Some sellers from China on ebay sell kits with PNA trademark.
They wrote in description:
"Accurate electrical models are needed of the opens and short circuits. A number of eBay sellers sell low-cost calibration kits, but these are effectively useless, as they don't have the mathematical models of the opens and shorts necessary to load the constants into a VNA, and we doubt they have optimal phase difference between open and short. This kit is different, in that it is designed, rather than just assembled. With this calibration kit, there is a support page with information on what coefficients to use for Agilent/HP,R/S,ADVANTEST,ANRITSU...".
Price is just 218 USD for SMA kit and looks good generally BUT I'm don't know quality and have no any information about this kits and where to get this calibration data.
I suppose that would be clever to ask him first for characterization equipment and what data they provide for each kit and look for some info if it possible.
Some sellers from China on ebay sell kits with PNA trademark.
They wrote in description:
"Accurate electrical models are needed of the opens and short circuits. A number of eBay sellers sell low-cost calibration kits, but these are effectively useless, as they don't have the mathematical models of the opens and shorts necessary to load the constants into a VNA, and we doubt they have optimal phase difference between open and short. This kit is different, in that it is designed, rather than just assembled. With this calibration kit, there is a support page with information on what coefficients to use for Agilent/HP,R/S,ADVANTEST,ANRITSU...".
Price is just 218 USD for SMA kit and looks good generally BUT I'm don't know quality and have no any information about this kits and where to get this calibration data.
I suppose that would be clever to ask him first for characterization equipment and what data they provide for each kit and look for some info if it possible.
Judging by the pictures of the VNA they show in the auction, these are complete rubbish.
anything without calibration data are... including those heavily used brand name cal kit many sold in ebay, from accuracy stand point imho. i was to reply long post to the OP describing the pro to Kirkby cal kit, but since he's looking after cheaper option, i decided a short version of a reply. those china ebay just copy pasted Kirkby ads, less custom calibration data and less support service. and remember the china version only provides female or male version not both. Kirkby provides both gender, including throughs, a pen drive containing hand made calibration data with unique serial number to the cal kit and a -3dB verification attenuator, so we can compare the respond plot from calibrated HP8720D compared to our VNA so we know where our VNA stands. as soon we want to purchase a complete set from cheap china matching Kirkby's, the cost will be about the same if not slightly cheaper than. as i simply concluded in earlier post, anything without calibration data will be not much better or worse than a DIY kit. ymmv.Some sellers from China on ebay sell kits with PNA trademark.Judging by the pictures of the VNA they show in the auction, these are complete rubbish.
They wrote in description:
"Accurate electrical models are needed of the opens and short circuits. A number of eBay sellers sell low-cost calibration kits, but these are effectively useless, as they don't have the mathematical models of the opens and shorts necessary to load the constants into a VNA, and we doubt they have optimal phase difference between open and short. This kit is different, in that it is designed, rather than just assembled. With this calibration kit, there is a support page with information on what coefficients to use for Agilent/HP,R/S,ADVANTEST,ANRITSU...".
Price is just 218 USD for SMA kit and looks good generally BUT I'm don't know quality and have no any information about this kits and where to get this calibration data.
I suppose that would be clever to ask him first for characterization equipment and what data they provide for each kit and look for some info if it possible.
anything without calibration data are... including those heavily used brand name cal kit many sold in ebay, from accuracy stand point imho. i was to reply long post to the OP describing the pro to Kirkby cal kit, but since he's looking after cheaper option, i decided a short version of a reply. those china ebay just copy pasted Kirkby ads, less custom calibration data and less support service. and remember the china version only provides female or male version not both. Kirkby provides both gender, including throughs, a pen drive containing hand made calibration data with unique serial number to the cal kit and a -3dB verification attenuator, so we can compare the respond plot from calibrated HP8720D compared to our VNA so we know where our VNA stands. as soon we want to purchase a complete set from cheap china matching Kirkby's, the cost will be about the same if not slightly cheaper than. as i simply concluded in earlier post, anything without calibration data will be not much better or worse than a DIY kit. ymmv.Some sellers from China on ebay sell kits with PNA trademark.Judging by the pictures of the VNA they show in the auction, these are complete rubbish.
They wrote in description:
"Accurate electrical models are needed of the opens and short circuits. A number of eBay sellers sell low-cost calibration kits, but these are effectively useless, as they don't have the mathematical models of the opens and shorts necessary to load the constants into a VNA, and we doubt they have optimal phase difference between open and short. This kit is different, in that it is designed, rather than just assembled. With this calibration kit, there is a support page with information on what coefficients to use for Agilent/HP,R/S,ADVANTEST,ANRITSU...".
Price is just 218 USD for SMA kit and looks good generally BUT I'm don't know quality and have no any information about this kits and where to get this calibration data.
I suppose that would be clever to ask him first for characterization equipment and what data they provide for each kit and look for some info if it possible.
Interesting. That text is copied directly from Dr Kirkby's auction. I wouldn't trust a cal kit from someone willing to copy text like that.
I think it's possible to make a cheap but decent DIY SMA cal kit for use up to maybe 3GHz. I did this many years ago and I still use this cal kit today for many applications. The short and load and open were all DIY using SMA end launchers and I worked out the correction factors myself for the user cal file.
I get very good results with this cal kit and I typically use it to help me model SMD components up to a few GHz.
Once above 3GHz I'd prefer to use a used but decent commercial cal kit, eg a healthy 3.5mm 85033E mechanical cal kit or a 3.5mm Ecal kit. I don't think I'd want to pay $600 for the Kirkby kit. Old/used commercial cal kits can suffer damage and wear so some caution would be needed but I'd still prefer to go down this route compared to a cheapo SMA based alternative no matter how much time and effort went into measuring the cal coefficients.
•Difference between the phase predicted by the mathematical model of the opens, and the actual phase of the opens is <4° from DC to 7 GHzIt would be nice to see some test setup info and some data on this. My first reaction is to run to the hills because this spec of 4 degrees doesn't sound good... maybe I'm misinterpreting what is meant here? .. or maybe it's a typo on the website and the spec is much better than this?
