conductive paint. I thought that was 3d printed

And while you may not want to come out and say it, it certainly looks crude enough to be home made. 

I'm not sure what they plated these with.  Maybe nickle. 

[coppercone2]

Ahh I replaced that screw that fell out of the vise jaws like 5 years ago and gave them a nice ultrasonic clean and all the stuff, so I can bend metal without it slipping wrong. I will try to cut some stainless steel strips for the hooks and see if I can find some form to bend it on. Having that shelf removable is gonna be nice, I think I can make it so it hangs on the side of the rack when not in use, almost walked into the attenuator

[coppercone2]

I got the 1 inch long WR62 flex. I think this is the one that is a solid piece without the wraps.

Its not very flexible. If you don't know what to buy, get the long ones. The short ones like this is OK for another misaligned wave guide, but if you want connector strain relief, its gotta be pretty damn close to nominal.

If your setup is really bad, I would recommend 1 foot or longer flex guide. Even the 8 inch one does not flex that much, its very stiff stuff.

[joeqsmith]

Lapped the flanges of the short section.  Next step is to make a new shorting plate for it.  Thumbscrews are to make it easier to insert the samples.   

[coppercone2]

nice reminded me to buy some thumb screws for the pasta maker because I stopped using it since it draws in dough into the gears and I need to unscrew it every time

I wonder if I can make that on my proxxon mf70. I think I can, with telurium copper and a new atlas 3 fluke non ferrous end mill. How thick are they? I made stuff out of electrical copper even on it, but the problem is the cutter is so small, it really should have a fly cutter, it would be mad hard to get it actually flat. I would need a new XY table though, it runs stiff, last time I made something some what big I was cursing at that stupid knob. The casting or whatever it is was cracked and I fixed it with super glue lol. The surface finish looks super cool though, if made with tiny end mill.

[joeqsmith]

My shorting plate is about 6mm thick.   Most likely will use the same material.   

[coppercone2]

You gave me an idea, I find it very annoying to put the nuts on the wave guide one at a time.

I wonder how hard it would be to make some kind of like thing to put over the wave guide to position the nuts. I like the idea of a 3d printed bracket shape that has magnets in it, so you can load 4 nuts into holes, have them held in place magnetically, so you can get it started and there is no chance of spilling it etc, then just lift it off. Like a nut starter or whatever specific for the wave guide size.

or ideally two tools, one with 2 pins, and 2 nut holders, and the other with 2 opposite nut holders. That way you can keep it balanced on pins while you put the first bolts on, then remove, and put the other plate on once  its already kinda held together. No bullshit. And the pins need quick release slide collets on them too, with like a spring, like the thing you have on sports bags to keep the nylon cord tightened. That I think would be like really good. I need a extrusion printer though because I know the resin parts will be too weak for this. It would be actually aligned on pins by the time you tighten the first two nuts, perfect, not some edge clamp that you guess with (according to the paper its a very small effect, but still, its like a purpose built spanner or something, nice to have even if you can do it with pliers). 

[joeqsmith]

Paperclips may be the fastest.   The threaded flange may be an option. 

[coppercone2]

What do calibration constants look for the plates you made?


I guess if its accurately machined, its standard numbers that are available?

Obviously I don't know what to do without the data disk.

[joeqsmith]

What do calibration constants look for the plates you made?

I guess if its accurately machined, its standard numbers that are available?

Obviously I don't know what to do without the data disk.

They are based on the Agilent standards.  Which includes the new shim. 

https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4801919/#msg4801919
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4786121/#msg4786121
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4797443/#msg4797443

[joeqsmith]

Playing around with the frequency meter from LRL.   It's basically a circular cavity with a micrometer.  I shorted one side and plotted S11, uncalibrated  (yellow). Then using that old HP adjustable short to make another cavity, I was attempting to use copper foil tape to make an iris for it (red).   Lots of attempts.  Q seems a bit better.   

[coppercone2]

hmm speaking of metal iris, I never had strong feeling for a optical iris at having good continuity between the sections, but this one might (I saw it on adam savages channel for makers)
https://us.makerscabinet.com/products/iris

Fascinating idea, optimally I think it would be made of berylium copper sheet. I imagine the safe way to do it would be to make a stamping die for cutting the segments.

Or it might just be possible to get a standard manufacturer to assemble one without anodizing, or just send you the raw parts for alodine coating and assembly. I think it would need a extra lip for copper fingers to be really good, maybe.

If you stack a bunch of thick iris with offset cams I imagine you can approximate a conical taper with a very big mechanism to make a universal adapter for circular waveguide tubes

[coppercone2]

When you did your multi antenna tests, did you experiment with near and far field?

https://www.emc-directory.com/calculators/far-field-distance-calculator-for-horn-antennas

But its a bit bizarre because you get negative numbers for the low end.

need to be precise, about the frequency, it figures out cutoff I guess for the wave guide.

But for 12.5Ghz, with a 45cm2 aperture area, it says 16.5 meters far field. For 18Ghz on the same antenna, I get 1.1 meters.  And it goes down the smaller you make the aperture. So I am thinking that short horns might be useful for something too. Need to see what the parametric program does to flare angle. I think its adjusted for length automatically by an equation. But I think it might be interesting to print some shorter ones, if you are close to the VNA and stuff. I think you mentioned it in a video but if anyone is trying this...

θ=2*tan^−1(d/2*L)
              l = axial length

              d = aperture dimension

              θ = flare angle

that 16 meter figure is pretty huge, I was not expecting it, you really need to design antennas for experiments based on your work area.... very incorrect assumption. I guess it makes sense, its like a big air capacitor. But still I think I had the PCB near field probe thing in my head... so just plugging in those antennas with elbows infront of the VNA would be very near field if I did it.

[joeqsmith]

Say the horn is 80mm X 80mm, with a freq of 10G.   Wavelength would be 0.0288782 meters.   2D^2/wavelength is 0.426962 meters.   

Using the calculator you linked, with an aperture of 80^2 or 6400mm  gives us  385.04186074  meters.    Using an aperture of 80mm it gives us 0.06016279 meters. 

If you like on-line calculators, if I try:
https://www.everythingrf.com/rf-calculators/antenna-near-field-distance-calculator

and use the same settings, it show a far field of 0.42696198 meters.   

