CB and Ham Radio Techs Love Their Bird Wattmeters

[xrunner]

This is the CAD model for the case front panel (the rear has the same basic shape), duplicating the original. The originals are not exact rectangles. They have an artistic (I suppose that's what you would call it) stretch in that the center span of the long length dimension is 1 mm longer at the middle, on each end, than at the top or bottom. Doesn't seem like a lot to me, but whoever designed the case thought it looked just perfect like that. It exists, so I made them the same way.

One opening for the OLED, and one for the band push-button switch. The OLED will mount on four raised pins.

[xrunner]

The Due board needs to be mounted on a second level, so that the PWR jack and USB ports are at the rear. So I'm thinking about that now. I experimented with adding three stand-offs to the bottom plate. At the top of these I will install M3 threaded brass inserts. Then the top plate can be held in place using M3 screws. Looks like it will be workable.

Top plate not designed yet ...

[xrunner]

Yea I'm still working on it ... 

I got the top plate mostly done. This is where the Due board sits - on top of three stand-offs coming up from below where the RF parts are located. The top plate has slots where the mounting hardware goes through. This is so it can be pressed up exactly to the back of the rear case panel.

There are three mounting holes in my plate for the Due board, and the plan is to use M3 brass inserts in them for the bolts to go into. But why only three bolts - aren't there more mounting holes in the Due board than that?

Yes there are - six total. They are sized for M3 hardware. But I really don't need to use all the holes for one thing. The other thing is - there is not enough clearance on more than one screw hole for the head of the bolt. It will not go past the header. I have seen this before on the Uno boards and as well on the new R4 Minima boards. I do not know why they put some of these holes so close to other parts. I suppose greater minds than mine know why.

I ordered some new PLA from Atomic filament. I'm going for a certain color scheme. The original case is gray. I have a yellow OLED display. So I thought I'd have the other case parts black. They have a new type of black PLA filament that is more, uh, blacker-er than the previous black -

The darkest, most true tone black filament. 6 months in development with our color supplier, an extremely pure black colorant with no off shades of grey, not carbon black based. Full synthetic color formulation.

Extreme JET BLACK filament

Maybe you thought black was a simple thing? 

[joeqsmith]

The original case is gray.

Bird gray I hope.

[xrunner]

The original case is gray.

Bird gray I hope.

Of course! It's the color - that's how it all got started. 

[joeqsmith]

Had to change the coin cell in one of my scopes. Recently I had used it and noticed the corner had cracked.  Scope is on a shelf and remains covered.   Guessing age.  I had glued it.   To get to the battery you have to remove the bezel.   While taking it off, the glue joint fails and about a 1" section of plastic falls off.   Looking at this area, the bezel is VERY thin and I am not at all surprise it broke where it did (where screw fits and sharp corner).  This time I tried to melt the plastic which worked so I fused a lot of new plastic into that area and built it up. Then used the dremel to reshape it with a bit of sanding.  The plastic I used was not the same color and I mixed some blue, white and black.

If you're going to own LeCroy scopes, you need certain skills.  Matching factory colors is one area I could use some improvement!   

It did get the new battery.

[xrunner]

Well that's not a bad repair. I need to start 3D printing what I've designed and start checking if it's all going to go together like I planned - of course it won't on the first pass. Even before that I have to print out a set of test holes of increasing diameters to find the right size holes for the M3 and M4 heat set inserts by testing how the insert goes in.

I'm looking at next week as the heat wave is going to subside finally. I have my projects and the neighbor kids have some things they want me to make. The boy wants me to 3D print him a model of a hand grenade. They are available on Thingiverse. Not sure where that kid is headed in life ... 

[joeqsmith]

Should at least be mechanically stable now.  A very minor repair compared with the other plastic LeCroy.  That thing was a mess but after fusing all that new plastic into it, it's not had any new cracks show up. 
 
A new post from the hams asking about TDR, taken from:
https://groups.io/g/nanovna-users/topic/length_measurement/100919376

If I set the stimulus start and stop to 50KHz and 1.5GHz the transform maximum length is shown as 19.36m. If I set the sweep to 401 points what resolution and accuracy can I expect, provided that I have the VF entered correctly.

1936mm/401 equals just over 4.8mm.

Thanks,
Geoff -- AB6BT

I read through the posts that follow and was reminded of the ham who suggested that using 7 or so data points would increase their resolution.      Enhancing the art....

[joeqsmith]

As long as it's a question on their test, hams are at least forced to read it and remember it long enough to pass their exam.   

In practice, the basic limitation is inversely related to data collection bandwidth in the frequency domain. A rule of thumb defines resolution on the order of 150 mm (for air dielectric) divided by the Frequency Span (GHz) . For example, a 20 GHz frequency span will provide a resolution of about 8 mm while a span of 70 GHz will provide a resolution of about 2 mm. So the broader the frequency span, the more information presented during the time domain analysis.