•Difference between the phase predicted by the mathematical model of the shorts, and the actual phase of the shorts is <4° from DC to 7 GHz
An ex colleague of mine bought one of these kits recently and I could maybe try and borrow it and test it. At work, I've got access to new and UKAS calibrated PNA VNAs and various calibrated mechanical kits and several Ecal modules and some £££ Rosenberger test cables. I think the cables cost about £1500 each!
Thanks. I had a quick look over the Kirkby website and there are a few things that give me slight concern.Quote•Difference between the phase predicted by the mathematical model of the opens, and the actual phase of the opens is <4° from DC to 7 GHzIt would be nice to see some test setup info and some data on this. My first reaction is to run to the hills because this spec of 4 degrees doesn't sound good... maybe I'm misinterpreting what is meant here? .. or maybe it's a typo on the website and the spec is much better than this?
•Difference between the phase predicted by the mathematical model of the shorts, and the actual phase of the shorts is <4° from DC to 7 GHz
Also, the kit appears to use regular SMA F-F bullets with the standard screwed at the end. It looks cheap... The closeup images of the short and open don't inspire me. I wouldn't expect a regular SMA bullet to qualify as being part of a VNA cal kit that runs to 7GHz. Maybe these are special versions of the SMA F-F. I'm used to the Suhner ones at work. Also, what happens if the cap rotates? Do you tighten it again with a torque wrench and hope the cal is still good? Maybe it works a lot better than it looks?
A fair proportion of that 4 degrees will be the uncertainties in measuring the actual phase of the standards. According to the datasheet, the 8720D's uncertainty is close to 2 degrees in the 2-8GHz range for a 1.0 reflection coefficient.
You posted up a link to that (fringe) cal coefficient tool using GNU Octave but it looks like it is still being developed.
G0HZUThis would be best done with a youtube video but, sadly, my presentation skills and video making skills are dire so I'm not really the best person for this. You have a fabulous analyser there that is highly capable and there are loads of powerful things you can do with a VNA like that, provided you have a decent cal kit and it is set up properly. I've not used the Kirkby cal kit but I think it's safe to assume its accuracy up to 3GHz will be very good. Good enough for quite serious work. It's the performance of the kit in the 4-7GHz range I'd be unsure about. It might be really good here too but I'd expect it to need some kind of correction polynomial for the type of SHORT it uses.
I know you're an expert on VNAs and you may remember that I bought an 8753E a while back, I also got one of the Kirkby Cal Kits. The truth is that, I never really got to understanding the calibration process properly - I'm a trained RF engineer but have forgotten a lot of things.
I'd like to request that you mentor me and others here to bridge the gaps in our knowledge; if you're willing; perhaps in a new thread or we could do it here?
OK, thanks for the advice. I'm travelling right now but I will try to re-calibrate my VNA and then ask the questions along the lines of - Am I doing it right?
Does anyone here know how long it would take to record all of the relevant calibration coefficients, if someone purchased a open-short-load and sent it to another forum member with access to a good/great VNA?
At the end of the day, when is the modeling necessary? If it's only when you are making your own and trying to improve your design of DIY devices, then we can just bypass that step and send devices to people who can make the measurements for a small fee?
fwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier...
I just wanted to point out these male SMA references available for about $20 in the USA.Amphenol 132360, 132331, 202112 maybe. I have both the kit you linked and these very-cheap three but I'm not knowledgeable enough to say anything except they look very similar.
They manufacturer link goes back to mRS miniVNA Tiny and Pro's website. After more and more searching, it seems like these guys are the manufacturer
Does anyone here know how long it would take to record all of the relevant calibration coefficients, if someone purchased a open-short-load and sent it to another forum member with access to a good/great VNA?
At the end of the day, when is the modeling necessary? If it's only when you are making your own and trying to improve your design of DIY devices, then we can just bypass that step and send devices to people who can make the measurements for a small fee?
Yes the modelling would not be required to transfer a calibration from someone elses' cal kit.
In theory, all you need to do is send them the items you want to use as calibration standards and adapters. They just need to generate an S parameter file for each one on their calibrated VNA.
Then you run it through the script to determine the coefficients. How well that step works is unknown.
If you also sent a decent attenuator then that could be used to compare your new calibration with the calibration of the other user.
So they would need a VNA and a good cal kit. Then they would do a calibration first, and then make 5 or 6 measurements, transfer them to a PC and email them. Then ship back the items.
Deepace KC901V. i'm start to think its a toyish VNA, but i'm not done testing yet.fwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier...He has reduced the IF bandwidth from the default. That would reduce the noise. What VNA have you got?
fwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier, so i know something went wrong. i'm ordering stuffs to further verify my VNA condition if its fits for measurement etc later. i hope they will not get lost during CNY...
The Kirkby Microwave 7 GHz 85033 SMA calibration and verification kit is by far the most popular kit we sell. It can be used to calibrate virtually any network analyzer to enable SMA, 3.5 mm or 2.92 mm coaxial devices to be measured, irrespective of the test ports on the VNA (N, 3.5 mm, APC7, 2.4 mm etc). The connectors on the calibration kit should match the device under test (DUT) and not necessarily the connectors on the VNA. The frequency range of the SMA coaxial calibration kit is from DC to 7 GHz, although higher frequency versions can be built to order.
The kit is both a calibration and verification kit, since it supplied with an attenuator which has been measured on an HP 8720D (20 GHz) VNA using a Agilent 85052B 26.5 GHz 3.5 mm calibration kit. Therefore after setting up the calibration kit, calibrating the VNA, the user can check the VNA is performing properly by measuring the attenuator which is supplied, and comparing that to the measured results, which are on a USB stick supplied with the kit.
By the way... can anybody explain how the "reflection bridge" of the KC901V exactly works?its a power splitter as described by TheSignalPath. there must be detailed explanation, concept and math behind it. i will read them up when i want to make my own diy VNA ;) or if i figure out my VNA is broken and need a tear down. fwiw i guess this type of topology that makes KC901V gives false reading esp impedance value at very low end of frequency 5KHz - 1MHz or so.