Could be a user problem.  Double check my math but it looks like the calculator you chose may have a problem. 

[joeqsmith]

When you did your multi antenna tests, did you experiment with near and far field?

Outside of showing that wire polarizer and swapping the E&M planes,  no.   To compare the radiation patterns, I was only interested in the far field and used the same setup each time.  The only thing changed was the antenna.  Well until some idiot decided not to use a wrist strap because after all, the horns are grounded....       Even so, repairing the amplifier appeared to have very little effect on the measurements.   

The problem as I mentioned is that to test the antennas from the papers I provided, they test them at much further distances.  I went over that in that video and talked about not being able to run them at the normal distance.   But because I was only interested in a relative comparison, I wasn't too concerned.   

[coppercone2]

hmm how did you damage the amp from ESD? The horn is connected to the chassis ground, the center pin should be floating deep in the wave guide?

Did you accidentally touch the center pin some how? I am reluctant to use a wrist strap too because it seems... well grounded and protected.

I need to attach a ground point on the rack I think so I can plug in right infront of where I am working. But being chained sucks

[joeqsmith]

Not the center pin directly.   Cable makes a decent capacitor.  ESD is pretty high frequency.  Bingo bango.   

Was just being stupid.   I tend to slack off with these low cost VNAs.  Did you check their math?  Sure seems wrong.

[coppercone2]

Hmm I never thought of the high frequency coupling thing from coaxial cable. Maybe I am lucky because its a concrete damp basement.

The protector for high frequencies are ridiculously expenisve.

I need to check the math still but not soon because the weather is nice today

[coppercone2]

I did think of a sanity check before digging out equations from god knows where:

for a parabolic horn fed antenna, the reflector is positioned in the far field region right? that might bound the problem, I never saw a antenna with a 50 foot feed

I am gonna guess before I do something else that they mean D = largest dimension that all the web pages say and the area picture on the site is a mistake and its not a mistake that they wrote cm instead of cm^2


so just confusing legend, I think, because I spent 15 minutes and I don't see anything obvious about using the area of the aperture as the calculator implies . so its probobly a... reduced equation. Wonder what the original looked like. I wish to see it. Need text book I guess.  I guess the formula  has like a scaling coefficent that is say 1/lesservalue^2 as a multiplier that results in 0.1% error or whatever, so they just got rid of it because its basically useless?


here we go, water cool your brain

[joeqsmith]

No need to chase down formulas or simplify anything as the link you provided for the on-line calculator you used provided the equations.  Just some basic math was all.  As for the area vs a sidewall, I had tried that and posted the results in my example.

Nothing on that site, or any of the testing I did uses a parabolic reflector.   Using no math and just thinking of a common sat dish, 2.4GHz, dish about 3' dia, horn about 1' away.   Total shoot from the hip.   At the 10+GHz you are talking about, I have no idea where that 15' is coming from.    Even the old sat dishes that were 8' or so dia, horn's focal point was only a few feet away.   

[coppercone2]

the how to web pages with formulas but not calculators say that the major diameter or longest diameter is used for the equation, not the area. But the calc I found shows area. maybe tonight I can try spread sheet comparison

[joeqsmith]

If you run the numbers for the table provided, they calculated the area from the longest surface.   They show a WR90 horn with a width of 2.66" or 67.56mm.  Close to the 80mm example I used.  At 8.2GHz, their table shows 0.25 meters.   Calculating it by hand, I get 0.24972.   

https://www.atmmicrowave.com/waveguide/horn-antenna-standard-gain-wide-band/

[coppercone2]

That makes sense. Maybe I will take a crack at the equation from that video if its appropriate, been meaning to learn some of the harder math behind these things, I put enough effort into trying to make them. not the worst math I run into anyway

[joeqsmith]

Replacing the copper foil tape with my homemade iris.  Still pretty crude but better than the tape.   Data again with VNA uncaled.  Iris1, sweeping from 8.5-11G.  Notch is really narrow around 9.1G.   As we zoom in you can clearly see the cavity resonate.     

[joeqsmith]

Looking at the drift.     

[coppercone2]

that made me remember that I found a optical iris once, they use greasy o-rings to adjust a square aperture, its a very smooth mechanism that is simple.. just friction on damping grease.. it basically drags a plate in a groove in a indiana jones way, like if you were pulling a long spaghetti over a news paper.. octopus style..so you just rotate a wheel and it rotates a o-ring that tends to drag the plate in one direction and its sticky enough to stay in place.


What is the drift from anyway? DO you think its something to do with mechanical state or mainly the instrument and temperature? Hard to imagine the screw being responsible given how stable a micrometer is.


what is the sweep duration? That would be interesting to know the time constants associated with stabilization.

[joeqsmith]

Reminds me of some idiot telling me to use some gold something or other contact gunk on my RF connectors.  Just try it, they would say.      Guessing a ham.

Drift wise, hard to say without running more tests.  The PDRO is tied to the GPS.  The LiteVNA has no reference.  Most of the bits are copper or brass with a fairly high TC.   Currently the houses temperature is fairly stable.  No A/C or furnace.   Then there is the whole paper clip, me moving things around on the desk....   

Easy enough to get rid of the paper clips and use the stands.  If I normalize the data, we can get a better view of the drift in the notch area.   Shown with the first half hour of warmup.    Now that it has warmed up,  I'll let it run for a longer time and use 100 avgs to clean up the noise.   Sun is coming up and the house will start to warm up so I expect to see some amount of thermal drift. 

[joeqsmith]

I set the LiteVNAs IFBW to 800Hz and let it log for a bit over 2 hours.   You can see I didn't have it tuned up quite as tight so we see it swing both directions. 

I think to narrow it down, I would just run it with the old Agilent.  That system is locked to the GPS.   I could tune the cavity below 9GHz and run it direct to remove the extender.   

If you start seeing me post gold plated parts, it may come to that but for now, good enough.   

[coppercone2]

too blingy for me

 I love gold. The look of it, the taste of it, the smell of it, the texture. - I love gold so much.....

[joeqsmith]

too blingy for me

Better Q. 

[coppercone2]

Gotta start calling it g factor when it comes to gold plated waveguides

[joeqsmith]

The vintage HP adjustable short has a lot of hysteresis.   The new design will use a Starrett micrometer to set the plungers depth.   I honed the plunger and tried it out to make sure that I have enough adjustment before I make the mount for the micrometer. 