A limitation to the frequency span rule occurs when measuring devices with limited bandwidth. Ideally, the device will pass the DC component, and as a result, the performance at higher frequencies will result in a gradual roll-off. If the DUT does not pass the DC component, such as band pass or high pass filter, then resolution will degrade. Resolution is also influenced by the processing method and window selection options that are described below. Another important factor is the relative amplitude of the signals being processed. A large signal can swamp a smaller signal–where the greater the time (distance) separation between the two discontinuities, the better the points of interest can be resolved.

[xrunner]

As I said earlier, I have to extend the case vertically so the electronics will fit. Something like ~ 20 mm not sure of the exact number yet. But the screws that came with the case are not long enough to go through my yet-to-be 3D printed side extension panels into the screw hole on the other half of the case. It's an M3 screw, but like a sheet metal or wood sort of screw. I could not find the same sort of M3 screw design in the length I needed, so I just bought a box of M3 x 55 mm hex head bolts. They will work OK. I also got a box of M3 button head screws of different sizes on the side.

The temps are finally cooling off around here after tomorrow, so I plan to start up the old 3D printer and get busy!

[joeqsmith]

So you plan to print side cover extenders?  Maybe make the clear, then add a bunch of LEDs to light up the insides like the kiddies do with their PCs?   

Thinking of bad mechanical engineer choices,  that scope that I repaired has a lot of them.  There are adapters that fit onto the scope's front end depending what probes you plan to use.  If you have them installed, you can not attach the dust cover.  So you have to pull everything apart after use.  It's so close and wouldn't have required a whole lot of additional plastic.   It's like they were shaving every cent out of the mechanical designs.   Beyond the ME's, the managers, QC, marketing, sales on up played their part.

[xrunner]

So you plan to print side cover extenders?  Maybe make the clear, then add a bunch of LEDs to light up the insides like the kiddies do with their PCs?   

See this is why it's good to post your projects on a forum, so people can give you great ideas. You're right, it won't be very impressive if I only have a yellow OLED display. A computing device needs more - much more, to show the user how impressive it is inside. A lot of LEDs inside blinking with translucent side panels should do the trick. 

[xrunner]

Progress ...

Today I printed a simple test piece to find the optimum hole diameter for the M3 brass inserts I have. I printed a range of holes going from diameters of 4.6 to 5.6 mm in increments of 0.2 mm. The holes came out pretty close to the designed diameter, but were just a little small. This is not unusual for an FDM printer. Cura slicer has a specific control to compensate for this call Hole Horizontal Expansion. I set the value to 1.0 mm and the next print the holes were spot-on.

The largest outside diameter of the brass inserts is where the knurling is which is 5.5 mm and the smallest dia. of the several outside features of them is 4.7 mm.

I set my Hakko soldering iron with a special tip for installing these inserts to 200 C. The two closest holes seemed to be the 5.0 & 5.2 mm holes, so I pushed in a brass insert into each of them. After cooling, I screwed in a long M3 bolt and applied force in various directions to see if the insert would get loose. Neither of them did. So, since the smaller of the two holes didn't exhibit any signs of excess plastic being pushed out, I'm going to go with the 5.0 mm holes in my parts designs for the M3 brass inserts.

You can easily remove these inserts and re-use them. All you have to do is apply heat again and then quickly screw in a bolt and pull them out. No plastic residue sticks to them and you can simply re-use them.

Tomorrow I plan on printing another test part for the M4 inserts, which will be used for the M4 bolts to hold down the Putnam coupler.

[xrunner]

I made my first test print of the bottom plate design which holds the Putnam dual directional coupler and the two log amps. I intentionally halted the print without letting it go through the entire process of printing the three tall stand-offs. This because I wanted to check fitment and some details and probably make a few tweaks first without wasting too much time and material.

Everything fit well. Now that the log amps can be held down securely with screws, I was able to tell that I needed to move one of the three stand-offs a bit because of the way the cables were laying. But I wasn't far off in my estimates.

So overall, I'm pleased and will now print the entire bottom plate.

[xrunner]

Well in about 4 hours I'll know if this bottom plate is acceptable ... 

[xrunner]

The bottom plate came out really well. To hold it down using the molded screw holes in the case, I designed some custom adapters for M3 screws and washers to widen their footprint.

Next I need to install the brass threaded inserts and get the hardware mounted on the plate.

[xrunner]

Did some design work for the top plate which will hold the Due board. I printed a quick thin layer to check how it was going to fit. It looks OK. The mounting plate is adjustable and can slide back to the rear for a tight fit. The rear plate of the case will have openings for the PWR and USB ports. The rear plate you see in the pics (which came with the case) will not be used.