I guess it is the structure that looks like a wilkinson power divider?
he claimed he tested all the cal kit sold to me by his own hand. incl the attenuator. so the plot you see should be unique only to my attenuator. i expect other kirkby cal kit owner should have different plot. it took long time (about a week or more) for the calibration to be made, he claimed he do this process in some quantities, to quicken his process. going to lab with my cal kit alone to do the process will take him even longer time, i take and understand this as his economical point of view. furthermore he was not well when i made the purchase i almost cancel the order because it took so long for him that i thought he gave less interest in my order. but i'm glad to support him.Quotefwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier, so i know something went wrong. i'm ordering stuffs to further verify my VNA condition if its fits for measurement etc later. i hope they will not get lost during CNY...Is that attenuator (reference) plot taken with the 8720D VNA and your cal kit? Or is it a 'best' reference taken of the attenuator with the 8720 and a Keysight/Agilent cal kit?
If a calibration kit is made using SMA F-F bullets and end caps there are a few things that will limit its performance. There will be some (extremely tiny) added inductance at the end of the SHORT and also the SMA bullet won't have a perfect 50R Zo. The SMA bullet is about 42ps in terms of delay and this is longer than a regular 85033 cal kit and so this can make any phase variation (due to imperfect 50R Zo) appear slightly worse. The 85033 cal kit uses precision 3.5mm connectors and an air dielectric and it is much better suited for use up at 7GHz.i'm not sure how to reply to this, just as how i'm going to reply to Kirkby in my last test, i'm not knowledgable much that i need to gain some info, do some test (or even need to have access to much expensive gears) to be able to comprehend some of the meaning. i only can hope or rely on some expert to do the testing and give some promise that it should work.
It doesn't take much to get 4 degrees of phase error over 6GHz in a DIY cal kit. If you get several degrees of phase error and it isn't corrected for by the cal kit corrections then you can expect to see that reference plot degrade a lot by 5GHz and it will get quite noisy by 7GHz. Also, an inline test of a 3dB attenuator isn't a very critical test.
However, I see this process as polishing a turd once you get up to 7GHz. Much better to have a decent 85033 cal kit here.that Agilent cal kit if well within spec and in full complete data, should be about 2-3X the cost of my VNA. i can see used price is $2K already without any data. i would not give my money betting on that. ps: i'm not sure why Kirkby called his cal kit as 85033E similar to agilent naming. maybe its tracable to the agilent cal kit he owned? and his cal kit is modelled/compared after that? i'm not sure.
I entered a polynomial for the Lx corrections for my DIY cal kit SHORT and got the result below...what i concluded from your reply #35 and #36 is, are you suggesting that using less quality cal kit in the same VNA will result in more ripple? if that is the case, there is possibility that kirkby did the attenuator report using agilent cal kit as his calibration standard? i'll need to confirm this back to him.
"Less quality cal kit" - Dr. Dunsmore of HP/Agilent/Keysight, the 8753 designer, was saying he could calibrate a VNA using a brick, as long as the brick is accurately characterized with calibration coefficients.
what i concluded from your reply #35 and #36 is, are you suggesting that using less quality cal kit in the same VNA will result in more ripple? if that is the case, there is possibility that kirkby did the attenuator report using agilent cal kit as his calibration standard? i'll need to confirm this back to him.For sure you will get more ripple with an inferior cal kit or with one that has not been corrected properly. I can make my ENA VNA look REALLY bad if I deliberately use a poor cal kit.
Can you post up your Kirkby cal kit correction file or list its corrections for Cx and delay etc?maybe the attached file is what you looking for. its for agilent VNA if using my cal kit with them. its not relevant to my VNA though.. fwiw...
Note also that I'm just doing this in my workroom at home and using an RF simulator to create the comparison model.what rf simulator? is this simulator accessible to mortal? ;D can i learn? ... for the rest of your post, i need time understanding that...
I think your problems may be due to the type of VNA you are using. I've not seen one of those models before and it may have quite poor performance.now isnt that golden? (from your link above http://www.kirkbymicrowave.co.uk/support/Kits/85033/ (http://www.kirkbymicrowave.co.uk/support/Kits/85033/))
...
The results for the short aren't as good because there aren't any Lx corrections in the data. But it is still good considering it is using SMA based connectors in the SHORT. It would be easy to correct this for VNAs that support Lx coefficients and if a VNA supports this feature then I guess these would be included in the data?i cant see any inductance effect for SHORT in any kirkby calibration data including the master file from where everything else are derived. so i guess his measurement setup is not supporting that, or consider the effect negligible. albeit not perfect, i can say ±0.5 degree error is good enough for me i guess (my VNA systematic error will be much worse from what i figured out so far). thanks for all your reports and findings..
Probably the most controlled way to try your experiment is to see if you can generate Cx coefficients for the Kirkby kit OPEN s1p file posted below. Then post up your Cx values here and I'll see how they perform in terms of flattening the phase? Will I see the same flat result as in post #47 for example?
Probably the most controlled way to try your experiment is to see if you can generate Cx coefficients for the Kirkby kit OPEN s1p file posted below. Then post up your Cx values here and I'll see how they perform in terms of flattening the phase? Will I see the same flat result as in post #47 for example?
1st optimization ended with status: Optimization stopped because xtol_rel or xtol_abs was reached. (NLOPT_XTOL_REACHED)
2nd optimization ended with status: Generic success return value. (NLOPT_SUCCESS)
Optimization results:
offs_delay = 50.000000 ps
offs_loss = 5.000000 Gohm/s
offs_Z0 = 50.000000 ohm
C0 = -172.920826 * 1e-15 F
C1 = 10000.000000 * 1e-27 F/Hz
C2 = -1238.347686 * 1e-36 F/Hz^2
C3 = 19.888550 * 1e-45 F/Hz^3
Residual RMS error : -47.880563 dB
?1st optimization ended with status: Optimization stopped because xtol_rel or xtol_abs was reached. (NLOPT_XTOL_REACHED)
2nd optimization ended with status: Generic success return value. (NLOPT_SUCCESS)
Optimization results:
offs_delay = 55.447558 ps
offs_loss = 5.000000 Gohm/s
offs_Z0 = 50.000000 ohm
C0 = -265.965357 * 1e-15 F
C1 = -2793.805192 * 1e-27 F/Hz
C2 = 1240.335578 * 1e-36 F/Hz^2
C3 = -194.306089 * 1e-45 F/Hz^3
Residual RMS error : -53.982524 dB
Optimization results:
offs_delay = 55.465329 ps
offs_loss = 5.685029 Gohm/s
offs_Z0 = 49.172627 ohm
C0 = -286.232017 * 1e-15 F
C1 = -2372.098441 * 1e-27 F/Hz
C2 = 1891.981433 * 1e-36 F/Hz^2
C3 = -246.050762 * 1e-45 F/Hz^3
Residual RMS error : -62.879680 dB
The last two look the best but I'm not sure if I'm modelling the offset Zo correctly. I found that tweaking Zo improved the male SHORT Kirkby kit and that was the thing I would have experimented with if I had this kit here as per post #53.