[joeqsmith]

Made up an end cap for the micrometer and tried it out.   

[joeqsmith]

Before I take it all back apart,  I wanted to repeat the drift test.  So once again, I tweaked tight and let it run for about an hour.   Again, about a 20dB shift.

[joeqsmith]

While I was confident this is the LiteVNA,  I wanted to prove it.  So, I left everything running and tuned the cavity again and again normalized the data.  I let it run for several minutes than blew the heat gun over the LiteVNA.  Nothing major.  It still has the plastic protection over the LCD and that didn't deform. I just wanted to if a slight change in temperature would effect it.  Sure enough. 

[joeqsmith]

Counter is referenced to the GPS.  LiteVNA directly connected to counter and set to 1GHZ.   Then repeated the heat gun test.   It's too bad the LiteVNA didn't support an external reference but $120.....   

[joeqsmith]

Using the magic T and other parts from the LRL training kit, removed the coaxial coupler to directly measure S21.  Similar to results we saw when using this same cavity with the T and directional coupler.   This cavity does not have near the Q and of course is not sensitive to the frequency drift of the LiteVNA. 

[joeqsmith]

Adding the stub tuner, similar to what I plan to use with my cavity to improve the match, increasing the Q.    Even though the Lite was running for several hours, the drift effects the dip right away.   

My lab partner seems less enthused.

[coppercone2]

I wonder if you put a isolator on there if it would still drift on load, doggy won't care unless you microwave some hot dogs

but useful for power electronics he might smell a early fail way before anything happens on the equipments

[joeqsmith]

I don't think it would have any effect.   In this case we are working with a very low reflections, well, that's the intent anyway.   We are also work at very low levels and the VNA has no problem driving a short or open load.  We even use these to calibrate them.    With such a high Q, the notch is very sharp and any change in frequency will move us towards the skirts.   We could make a little temperature controlled box for the LiteVNA, or I have one that I have made a fair number of modifications to.  I could maybe remove the oscillator and run it from a stable source.   

[joeqsmith]

Directly connecting the LRL setup to the PNA which is referenced to the GPS.  Noise is much lower and I narrowed the span.  Of course the p-p noise is higher but there is no discernible drift. 

[joeqsmith]

I finished up the cavity.  Just in case the LiteVNA doesn't work out and I need to run it on the old Agilent, I opened up the iris to allow it to be tuned below 9GHz.   

Plots showing S21.  Started out tuning it without the sample vial (yellow).  Then inserted the vial (violet).  Resonance frequency drops.  With the micrometer, I can trim the size of the cavitiy to compensate for it and of course have to trim the iris as well.  Left it offset a bit to make it easier to see (red).   

I would like to find some shorter vials but not having any luck.  30-40mm length with a 6mm OD.  Quartz. 

[coppercone2]

very interesting. When you test substances watch out for hydrates I assume that will throw the machine off the most.

I assume water messes with it big time, and many materials form hydrates.

With quartz you can of course pour molten salt in there probobly.

One that might show results could be magnesium sulfate. Bake a portion of magnesium sulfate at approrpiate temperature to decompose the hydrate, and grind into powder, seal in tube. Grind out of box magnesium sulfate into powder of the same consistency and put in tube.

[joeqsmith]

Not too concerned with temperatures as I plan to conduct everything at room temps.   The quartz has much better impurity.   

[coppercone2]

I mean the samples could be hydroscopic and I believe water effects that quite a bit. For inside the tubes. If you bake some salts at the right temperature they will release chemically bonded water and take up a new crystaline form. I could see this messing with someone that is running samples in a microwave field. Some have a few phases of hydration so you can compare hexa to dual to pure say epsom salt

I think its hepta-hydrated (water of hydration), but you can get dua-hydrated and then non hydrated once its hot enough. Its the chemistry thing with the brackets and H2O like chemical*7[h2o]

look at the hydrates section of this page, they are meta stable and it appears dry even if its hydrated (odd property, its not like paper that it gets mushy)
https://en.wikipedia.org/wiki/Magnesium_sulfate

If you read the whole page you will want to attach a refrigerator and a pressure chamber to your sample... so much fun from a box of epsom salt, there is so many configurations. Ice is like that too I think. Just don't make ice-9 (ima call it α-ice9 because we found a boring ice-9 already in some lab), at least not on this continent please...

[joeqsmith]

I mean the samples could be hydroscopic and I believe water effects that quite a bit.

Yes, by definition the hydroscopic sampled would indeed absorb water.

A while back you had mentioned a spectrometer project. 
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4844993/#msg4844993

Doing a quick search,  ChristofferB from Denmark had started several threads scattered over several years but failed to show any results.  I have complied a list of their threads to make it easier to located.   You appear to have engaged in a few of them but I never saw you post about any hardware.  ChistofferB hasn't posted in a few years.  I checked out their YT channel but it's been a few years since they uploaded anything.  Have you actually attempted to replicated such an experiment?   Consider posting about it if you have.   

May 2017,    https://www.eevblog.com/forum/rf-microwave/x-band-transparent-stick-for-diy-electron-spin-resonance-spectrometer/
Sept 2017,   https://www.eevblog.com/forum/rf-microwave/diy-epresr-spectrometer-general-overviewdummy-load/
June 2019,   https://www.eevblog.com/forum/projects/annealed-cast-iron-as-magnet-pole-pieces/
June 2019,   https://www.eevblog.com/forum/projects/diy-nmr-(nuclear-magnetic-resonance)-spectrometer/
Aug 2020,    https://www.eevblog.com/forum/rf-microwave/x-band-cavity-design-and-microwave-safety/
Dec 2020,    https://www.eevblog.com/forum/rf-microwave/microwave-frequency-response-like-its-1971/
March 2021,  https://www.eevblog.com/forum/projects/diy-nmr-best-way-of-driving-a-swept-magnetic-field-between-two-solenoids/

I had read a paper about Zavoisky after reading Southworth's book.   He was a ham and thought, hey, what if...  Interesting project. 