[xrunner]

Finally got back to the project. Couple of days ago we lost power from 10 PM to 10 AM. If it's not one thing it's another around here.

I made some final changes to the top plate. I needed the Due board PCB to sit above the plate a couple of mm due to the ends of the through-hole component leads which extend a bit below the PCB. Instead of using individual spacers under the PCB where each screw goes, I made the stand-offs as part of the plate. Then instead of inserting the heat-set brass part in from the top, I will insert them into the bottom of the holes. Should work OK.

[joeqsmith]

Sounds like our power before they replaced the lines. 

Your plans are to make a second one still to give to your one friend?

[xrunner]

Sounds like our power before they replaced the lines. 

On my side of the street all our power lines are underground. Across the street they are on poles. I would have thought underground lines would be more reliable, but it doesn't seem so. One time I lost one phase to my house so they had to come out and dig way down and fix that. Other times the local "loop" just cuts out even in nice weather. I have no way of knowing what the crews are doing to fix things. This most recent time there was a bad storm with high wind and a whole lot of above and below ground power losses were caused all over the city. This is why I bought a generator about 4 years ago, so I can get through about 24 hours keeping my fridge cold and perhaps making some coffee. Feels like I live in a third world country at times.

Your plans are to make a second one still to give to your one friend?

Don't know now. He and his significant other actually moved to Fairbanks Alaska two weeks ago. She needed to make a move somewhere to get a higher promotion and they picked Alaska. I don't know how long they will stay. Yea I could ship him one I guess but I couldn't support it if it failed or had an issue I didn't anticipate.

Moreover, he doesn't even need an SWR/PWR meter now. He keeps in touch with the local HAMS with a radio that does what is called "Wires-X" -

https://www.yaesu.com/jp/en/wires-x/index.php

and yet another type which uses DMR radios -

https://www.savenetradio.org/what-is-dmr-ham-radio/

Basically it's VOIP which goes over the internets. To me it's little more than using unnecessarily complicated wireless microphones and has very little to do with the essence of the hobby (the transmitting and receiving of radio waves using antennas for communication). You might as well just use your smart phone and drop the HAM radio stuff. Hell you can do more than HAM radio can by doing a group video call with Discord! A real man, a true HAM, would set up HF antennas and communicate with SSB - now that's real radio.

[joeqsmith]

Our's is all underground and when I spoke with the group that was replacing them they told me the expected life.  Seems like it was maybe 40-50 years.  They said it was beyond its expected life and was planned for replacement.  I think it comes down to how often it goes down.  Just before they started working on it, my neighbor was outside and heard what he thought was a gun shot.  That's not something you normally hear around where we live.  The power went down shortly after.  I expect this was a breakdown below the ground.   I think they told me it was running at 2kV.   

Basically it's VOIP which goes over the internets. To me it's little more than using unnecessarily complicated wireless microphones and has very little to do with the essence of the hobby (the transmitting and receiving of radio waves using antennas for communication). You might as well just use your smart phone and drop the HAM radio stuff. Hell you can do more than HAM radio can by doing a group video call with Discord! A real man, a true HAM, would set up HF antennas and communicate with SSB - now that's real radio.

Agree, but I will add that old time code as well.  If it really were an emergency, nice slow CW may be more robust.   Yeah, I know, new hams no longer have to learn that worthless stuff. 

[bd139]

Interestingly I've been trying to debug a bluetooth problem here for a few months particularly when it's very wet. Just random crap outs. I moved into this place in 2022 and it's a modern build (2010) apartment block. There's an 11kV feed to a substation in the base of the building with buried cables. When you walk past it on a  rainy day you can hear some quiet crackling. Wonder if there's something RFI coming out of that.  I mentioned it to the estate manager and they said it'd been checked and serviced recently.

Oh also don't get me started on DMR and such stuff. Yes, just use WhatsApp or something. At least that works and has humans on the other end of it 

[xrunner]

There's an 11kV feed to a substation in the base of the building with buried cables. When you walk past it on a  rainy day you can hear some quiet crackling.

Crackling coming from an 11 kV underground feed? Nothing can go wrong ... 

Oh also don't get me started on DMR and such stuff. Yes, just use WhatsApp or something. At least that works and has humans on the other end of it 

Yea and a few of the hams get excited when they claim "Hey I worked Alaska last night on DMR talking with our friend who moved there!"

How exciting. 

Seriously, I told him if he wanted to talk or just say a simple "hello!" - just call me or text me. 

[xrunner]

I inserted the heat-set brass fittings into the Due mounting plate, and mounted the board with four M3 screws. So far so good on that part. Brass threaded inserts are the way to go.

[xrunner]

The brass fittings were installed on the bottom plate - 4 x M4 to hold the directional coupler, and 3 x M3 to hold the top plate (microcontroller). Next I am going to install all the components and see how it all fits together.