Are you optimising to 3GHz or 6GHz? Your data looks flat to 3GHz but there is a tiny slope up to 6GHz. But it still looks good.
However, some of your values look strange. Normally the fringing capacitance is about 50fF but your optimiser has put in a negative capacitance of -286fF. I guess that will still be OK in the world of mathematics but can you set realistic limits for this capacitance of maybe 30fF to 100fF and run it again?
On the Agilent kit this capacitance only varies by a tiny amount away from 50fF across frequency.
Female open. (Use OPEN(M) or OPEN -F- depending on model of VNA - see notes above) **
Minimum frequency: 0 GHz
Maximum frequency: 7.0 GHz
Offset Zo: 50.0 ohms
Offset loss: 3.0 G ohm/s
Offset delay: 39.8 ps
C0: 44.36
C1: 156.42
C2: 1159.1
C3: -131.92
Here's what appears to be the custom coefficients for that Kirkby female OPEN and C0 looks to be about 44fF.QuoteFemale open. (Use OPEN(M) or OPEN -F- depending on model of VNA - see notes above) **
Minimum frequency: 0 GHz
Maximum frequency: 7.0 GHz
Offset Zo: 50.0 ohms
Offset loss: 3.0 G ohm/s
Offset delay: 39.8 ps
C0: 44.36
C1: 156.42
C2: 1159.1
C3: -131.92
I just spotted your attached results files.
The optimiser tool you are using looks very powerful. I tried downloading it and the other sparam tool etc and I already have GNU Octave but I wasn't sure what to type in the command line. I tried an edited version of the default example but it didn't like it. I'm a newbie with GNU Octave so I probably haven't installed something correctly. I assume all the plots come from this optimiser tool?
Try running it up to 6GHz or maybe 7GHz as Fmax. It might give a flatter result?
Optimization results:
offs_delay = 35.951981 ps
offs_loss = 10.000000 Gohm/s
offs_Z0 = 49.000000 ohm
C0 = 100.000000 * 1e-15 F
C1 = 99.011405 * 1e-27 F/Hz
C2 = 30.000000 * 1e-36 F/Hz^2
C3 = 30.000000 * 1e-45 F/Hz^3
Residual RMS error : -22.299742 dB
Yes, that looks bad at the top end. The 30.0000 values look suspicious. Has this hit a limit?
I don't think you need to alter Zo away from 50R on this OPEN because DrKirkby managed to get a really flat line with Z0 = 50 in my earlier post.
Can you try locking in some of his values and see if it works better with fewer variables? I'm off to bed soon so can't do much more tonight...
Optimization results:
offs_delay = 52.360635 ps
offs_loss = 5.470724 Gohm/s
offs_Z0 = 49.000012 ohm
C0 = -226.929303 * 1e-15 F
C1 = -1964.414279 * 1e-27 F/Hz
C2 = 2232.392337 * 1e-36 F/Hz^2
C3 = -236.119457 * 1e-45 F/Hz^3
Residual RMS error : -67.897497 dB
Optimization results:
offs_delay = 34.432636 ps
offs_loss = 5.643170 Gohm/s
offs_Z0 = 49.000000 ohm
C0 = 138.424072 * 1e-15 F
C1 = -1291.076067 * 1e-27 F/Hz
C2 = 2442.710614 * 1e-36 F/Hz^2
C3 = -217.883669 * 1e-45 F/Hz^3
Residual RMS error : -67.731741 dB
[code]
Also, I just realised that METAS VNA Tools II tool you are using is free. :-+but i need to email someone to get the download link. if click the download link, setupping outlook will popup |O i just tried copy paste the email address into yahoo mail.
I've attached the output pdfs for a couple of new graphs I added to the script. These show the difference between the model and the s1p file and I think these are comparable to what G0HZU shows in post #47.Yes, your data looks much better now.
Also, I just realised that METAS VNA Tools II tool you are using is free. :-+but i need to email someone to get the download link. if click the download link, setupping outlook will popup |O i just tried copy paste the email address into yahoo mail.
...No reply yet. Cutting them some slack though because its free after all and it looks really handy.
They might have their hands full if all the VNA nuts on here start registering en masse.
QuoteI've attached the output pdfs for a couple of new graphs I added to the script. These show the difference between the model and the s1p file and I think these are comparable to what G0HZU shows in post #47.Yes, your data looks much better now.
That METAS VNA tool used by suj looks to be very powerful. With my simulator I had a go at plotting the fringing capacitance of the Agilent/Keysight 85033 OPEN vs frequency and I think it looks like the plot below. I hope I've got this right. It only changes a small amount and these corrections only really affect the flatness above about 5GHz.
With a cheapo SMA cal kit like the Kirkby kit the SMA based standards won't have the same design integrity as a proper 3.5mm kit so the corrections are much more important because they have to correct for the flaws over most of their 7GHz range. The male SHORT in the Kirkby kit does not look good at all with its limited corrections. I couldn't live with it unless it was corrected better in the cal kit file.
...No reply yet. Cutting them some slack though because its free after all and it looks really handy.
They might have their hands full if all the VNA nuts on here start registering en masse.
I think you don't have a reply because today is Sunday and the institute is not working today 8). I didn't wait for the link too long.