[joeqsmith]

I had tried a few different experiments using the waveguides and VNA to look at how different stuff around the house absorbed RF.  This was the previous jigs.   I was trying to see if I could use the T as a bridge to compare vapors with air and detect a difference.  That was the use of the Kapton windows.   

While I have some data I could post if you would like to see, seems rather pointless so far.   No plans for any videos just yet.

[coppercone2]

not even close, I am still waiting for the wave guide parts I put in a month ago to show up from the other side of the planet, and then I expect a 2 month delay to send back the incorrect wave guide parts that were sent to me   

and hopefully I will be distracted by the 18 month tig welder fix I think I achieved, the silicone conformal coat came in today and I washed all the transformers etc so maybe I can put that machine back together, inspect the solenoid, measure some crimps and finally try some welds

and for chirsb, I bet 99% chance IIRC he was working on the same thing at work. do the same thing at work and at home and your gonna stop working in either work or home because its just too much. if its well funded you end up feeling like you are trying to replicate a cost sensitive version of what you are doing at work at home and that is not that interesting for most people IMO, or the opposite if your boss is mad greedy and you figure out you are jumping through hoops and playing games at work because a few things are 'neglected', and then its like time to turn the brain off before I figure out how bad the situation really is

or #3, you actually might invent something and get burglarized by a corporate lawyer because of that thing you signed that loosely states you invented it because of the company and you don't have the legal muscle to defend yourself, even if its some irrelevant crap that they tried once like 10 years ago and forgot about until they saw you make money

[joeqsmith]

There is that one salvage yard I posted who has a large assortment of waveguide parts.  The problem, they do not provide any details about the dimensions.  If I lived in the north east, it may be worth a road trip just to go though their inventory with a micrometer.   

A neodymium magnet next to the cavity and iris.  The nuts, cap screws, spring are all stainless.  A lot of copper, brass and silver.  The only thing ferromagnetic is  the ground shaft of the Sterritt micrometer.   

With the limited travel and the micrometer, compared with the old HP adjustable short, it's much easier to tune.   There is also very little backlash, unlike that 1950s HP part. 

***
When I first started out, I did not have to sign an NDA.  I remember reading about two soft heads that worked for TI that had taken home the software they were working on.  TI got search warrants and then sued them both.  Their defense was they found the work interesting and saw no harm in taking it.   Now days, it's more like this:

[coppercone2]

did you get the rotating or non rotating head micrometer? Probably does not matter. I mean the starrett that has a key in it so the shaft does not spin and just presses

[joeqsmith]

There's an old Varian water cooled magnet on eBay if you're looking.    I tried to find some data on it but no luck.   2 Tesla?  3? 

https://www.ebay.com/itm/371320266536?hash=item5674699f28:g:PtcAAOSwqu9VR--D&amdata=enc%3AAQAIAAAA8FoscPmUaJO22bDxvDTmFxI5XuPxCHyvkIXzN0m82qg1SiugPbVzwPAEwGElT98IjwSzsJoC0B8nyQbAJP6Tg91%2BJ%2F0Gc2mEIhBFemDEqrjtyFDWMuPy8VDwmRhj2LTnjXdhUdyC%2Fj9Afc5XHslaIPaJkGOjrmC2nrSZ1ssktzLLegFgTvzAS5GPCZ9r7dhdC%2Fsf%2BHV9HEjk2z%2BaIimZWZ4di1wyc2d04kIXNEQkRmZL9iwxllv7JqShbw1xD8g8Za%2FedlB9T3Y6amhdj7X6MQyQmzx1x%2FQeECNlYgNvU0tarm1Pm5%2BHjlSpJoWxBequXg%3D%3D%7Ctkp%3ABk9SR7DlwceMYg

[coppercone2]

lmfao need a fork lift first

[joeqsmith]

I imagine the power supply and other equipment that went with it at least doubled the weight.  Your friend ChristofferB was talking about using the X band.  I assume that was partly due to the lower field requirements.  Old though, I never saw once where they measured the field or showed the sweep in operation.   Maybe they were further along than I was able to find but it seemed like more a 4 year thought project.   

[coppercone2]

well I think he is a grad student iirc so the project budget may have been diverted to basic essentials

[joeqsmith]

That last post I had found, it seemed like they had ditched the original idea and started to go in a different direction.  A few people chimed in, including yourself but that was it.   Their signature states "Chemistry phd student!"  but I assume by now they would have graduated. 

When they increased the frequency, I assume they knew they needed a field 3X.  But I didn't get the tiny little coils they show having near enough to get the offset they would need.  Maybe. 

[coppercone2]

Oh, lol maybe they got a old one when the first job company replaced the older one to keep their yearly budget

[joeqsmith]

Or they eventually realized it wasn't as easy as they first thought and cut their losses.   

[coppercone2]

well every picture I see of those x band type machines they require a fork lift for installation. I never really bothered to figure out what the magnet would look like, I just put the project on the back burner because I figured something ugly would present itself there in some form.

I do like the high current low voltage circuits though, but the biggest I went is that 2000W resistance brazing transformer, though for all its worth I suspect that if I just figured out how to use that in all its capabilities to save on acetylene it would just come back to haunt me when I forget to exercise the gas valves and I need to replace baffles and shit because the tanks go unused for too long. And the wires are too damn heavy,. rather use the 'light' cobra torch, I start thinking of arnold swartsnegger when I wire up that vutron super 0000. That little spot heater I cobble together makes you feel like you are a power loader. I just need to strap the transformer on my back and replace my hand with a large knipex pliers wrench and I am ready for work.... that would be a good exo skelleton too, two pliers wrench hands connected to giant current transformer so you can heat bend I-beam and shit.

tldr: holding objects with heavy hoses or cables makes you feel like a robot

[joeqsmith]

There is a display of Zavoisky's lab where they have some of his original magnets.   It appeared that ChristofferB was planning to use a combination of fixed magnets and pole piece to get the minimum field, then use a coil to make up the difference and allow them to sweep it.   This would really scale down the size and power required.   

[joeqsmith]

I tried an on-line calculator to pick some magnets but in the mean time, I took a couple I had and placed them around the section of WR90 as shown.  The center of the guide measures about 1900 gauss.   I calculated what I would need for a coil but for fun just chopped up a solenoid I had and set the gap to roughly a half inch and got about 500 gauss in the gap.  So, it does appear that we could make a programmable field that wouldn't require a lot of space or power to run it.   I would need to add support to my software to control a power supply to drive the coil but that would be trivial.

[joeqsmith]

Attempt to 3D print copper and sinter it.   Interesting idea but doesn't look like we can pull it off with our setup.     

[joeqsmith]

Still looking for a better coupler to replace the old Narda part I have been using to measure S11.  The Narda 3095 looks like it would be a good fit.  Cheap, covers the X-band and good directivity.   These use the APC7.  There are some <$15 USD from China.  Searching this site, someone had asked about them a few years ago but I don't see any data.  They advertise them good for 6GHz.  Wonder how they perform at double that frequency. 

https://www.eevblog.com/forum/testgear/apc7-to-sma-adapter-from-china-ok/


Cheap APC-7 SMA adapters from China.
https://www.ebay.com/itm/314581375697

Datasheet for couplers
https://nardamiteq.com/product-spec/097-Couplers.pdf

3096, directivity 25dB
https://www.ebay.com/itm/304867686545

3095, directivity 33dB 
https://www.ebay.com/itm/304898554282

[coppercone2]

Wow you can sinter with a extruder printer?

I am guessing its a high copper content 3d print wire that is then baked in a kiln for burn out and sintering?

I am just waiting for my ground cable to come in for the tig lol, got the wrong gas lens in my kit so I only have the quartz one.

I think usually they say that out side of the frequency band of operation for the next octave you might be able to find a stable narrow region of operation that is potenitally usable in spite of the 'modeing' that occurs. But I have no idea for the band under. I think its potentially usable at a higher frequency for some small random bandwidth, but not with the lower end.. that is a hard cut off I think? Wavelenght too small for wave guide = odd transmission modes, wavelenght too big for wave guide =? (I think its very high reflection but not sure)

from what I understand : the most out of bounds components you have (operating past their max frequency) the less likely you can find a useful transmission band, since each component might have a random area that transmits some frequency but they are not correlated so with more then 1 component you might not have a path through.

[joeqsmith]

I would say we tried to sinter with an extruder printer.   Yes, as you described.

All of the parts for that extender are fine for the X band now, except that coupler.  Even at 11GHz, it works better than I would expect but this is really the problem.   The mixer's IF is limited to 4GHz but right now, I can't even sweep up that high.   

https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4850513/#msg4850513 

Thinking I may add in that terminated SPDT relay as well so we don't have to move cables.   Eventually, it needs to get mounted into a box but for now I'll leave it as a 3D mess. 

[joeqsmith]

Try finding couplers with over 25 dB directivity.   They are not common.  I want to keep the coupling at 10dB and plan to give up the half dB loss by leaving it in-circuit.   HP offered the 33311B relay with a 5V option.  It seems like it would be a good fit.   

https://www.ebay.com/itm/144419029196

[coppercone2]

here is a 50db coupler
https://www.everythingrf.com/products/waveguide-couplers/flann-microwave/228-248-16133

hidden behind a quote wall.

it appears they are quite long for higher directivity

A 779D or similar is like 30dB.

https://www.romtekonline.com/product-details/multihole-directional-coupler.html
35

might be worth checking the Flann brand out on ebay, they seem to be all that shows up for higher db directivity

https://flann.com/wp-content/uploads/2015/09/Flann-Final-2015-for-Website-Use-06082015.pdf


your finger sir
https://www.ebay.com/itm/175741081773

[joeqsmith]

I would have thought you would understand that everything on the extender is coaxial.   That said, it would certainly be possible to make it all using WGs, if size, availability, cost, ease of use.....   

[coppercone2]

nope I read that in between trying to clean this p6015 probe for silicone oil with all the high cleanness procedures and totally forgot, at least i did not spill hot oil anywhere yet

I am suspicious that the silver plating on the high voltage resistors disintegrated into the freon or something, there was alot missing on the resistor. I wonder if that could make it arc over

[joeqsmith]

When I designed that wideband HV probe, I didn't want to use anything liquid.   So ceramics and make it large.

[coppercone2]

I saw your point because of thermal expansion and also bubbles. I was gonna squirt a little bit of butane in there before sealing though, just a drop...

might just have to say... avoid probing awfully low impedance circuits. For limited HV stuff, it should just spark inside of the tube. Would I trust this for probing a HVHC transformer.. nope

kinda wonder what CAT rating this probe would have with freon, with oil, and then the proper redesigned one with oil in it.

Kind of think that a very high current high voltage probe that can explode, should have a HV fuse in front of it, whatever that looks like. Or because of bandwidth reasons, a minimum safe distance... ship it with a tape measure....

[joeqsmith]

kinda wonder what CAT rating this probe would have with freon, with oil, and then the proper redesigned one with oil in it.

Sounds like you bought the 6015 probe without reading the manual first as.  Even without the manual, just looking at the probe I would never have come to the conclusion that this was a good choice for AC mains work.   I take it you have little experience in this area.  This probe is very popular and I bet if you used the sight's search engine, you would find everything there is to know about it. 


***
I have an Agilent 33311 that would work to switch between S11 & S21.   Isolation is good but the insertion loss is about a half dB.   I pulled it out and it is marked Agilent, so it would be newer with potentially less wear but its an A.   

https://www.testequipmenthq.com/datasheets/Agilent-33311B-Datasheet.pdf

[coppercone2]

I read the manual it says nothing about how big of an arc it can take before it explodes and shoots hot oil (for the 6015A). Say there was a surge on the power lines.

I assume its meant for lab use like from small transformers and such, since its made by tektronix. I.e. bench top isolated circuits. For a house I assume it would arc over some where in the breaker box if that happened anyway like a spark gap. But past the house I don't think I would trust it.

For the A it does say The inputs are not rated for connection to mains or Category II, III, or IV circuits, but for the 6015 it does not have a cat rating

[coppercone2]

for the oil fill I used silicone oil that I heated in a beaker with a watch glass on top to 150C for like two hours (using immersion thermometer), let it cool down to be manageable then I passed it through a glass frit vacuum filter into a glass flask (washed and baked all of that) because there was some particles in the oil that I noticed after heating and inspecting with bright light, then poured that into the probe that was washed and baked. Not sure if dust got past the watch glass or the oil was contaminated.