Male short. (Use SHORT(F) or SHORT -M- depending on model of VNA - see notes above) **
Minimum frequency: 0 GHz
Maximum frequency: 7.0 GHz
Offset Zo: 50.0 ohms
Offset loss: 3.0 G ohm/s
Offset delay: 57.997 ps
If you haven't downloaded it already here is the bundled s1p custom data on the Kirkby male SHORT in a text file and I've listed the custom corrections below.QuoteMale short. (Use SHORT(F) or SHORT -M- depending on model of VNA - see notes above) **
Minimum frequency: 0 GHz
Maximum frequency: 7.0 GHz
Offset Zo: 50.0 ohms
Offset loss: 3.0 G ohm/s
Offset delay: 57.997 ps
There is only a delay correction and I get the phase response below. This does not look good but I guess the male part of the kit will be used less often. The older 8753 VNAs kind of default to 'insertable device' calibrations so they would often use both male and female kits for a full two port calibration. In this case it's debateable if the Kirkby kit is 'fit for purpose' for a decent 6GHz lab VNA like an 8753?
offs_delay = 54.877614 ps
offs_loss = 2.058719 Gohm/s
offs_Z0 = 51.050105 ohm
L0 = -3687.287669 * 1e-12 H
L1 = 10000.000000 * 1e-24 H/Hz
L2 = -978.814153 * 1e-33 H/Hz^2
L3 = 2713.293761 * 1e-42 H/Hz^3
Residual RMS error : -48.553224 dB
How does it look if you try and optimise it with METAS? It looks better with just a Zo tweak but maybe also try it with Lx corrections.
...It's a shame this Lx correction can't be added to the 8753 firmware in some way.
...It's a shame this Lx correction can't be added to the 8753 firmware in some way.
By the way. It should be possible to do it off-line with Metas. It has a built-in driver for the 8753 and 8720 series (as well as 8510C, ENA, PNA). You can make measurements and off-line error correction using this software. Definitions of the "short" element that you can prepare have the option of defining L.
The procedure is shown in the tutorial on the program's website.
It looks like a Swiss army knife ::)
By the way. It should be possible to do it off-line with Metas.Wow, that sounds great. I hope to get a copy of METAS soon :)
Optimization results:
offs_delay = 32.331122 ps
offs_loss = 6.333923 Gohm/s
offs_Z0 = 60.858025 ohm
L0 = 872.429450 * 1e-12 H
L1 = 5981.654164 * 1e-24 H/Hz
L2 = 37028.127991 * 1e-33 H/Hz^2
L3 = 3160.750516 * 1e-42 H/Hz^3
Residual RMS error : -53.679006 dB
QuoteBy the way. It should be possible to do it off-line with Metas.Wow, that sounds great. I hope to get a copy of METAS soon :)
See below for a quick and dirty OPEN and SHORT made from a pair of SMA F-F bullets. One has a commercial SC end cap for the short. Sadly, the two bullets are from different manufacturers so they are not going to be the same but the end cap for the short is a known part and it isn't expensive. Maybe $9?
So maybe if I buy some Amphenol SMA F-F bullets from Farnell ($8 ea?) we could have a go at making a cheap cal kit for the masses?
But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below?
But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below?
Agilent Definition
Standard Type: Open
Offset Z0 (Ohm): 60.711892
Offset Delay (ps): 27.289762
Offset Loss (GOhm/s): 3.507799
C0 (E-15 F): 414.232256
C1 (E-27 F/Hz): -6871.633507
C2 (E-36 F/Hz^2): -4959.099088
C3 (E-45 F/Hz^3): 470.623016
Agilent Fit Error
RMS Error
0.001900
Max Error
0.003349
_______________________________________________
Agilent Definition
Standard Type: Open
Offset Z0 (Ohm): 50.000000
Offset Delay (ps): 58.437897
Offset Loss (GOhm/s): 2.711473
C0 (E-15 F): -304.566047
C1 (E-27 F/Hz): -8873.121112
C2 (E-36 F/Hz^2): 2622.781977
C3 (E-45 F/Hz^3): -343.691735
Agilent Fit Error
RMS Error
0.002197
Max Error
0.003648
_______________________________________________
Agilent Definition
Standard Type: Short
Offset Z0 (Ohm): 56.059063
Offset Delay (ps): 41.557996
Offset Loss (GOhm/s): 3.717653
L0 (E-12 H): -222.842514
L1 (E-24 H/Hz): -19759.249841
L2 (E-33 H/Hz^2): 11091.105982
L3 (E-42 H/Hz^3): -651.849387
Agilent Fit Error
RMS Error
0.001378
Max Error
0.003844
_______________________________________________
Agilent Definition
Standard Type: Short
Offset Z0 (Ohm): 50.000000
Offset Delay (ps): 32.074189
Offset Loss (GOhm/s): 4.973737
L0 (E-12 H): 492.787861
L1 (E-24 H/Hz): -6736.857074
L2 (E-33 H/Hz^2): -3868.927304
L3 (E-42 H/Hz^3): 506.666193
Agilent Fit Error
RMS Error
0.001556
Max Error
0.004609
Also, if the cal is done offline in software, then changing coefficients (i.e. recalibrating using a different set of coefficents) is purely software and doesn't require another sweep. So it would be technically possible to do a full sweep and change cal definitions on the fly.That would be neat, I'd definitely be interested in being able to do this. My original DIY SMA kit must be about 12 years old now and it would be nice to retweak the corrections for any wear. I spent ages optimising the cal kit for it when I first got my HP8714B VNA and this involved lots of repetitive tests and calibrations. I don't really want to do this the hard way again.
Then I found a bug in the model calculation for the Lx params. Fixed that and tada, now it lines up :)
Then I found a bug in the model calculation for the Lx params. Fixed that and tada, now it lines up :)
:-[ uh, oh, you mean the indices of the Lx coefficients were off by 1in the std_model_s_params() function, right? I'll upload a corrected version shortly, thanks!
Also, if the cal is done offline in software, then changing coefficients (i.e. recalibrating using a different set of coefficents) is purely software and doesn't require another sweep. So it would be technically possible to do a full sweep and change cal definitions on the fly. The definitions would match the real cal standards very closely.
Also, if the cal is done offline in software, then changing coefficients (i.e. recalibrating using a different set of coefficents) is purely software and doesn't require another sweep. So it would be technically possible to do a full sweep and change cal definitions on the fly. The definitions would match the real cal standards very closely.
If you have a VNA where you can access to the calibration coefficients, like the 8753 and, I think, most of the ones not targeted at hobbyists, you can simply use something like scikit-rf to do the calibration using the calkit S parameters directly (no need of building any model of them) and then write the computed calibration coefficients back to the VNA. I don't know if this is what the METAS VNA Tools can actually do or if it allows only a post processing of raw data acquired from the VNA.