It should probobly be dried in a retort but I don't have one (like the old soup & life biology experiment

[joeqsmith]

I read the manual it says nothing about how big of an arc it can take before it explodes and shoots hot oil (for the 6015A). Say there was a surge on the power lines.

I assume its meant for lab use like from small transformers and such, since its made by tektronix. I.e. bench top isolated circuits. For a house I assume it would arc over some where in the breaker box if that happened anyway like a spark gap. But past the house I don't think I would trust it.

For the A it does say The inputs are not rated for connection to mains or Category II, III, or IV circuits, but for the 6015 it does not have a cat rating

We had the freon filled ones when I started out.  There were no CAT ratings back then and so it should be a surprise that the manual does not mention them.   

I have never seen a company say anything about how big of an arc their CAT rated DMM can take before it explodes and shoots hot ....  It's just not something anyone is going to publish.  Again, thinking this is all new to you as I can't think of one time anyone has made such comments about the 6015.  Yes, we have always used them in the labs where I have worked.     

I thought there was a derate curve for the older probes when running them dry.   Personally, if I didn't work with these higher voltages, I would run them dry. 

The later probed we have are filled with a solid, so no maintenance.   I have it's little brother at home that also does not use freon.  I had pushed that probe past the limits several times but eventually made that wideband HV probe to work at these higher voltages. 

Sounds like your interest in HV far exceeds any interest in the thread topic.  You may want to consider starting a new thread in the test equipment area to discuss restoring your probe as I doubt many people are following this particular thread.   You may find a people willing to help out once you make it visible to them. 

[joeqsmith]

Shown with a Narda 3095 installed on my extender.  Added some support for the amplifier and also made a section of semi-ridged to connect the coupler's input port.  I have not yet decided on adding a relay.   

The coupler made a big improvement.  Plots showing the data I had previously collected with the extender compared with the update.  I used the same homemade standards and Agilent X11644A coefficients  to calibrate the VNA to 12.1GHz.   I had only swept to 12GHz before as the performance was so poor.   The mixers only support an IF of 4GHz and as the range is increased beyond 12.1, the performance starts to degrade quickly. 

Decided to roll the dice on used Amphenol connectors rather then trying the Chinese ones.  I was a bit worried they would have just been a waste of time.   

[msat]

Hey guys

I know this is somewhat off-topic but I felt this is the best place other than maybe a new thread to discuss this.

I finally got around to doing a little microwave experimentation. However, since I never jumped on some crappy but cheap-ish ebay WR42 horns for my coax to waveguide adapters when I had the chance, and been somewhat reluctant to 3d print (and paint) some, I instead opted for a couple of ~10GHz gunnplexers. In my recent experimentation, I used one as a transmitter, and then measured the output of the detector diode on the other which is thus used as the receiver. 

As you can hopefully see in the attached image, I printed a mount for them that allows me to adjust the angle on the longitudinal axis from 0 to +/-90 degrees in 22.5 degree increments, with the center of rotation being the center of the gunnplexer.

So in my little experiment, I was getting some baseline voltage reading at the detector when both tx and rx were oriented at the same angle (same polarization), and then measuring the decrease in voltage as they're rotated relative to one another. I wanted to compare and contrast this with what polarizer experiments seem to show.

At 22.5 degree relative angle, the received voltage is 75% of baseline. This makes sense from a trigonometry standpoint. At 45 degrees however, it drops to 25%, which is not expected. These results are consistent regardless of distance between tx and rx, and the way I orient them to get the relative angle differences. Right now I'm thinking these unexpected results are due to my hardware. Soon I'll be modifying some satellite LNBs, specifically because they use round waveguides/horns, to perform the experiment with. However, I was also hoping someone here could duplicate the experiment on their hardware and post their results if they could find the time. Any of you guys willing to do that?

[joeqsmith]

Far more on topic than much of what has been posted.      Walter Lewin had a lecture on this.  Lucky for us, MIT/France could not purge the internet of his content.   In the video, he conducts a demonstration starting at about the 1 hour mark.   

For off topic, I would have liked to have all the details about that sexual harassment case.   I can't imagine anyone who would self-mutilate rather than simply dropping a course and turning off their PC.  I searched her after the fact and while I don't know enough to form an opinion one way or the other over the case, I am glad that we still have access to the content he created.
https://www.govinfo.gov/content/pkg/USCOURTS-mad-1_16-cv-12394/pdf/USCOURTS-mad-1_16-cv-12394-0.pdf

[joeqsmith]

During my short visit on the V2Plus group.io, I had noticed someone asking about using theirs to measure waveguides.  The advice given was IMO poor as obviously anyone following this thread would know.  I attempted to post a comment to them but sadly, they once again censored it and it never showed.   

IMO, people who actually want to discuss the V2Plus4 should just ditch that group.io reflector and use a different group or forum.   

https://nanorfe.com/forum/using-V2-plus-4-Pro-for-waveguide.html

[msat]

I have watched that lecture by Walter in the past, among other ones of his. However, it doesn't provide the data I'm interested in unless I guesstimate it. I've tried to do this on a few other videos with similar demonstrations, but it's unsatisfactory.

I've been wondering if part of my issue the way I'm interpreting the values from the detector diode. I'm merely hooking up a volt meter to it, while the gunnplexer itself has the diode shunted to ground via a 1k resistor and a zener (it was there when I bought it).

Per https://www.qsl.net/in3otd/electronics/power_detectors/power_detectors.html "As known, the diode detector output is proportional to the square of the input voltage/linear with the input power at low power levels and becomes proportional to the peak voltage/square root of input power at higher levels."

I'm still trying to wrap my head around that, and how relevant it is. Like I said before, the results are the same regardless of the distance between the tx and rx (which does have an effect on the baseline voltage reading).

Tangential to this, I got my couple of "Ku" satellite LNBs in the mail, which I ordered new from amazon for ~$10 each. I was a bit premature in my purchase, neglecting to realize such new and cheap parts were highly unlikely to use dielectric resonators or really much of any discrete circuitry, making electronic mods pretty much a no-go. To top it off, naturally many of the passives are among the smallest SMD sizes available. I then thought that *maybe* I could hook it up to my TinySA Ultra and use that to measure received power, but in the almost non-existent spec sheet for the nearly all-in-one LNB IC, it states that it does some automatic gain nonsense, so there goes that idea too  The only usable component may be the waveguide, but then I need to figure out the electronics, and I don't currently have a suitable LO source, mixer or LNA. Maybe I should just go the diode detector route?

[joeqsmith]

You should start a thread for your project.  I would provide details about the goals you have in mind, your background, work you have done so far.    Others may have a similar interest and chime in.   

Problems with using this thread, it long and people don't take the time to read.  It's difficult for readers to locate sub topics.  Then, I started the thread to cover some basics on waveguides.  Anyone reading from the start may loose interest and never discover your project.   

To be clear, I don't mind you posting here but rather just offering a suggestion if you are looking for help on how to increase your exposure. 

[joeqsmith]

Finally got around to mounting the HP33311B relay. 

[xrunner]

We're both proceeding at a snail's pace. 

[joeqsmith]

Slow indeed.  With it being used,  I had to test it first to make sure the performance was still good enough.    I've thought about mounting it all into a box to make it a bit more robust and take up less room.    There are some nice extruded aluminum cases but that coupler and cables would need about 10" depth assuming I let the APC7 connector extend outside the box. 

[joeqsmith]

Roughly $50USD from China.  The faces are a bit thin and I think I would machine a new face for the front with 1/4" plate aluminum.   Something to ponder over the winter.   It's a lot of junk to cram in that small box and I would want some decent bulkhead connectors. 

[joeqsmith]

My plan is to make it a clam shell so the two boards fold up.  A while back I had posted my attempts to repair a damaged semi-ridged cable.  Thread shows the bulkhead connectors I plan to use. 

https://www.eevblog.com/forum/rf-microwave/is-is-possible-to-repair-a-hairline-crack-in-semi-rigid-coax/

Decided against running the the APC7 through the case.    All the RF connectors will be routed to the front,  P1 to the bottom left,  P1extended to the top left.   Single toggle switch will also be mounted on the front to select between S11&S21 maybe in the center, along with the 10MHz reference clock input.    Power connector may be off the rear. 

[xrunner]

Looks very professional so far. Almost like ... you might even know what your doing. 

[joeqsmith]

Made up the bulkhead connectors.  There will be a set of cables in the read that tie the boards together.  Looks like things should fit.   Of course, I get it to look nice, the performance will go out the window.   

[joeqsmith]

Mounted the parts on the lower board and made up cables for it.   Stacking the two boards, there's a good 10mm to spare.    Still debating to route out the APC7 or not.   I'm not liking the idea of stacking all those connectors.  Unlike the ham in the photo who placed several connectors in series,  at 12GHz it may present more of a problem.

[xrunner]

LOL I dispelled that myth myself a few years ago. The HAMs would say "Don't use an adapter in-line because it'll cause a few dB of loss!"

I connected seven misc adapters together and ran some tests. Tests? Tests? How dare you actually try to see what's really happening!

 

Turns out it's all BS advice. At HF seven adapters causes less than 0.1 dB loss, and at 144 MHz around 0.3 dB loss.

They don't say that anymore. 

[joeqsmith]

Looks like that video is 3 years old.  Skimming his video, looks like he may have tested to 30MHz and saw a 0.12dB loss. 

I may put everything together and compare it against the data I already collected. 

[joeqsmith]

Looking over his videos, it appears someone wrote him about it.

[xrunner]

Well, let's put it like this. I used adapters that were in good condition (what other kind would I have?  )

If you connected a few adapters used in the field, like up in the air for 10 years, with no waterproofing, with no care in the world, yea you might get a higher loss. But that's not the fault of the adapter, it's on the HAM's maintenance habits.   

[joeqsmith]

I was imagining someone using RG174 and SMA connectors.  They check the loss with their VNA or other and measure some small loss.    Then they connect it to their 2kW amp...  Should be fine...     I'll just crank up the power to compensate for the losses...

Remember that gold plated PL-259 to N adapter I used as part of my homemade Watt meter testing.   I was seeing a pretty good temperature rise with it even at 300W CW (or what ever I was running).  Wonder when it goes into thermal runaway. 

Anyway, my point was while we are dealing with small signals (<10dBm), the frequencies are in the 8-12GHz, not <30MHz.   

[xrunner]

Joe are you using in your project semi-rigid coax? It all looks like hardline. I think I want to try my hand at making up some semi-rigid lines with SMA connectors. So I wanted to know if you had used that type before. What do you use to cut the ends with? I plan on looking at some tutorials in the next few days.

[joeqsmith]

https://www.fairviewmicrowave.com/rg402-type-.141-semi-rigid-coax-cable-tin-plated-aluminum-fm-sr141altn-st-bulk-p.aspx

[xrunner]

RG-402 + SMA connectors ordered. 

[joeqsmith]

Don't waste it on that DC stuff... 

Ended up just drilling out the end that came with the case.  Seems sturdy enough.

[xrunner]

Don't waste it on that DC stuff... 

Oh no, I'm going to use it for the FWD and REV RF out of the coupler. I think the short coax cables that I'm using are OK, but I want to try my hand at something new. 

[joeqsmith]

I was thinking < 500MHz was DC and you need a new project.  Maybe some 3D printed waveguides. 

[xrunner]

I was thinking < 500MHz was DC and you need a new project.  Maybe some 3D printed waveguides.

Oh shucks! I had a project that went up to 450 MHz and I'll be damned if you went ahead and defined everything under 500 MHz as DC! I see how you play now. Well, now I'm thinking about laser communications next so we'll see where DC is defined then ... 

[joeqsmith]

Sure, but I don't see how that new coax fits into the picture.   

[joeqsmith]

Thought about adding something like a 9-pin D shell for power and future expansion (maybe allow my software to control the switch).  But ended up with a simple phono jack for power.   Stuck it on the front so all of the connections are on one side.   Needs hardware to mount the SMA to the plate along with new labels. 

[xrunner]

Phono jack for power? Sure as long as you own it it'll be fine. Otherwise better label it or another owner will want to listen to the thing working. 

Photography nice - good presentation setting on the table. Hey what's in the bowl?