Then another issue is the calkit repeatability, with cheap stuff you never know how it will behave tomorrow :)
Also, the proposal I mentioned a while back, was to not use an open standard at all when the VNA has a female SMA port.
QuoteAlso, the proposal I mentioned a while back, was to not use an open standard at all when the VNA has a female SMA port.
I've done that with a known SMA barrel at the end of an SMA cable and I have a very 'short' male SHORT made from a cut down Suhner (good quality) SMA connector. See the image below.
It is possible to just use an SMA end cap for the short instead but the end cap will obviously spin as it is being undone so this can cause wear. The short below has a nut that can still spin (so no wear issues) but this means it has some delay in it and the performance isn't great and I don't use this very often and I try to only use it below 1GHz.
I entered a polynomial for the Lx corrections for my DIY cal kit SHORT and got the result below...what i concluded from your reply #35 and #36 is, are you suggesting that using less quality cal kit in the same VNA will result in more ripple? if that is the case, there is possibility that kirkby did the attenuator report using agilent cal kit as his calibration standard? i'll need to confirm this back to him.
anyway i'm doing the test with cheap crap china sma connection and 50 ohm coax cable. maybe those also contributes to the rippling effect, i'm not sure. what i'm sure is the cabling still give consistent result even if i move them around a little bit... fwiw...
* The Dr Kirkby data and method you have to use (i.e. using the terminator) don't seem to line up with what he has in his FAQ: http://www.kirkbymicrowave.co.uk/FAQ/How-do-I-verify-the-calibration-kit-is-working-properly/ (http://www.kirkbymicrowave.co.uk/FAQ/How-do-I-verify-the-calibration-kit-is-working-properly/)i did exactly according to that in my first report to him (see attached version 1 report fwiw). the S11 or S22 (just turning the attenuator upside down on the same VNA port 1) was totally out. in our email conversation he admitted the mistake of procedure in his link and said he will edit the link, but it seems he havent. he asked me to do the test again with attenuator terminated. with attenuator's end dangling opened (like in the link), the reflection from opened end will affect to the port under test on the under end, something like that according to him.
* The S21 measurements are probably poor as the Deepace doesn't seem to support a 'full 2 port' calibration. Do you know if it supports a full 2 port calibration, or is it just a 'response' calibration? In The Signal Path youtube review it shows a simple response cal only with a through.correct, there is no directional coupler (or power splitter) on the other port 2 of the VNA, so it can measure S21 only but not true S12. i have to turn the DUT around to simulate S12. i guess the VNA will try to solve half part of the full 4 port parameter matrix.
* A full 2 port cal can correct for many more errors than a simple response cal can. Since you are using a lower cost, compact device which doesn't have great directivity and port return loss, then you will really need this error correction to get decent results on the S21 test.
* If you can pull the raw data out of the device and get it into touchstone format, then you should be able to use scikit-rf or Metas to do the full 2 port cal.what raw data? sorry noob question. but i dont think i can extract anything from the device other than its measurement result.
* According the manual it supports using an external bridge/coupler. Sometimes high quality ones come up on eBay which have come from HP gear.thanks for reminding me this. i will study more on this.
* The Dr Kirkby data and method you have to use (i.e. using the terminator) don't seem to line up with what he has in his FAQ: http://www.kirkbymicrowave.co.uk/FAQ/How-do-I-verify-the-calibration-kit-is-working-properly/ (http://www.kirkbymicrowave.co.uk/FAQ/How-do-I-verify-the-calibration-kit-is-working-properly/)i did exactly according to that in my first report to him (see attached version 1 report fwiw). the S11 or S22 (just turning the attenuator upside down on the same VNA port 1) was totally out. in our email conversation he admitted the mistake of procedure in his link and said he will edit the link, but it seems he havent. he asked me to do the test again with attenuator terminated. with attenuator's end dangling opened (like in the link), the reflection from opened end will affect to the port under test on the under end, something like that according to him.
* The S21 measurements are probably poor as the Deepace doesn't seem to support a 'full 2 port' calibration. Do you know if it supports a full 2 port calibration, or is it just a 'response' calibration? In The Signal Path youtube review it shows a simple response cal only with a through.correct, there is no directional coupler (or power splitter) on the other port 2 of the VNA, so it can measure S21 only but not true S12. i have to turn the DUT around to simulate S12. i guess the VNA will try to solve half part of the full 4 port parameter matrix.
* A full 2 port cal can correct for many more errors than a simple response cal can. Since you are using a lower cost, compact device which doesn't have great directivity and port return loss, then you will really need this error correction to get decent results on the S21 test.
* If you can pull the raw data out of the device and get it into touchstone format, then you should be able to use scikit-rf or Metas to do the full 2 port cal.what raw data? sorry noob question. but i dont think i can extract anything from the device other than its measurement result.
That's why i hope somebody can recommend an alternative.
That's why i hope somebody can recommend an alternative.
There is a description about using Rosenberger parts, similar to the ones in the SDR-Kits, as calkit, see http://www.hhft.de/index.php?page=competences&subpage=calibration (http://www.hhft.de/index.php?page=competences&subpage=calibration). They just use the offset lengths to describe the standards and leave all the Cx and Lx to zero. It may not be so important to split the femtofarad if you go up to 5 GHz - any excess capacitance or inductance can probably taken into account by adjusting the offset length only.
Not sure if you have seen this info :- SDR kits actually publish reasonable delay info, and the part numbers of the Rosenberger parts they use. It used to be really difficult to find on their old website but its better now. There is also a document explaining how they got those values. Unfortunately they don't provide the s1p/s2p files or we could use them with your script to get the missing info.
Not sure if you have seen this info :- SDR kits actually publish reasonable delay info, and the part numbers of the Rosenberger parts they use. It used to be really difficult to find on their old website but its better now. There is also a document explaining how they got those values. Unfortunately they don't provide the s1p/s2p files or we could use them with your script to get the missing info.
yes, I should have started my message saying "in addition to the well know calkit from SDR-Kits, which comes wit some modeling data" :) .
A few years ago I exchanged a couple of emails with Kurt Poulsen (which prepared the SDR-Kits calkit docs), when I saw a message he posted to the VNWA Users Group on Yahoo saying that had measured the S-parameters of the Amphenol Connex and Rosenberger calibration kits; I don't remember if he also sent me the related .s1p/.s2p files, need to check my old emails.