[joeqsmith]

I was thinking if I did decide to control the relay, I would swap out the phono jack for a mini DIN.   Mechanically it will fit in that area.   9-pin D would be a lot of wasted space.   I've used phono jacks for power before,  like this amplifier that I used to demonstrate one potential problem when using these low cost VNAs with their squarewave drive.  Note the battery holder is stored with it and the connector is marked.  Even my design scribbles are in the bag.   Just in case after my death my wife holds a big sale and a ham buys it for 5 cents.

The table was made by my grandfather and the bowl and egg shapes inside are Alabaster from Egypt. 

[joeqsmith]

Making a basic checkout, seems no worse for the wear.   So for fun, I connected a decent GORE cable to the converter and attached it to a 23 inch section of that semi-ridged RG402 that I used to wire it with.   At 11.8GHz, I measure about -4.4dB.  No attempt was made to calibrate the system as I was really just interested in a relative measurement.

Next I replaced the semi-rigid cable with one of my unused cables supplied with my V2Plus4.  If you follow the channel, there was segment where my test setup slowly falls off the desk dragging the VNA to the floor by the cables.  These cables are not the ones used.  I had two sets.   These are about 12" long.   Notice I loose about a dB.   

Last, I placed a Weinschel WA3 3dB attenuator in series with the V2Plus4 cable.  This attenuator has a spec'ed frequency range of DC - 12.4GHz.   Like magic, it measures about 3dB lower. 

So the semi-rigid cable you purchased can certainly improve the losses if you decide to go that route but it's a one-shot deal.  Make sure you understand that it is easy to damage, like our friend here learned, and I gave it my best shot at repairing it with no success.   It's also a pain to put together.   

https://www.eevblog.com/forum/rf-microwave/is-is-possible-to-repair-a-hairline-crack-in-semi-rigid-coax/

I ran a few checks of S11 as well and I think we are ready now for some labels....

[joeqsmith]

Here's a stupid test for the fun of it.  It's my spin on the Jim W6LG videos showing how much loss connectors have in the HF bands.   We all know not to use transmission lines beyond their cutoff but I did say stupid....   
https://www.microwaves101.com/encyclopedias/coax-cutoff-frequency

Tuned the VNA to the lower end of the extender and inserted a SMA thru.   No attempt was made to calibrate the system.  Like before, I just looking at relative numbers.   Measure about 0.5dB. 

Next I replaced the thru with 12 BNC adapters, including two SMA to BNC adapters.   Measured about 2.5dB lower. 

Last stuck in a Midwest Microwave BNC attenuator PN# ATT-0313-06-BNC-10 into the mess.   Measured about 9.3dB.   
https://www.mouser.com/datasheet/2/643/pi-CCS-MW-ATT-0313-06-BNC-10-1312565.pdf

Nothing real useful from our Baby N Connectors.  I did qualify with stupid.   

[joeqsmith]

Been waiting to run this test because the SMA wasn't yet secured to the front panel. 

Connected the extender directly to my microwave counter and set the LiteVNA to 500MHz CW.   The PDRO is at 7.86G (just below the X-band).  We should measure 8.3600000GHz but the counter measures 8.360019671 and it's hunting....... Imagine that...

Connecting the extender to the 10MHz GPS reference,   get the counter measures 8.359999964 and is stable within a count.  The rest of the error is the LiteVNA's internal clock.  Too bad the VNA doesn't have a reference input as some of the experiments I was attempting, the VNA's drift comes into play. 

Good to see it all working again.  Time to clean up the mess..

[joeqsmith]

When I first swapped out the directional coupler for something with better directivity, I plotted how it improved the noise floor.   
https://www.eevblog.com/forum/rf-microwave/experimenting-with-waveguides-using-the-litevna/msg4903016/#msg4903016

You can see there are some areas where you can get much better dynamic range than others.  Attached for example, running some attenuators from 0 to 70dB to get an idea of the linearity.   Finger tight and normalized thru.  Mix of my very low cost Chinese attenuators.    Typically its going to be around 50dB and worse case looks like maybe 40dB assuming 10dB headroom.    Not great by any means but far better than trying to use the harmonics at 12GHz and good enough for my home experimenting. 

[joeqsmith]

I did try repeating an earlier test stacking some 10dB MWM attenuators in series.  These are still just jelly bean parts but a bit tighter tolerance.  Parts were torqued.  For the 3 and 6 dB, I used two other name brand attenuators I had.   This is really about what performance I expect out of it.   

[joeqsmith]

Running a SOSL cal with my homemade standards and measuring the return loss of the terminator supplied with the university microwave trainer.   Swept it from 7.9-12.5G just to get a better idea how it performs.  Not great but cheap. 

Note the three sets of data are from my original PCB construction prior to the new case, and with both the old and new directional coupler.   

[joeqsmith]

Using Dislords firmware, the LiteVNA supports I think unlimited harmonics, or at least way beyond what is useful.   If I wanted to measure S11 directly rather than using the frequency extender,  at least for the X-band and my particular versions of hardware, we can't.   Using the supplied cables, short, open and sorted mini-circuits load to calibrate the VNA from 1M to 9GHz.   Plot showing the return loss with the standard attached.   Even at 9GHz, the return loss is basically 0.

[joeqsmith]

With the Narda waveguide load attached, about the only thing we can see is where the low frequency cutoff is.   Still, below 6GHZ where it was designed for, it has decent performance and I am not aware of anything else in this price performance range.   

[joeqsmith]

Tried to locate a good condition, used N to SMA adapter for port 2.   They are out there but the high costs made them not worth the risk.   At 12GHz, no point in trying the low cost Chinese parts.  Ended up buying a new Hirose  adapter and called it good enough.

https://www.digikey.com/en/products/detail/hirose-electric-co-ltd/HRM-554S-40/5148329

[joeqsmith]

The work of Jagadis Chandra Bose. 

https://www.cv.nrao.edu/~demerson/bose/bose.html

[joeqsmith]

One problem with playing around with used waveguides is finding data sheets.   Most of the cold war military contract houses are long gone, along with all the information for their products.

I've been looking for a isolator with decent isolation specs.  People who are selling such devices are not typically going to have the means to measure them.  So you are basically going on a blind date.   In this case, looks like I may of gotten lucky.   Using the frequency converter with the LiteVNA, I measured an insertion loss of <2dB and isolation > 26dB.  The low quality transitions were clamped on and I doubt very much the insertion loss is this poor.