Anyway, it would make sense to tell the SDR-Kits people that making the measured calkit data available may help in selling more kits :) .
If you extract the data then you can still do better using scikit-rf. It supports a calibration type called 'Two Port one Path' or something like that. Basically you can do a full 2 port cal with only one directional coupler. You do need to swap around the DUT to measure both ports.i think this is the missing piece for me to all of your discussions here, thanks i'll try to catch up. but the downloaded META VNA Tools II only works on Windows later than Vista, so my WinXP cant installed, another |O moment... i'll try install it in another Win10 PC.
However to do this, first you need to be able to extract the raw data for the sweeps and transfer it to a PC. Then use software on the PC to do the calibration instead of using the software inside the KC901V.
Without doing a cal of the device, you do a sweep of your cal standards, and export them each into different files - i.e. short.s1p, open.s1p, load.s1p, thru.s1p and the device you want to test dut.s1p. Then you should be able to use those files containing 'raw data' with software like scikit-rf or Metas to do a calibration and measure the device on your PC.
Check the 'Data Saving' section of the manual. I found it online, apparently you can export s1p data files to an SD card in the smith chart mode.correct. i'll study this more seriously when i got installed any VNA tools. thanks.
If you extract the data then you can still do better using scikit-rf. It supports a calibration type called 'Two Port one Path' or something like that. Basically you can do a full 2 port cal with only one directional coupler. You do need to swap around the DUT to measure both ports.i think this is the missing piece for me to all of your discussions here, thanks i'll try to catch up. but the downloaded META VNA Tools II only works on Windows later than Vista, so my WinXP cant installed, another |O moment... i'll try install it in another Win10 PC.
However to do this, first you need to be able to extract the raw data for the sweeps and transfer it to a PC. Then use software on the PC to do the calibration instead of using the software inside the KC901V.
Without doing a cal of the device, you do a sweep of your cal standards, and export them each into different files - i.e. short.s1p, open.s1p, load.s1p, thru.s1p and the device you want to test dut.s1p. Then you should be able to use those files containing 'raw data' with software like scikit-rf or Metas to do a calibration and measure the device on your PC.Check the 'Data Saving' section of the manual. I found it online, apparently you can export s1p data files to an SD card in the smith chart mode.correct. i'll study this more seriously when i got installed any VNA tools. thanks.
scikit-rf is a much more techy to get installed and working, but has more flexibility so I will use that for experimentation.i am heavy butt lazy arse nowadays that i expect a ready made exe, i dont have much more time for long step by step install of Anaconda, Phyton learning etc. but i'll try that if i cant work out META... thanks.
scikit-rf is a much more techy to get installed and working, but has more flexibility so I will use that for experimentation.i am heavy butt lazy arse nowadays that i expect a ready made exe, i dont have much more time for long step by step install of Anaconda, Phyton learning etc. but i'll try that if i cant work out META... thanks.
In other news, on his Test Equipment group Dr Kirkby offered a couple of out of spec cal kits at a low price.
Since these come with s-params I grabbed one of them. Shipping is very high, but ultimately still worth it for me to have items which I can use as a calibrated reference.
https://groups.io/g/Test-Equipment-For-Sale-Wanted-or-Exchange
In other news, on his Test Equipment group Dr Kirkby offered a couple of out of spec cal kits at a low price.
Since these come with s-params I grabbed one of them. Shipping is very high, but ultimately still worth it for me to have items which I can use as a calibrated reference.
https://groups.io/g/Test-Equipment-For-Sale-Wanted-or-Exchange
The question is, did you pay soon enough to get one of the sets. I know I paid for one 14 hours ago.
Congratulation for your score. When i made the purchase, i wish i can have yellow case instead of black. But i choosed cheaper option of 'whatever color mostly in stock'. In the end i got... yellow case ;D
Since these come with s-params I grabbed one of them. Shipping is very high, but ultimately still worth it for me to have items which I can use as a calibrated reference.
QuoteSince these come with s-params I grabbed one of them. Shipping is very high, but ultimately still worth it for me to have items which I can use as a calibrated reference.
I'm not convinced you can treat the Kirkby kit as some form of calibrated reference if you want to start playing with Cx and Lx factors. I'm not an expert on SMA-SMA connector variability but you can't avoid having a subtle discontinuity between your SMA test cable and the Kirkby SMA cal connector because you can't expect two solid dielectric connections to mate perfectly without a tiny (uncontrolled) air gap and without some form of pin mating variability as well. So I don't know how much this will affect the phase response across a 6GHz bandwidth. A 3.5mm to SMA connection should be a lot better in this respect.
Also, an SMA female inner expands as it is mated so the Zo (subtly) changes depending on mating depth and male pin diameter. The 3.5mm connector has a solid outer so this problem goes away.
I just think that once you get past 2 or 3GHz you reach the point where you are trying to polish a turd if you want to try and 'calibrate' an SMA based standard using Cx and Lx corrections.
I've always had decent results with my DIY female SMA cal kit but this was only up to the 3GHz limit of my old HP8714B VNA. Also, a lot depends on how accurate it all really needs to be. I suspect that you can get away with using an SMA based cal kit up to 7GHz if you just want to make casual measurements and can accept a lot of uncertainty.
Has anyone tried doing an 'insertable device' calibration using both the male and female parts of the Kirby kit up to 7GHz and them done some critical tests? Even the basic 6dB attenuator test would be interesting to see.
OK I found it at work today. I had to walk 1km into a horizontal blizzard to get it as it was being used at another company site :)
It's a 3.5mm F-F connector but not the same grade as the 3.5mm connectors in a typical Agilent cal kit as it uses expanding female contacts rather than the delicate solid centre (with inner petals) as per an Agilent cal kit. So it might not be that much better than an SMA F-F connector, especially as this one is very old and probably quite worn. But I've cleaned it and I'll try it later today. It's really cold and snowy here in the UK and we've been sent home from work early today and told that we don't have to go back until Monday :)
I'll have an initial look at this connector once my VNA has warmed up.
My very budget Kirkby kit - I added the USB drive and Pelican case. I will be buying a good quality female - female and a male to male.
My very budget Kirkby kit - I added the USB drive and Pelican case. I will be buying a good quality female - female and a male to male.
Nice one :-+
I didn't go for the case or the usb stick. I did get the attenuator and the thru's though.
Mine is still some way away though. I really should use the time to build a case :)
When I say I added the USB drive and Pelican case I was meaning I added it myself. I already had an extra Pelican 1020 sitting here, same as Dave uses.did the cal kit comes with calibration data? if not, how are you going to calibrate it?
When I say I added the USB drive and Pelican case I was meaning I added it myself. I already had an extra Pelican 1020 sitting here, same as Dave uses.did the cal kit comes with calibration data? if not, how are you going to calibrate it?
When I say I added the USB drive and Pelican case I was meaning I added it myself. I already had an extra Pelican 1020 sitting here, same as Dave uses.did the cal kit comes with calibration data? if not, how are you going to calibrate it?
Dr Kirkby is emailing me the file for my specific kit to load into my FieldFox.
When I say I added the USB drive and Pelican case I was meaning I added it myself. I already had an extra Pelican 1020 sitting here, same as Dave uses.did the cal kit comes with calibration data? if not, how are you going to calibrate it?
Dr Kirkby is emailing me the file for my specific kit to load into my FieldFox.
When you get the s1p files, can you post them please? I would like to compare them with mine when it arrives.
Also, out of interest which type of through calibration did you use for the attenuator pics?
(1000th post whoop whoop!)
...during the full 2 port SOLT calibration...
...Simply normalized the system...
The poor plots were blamed on poor phase stability so I assumed some form of SOLT calibration had been done. What's the point of posting up the attenuator plot if it wasn't made with the Kirkby cal kit? I'm lost...
I also don't see the point of posting up a plot to 6GHz using poor cables and a normalisation. The mismatch uncertainty during the through cal ought to be the main problem, not phase stability. Maybe try it again using attenuators at the cable ends during the thru cal. This will improve the port match.
The poor plots were blamed on poor phase stability so I assumed some form of SOLT calibration had been done. What's the point of posting up the attenuator plot if it wasn't made with the Kirkby cal kit? I'm lost...
I also don't see the point of posting up a plot to 6GHz using poor cables and a normalisation. The mismatch uncertainty during the through cal ought to be the main problem, not phase stability. Maybe try it again using attenuators at the cable ends during the thru cal. This will improve the port match.
It is fair you are lost. The post was largely irrelevant, just got caught up playing with my toys, sorry guys.
As far as a cal goes for S21 the only cal option I have is to normalize. The FF I have does not do S12/S22 nor phase with S21.
I can do the full OSL for S11 of course.
With respect to the attenuation plots it is quite easy for me to shift the plots around by moving the cable, I did switch to another which isn't as sensitive but it is still easy to see changes.
edit - G0HZU - the plot you made looks great. Do you know what(if any) kind of averaging or smoothing your analyzer is doing?RBW is 1kHz and averaging and smoothing both set to off.
Next, i start a "S11 1-Port" calibration.
When selecting "OPENS", a new menue appears and asks me for "OPEN (M)" or "OPEN (F)".
Since i am using the female-open, i guess selecting "OPEN (F)" is correct here?
Ok, so after i finalize the calibration by pressing "DONE 1-PORT CAL", i set the VAN to Smith-chart to verify if calibration is correct.
I do this by attaching the SHORT again and check if the Smith-chart gives me a point at the short-position.
However, i don't get a dot at the short position but a line reaching from short to almost infinit on the upper, outer pure inductor circle.
Similar, just mirrored is displayed when the OPEN reference is connected.
For compensation, i applied a port extension of 58.14 ps and get the expected results (dots) with all 3 calibration standards.
Ok, so after i finalize the calibration by pressing "DONE 1-PORT CAL", i set the VAN to Smith-chart to verify if calibration is correct.
I do this by attaching the SHORT again and check if the Smith-chart gives me a point at the short-position.
However, i don't get a dot at the short position but a line reaching from short to almost infinit on the upper, outer pure inductor circle.
Similar, just mirrored is displayed when the OPEN reference is connected.
For compensation, i applied a port extension of 58.14 ps and get the expected results (dots) with all 3 calibration standards.
I thought that with the complete calibration data on the floppy disk, there would be no need for manual port extension entry?
Another thing that irritates me is that the 50 Ohm references are 49,5 and 51,1 Ohm instead of "50,0".
I would expect to get better quality references for that price?
Don't forget that your cal kit SHORT and OPEN is at the far end of either a male-male SMA adaptor or a female SMA adaptor. The typical delay in the F-F adaptor is about 42ps and the M-M is probably about 58ps.
So the moment you put your cal kit OPEN back on the VNA after a calibration the open end of your OPEN will be either 42ps or 58ps away from your reference plane. So the smith chart on the VNA will show a 0-6GHz line going maybe halfway around the smith chart. It's effectively measuring the SMA F-F barrel.
My guess is that you have tried to do a 1 port calibration and told the VNA the wrong gender for the cal kit. So the 42ps and 58ps are muddled. Try again for the 42ps female OPEN (and don't forget the VNA refers to this as OPEN (M) ) and it might look like this:
** Male load. **
Minimum frequency: 0 MHz
Maximum frequency: 7000 MHz
Offset Zo: 50.0 ohms
Offset loss: 1000 Mohm/s
Offset delay: 0 ps
** Female load. **
Minimum frequency: 0 MHz
Maximum frequency: 7000 MHz
Offset Zo: 50.0 ohms
Offset loss: 3000 Mohm/s
Offset delay: 0 ps
Some sellers from China on ebay sell kits with PNA trademark.
They wrote in description:
"Accurate electrical models are needed of the opens and short circuits. A number of eBay sellers sell low-cost calibration kits, but these are effectively useless, as they don't have the mathematical models of the opens and shorts necessary to load the constants into a VNA, and we doubt they have optimal phase difference between open and short. This kit is different, in that it is designed, rather than just assembled. With this calibration kit, there is a support page with information on what coefficients to use for Agilent/HP,R/S,ADVANTEST,ANRITSU...".
I could need some advice on what i am doing wrong with my Kirkby cal-kit.
(Please appologise stupid questions, since VNA measurements are totally new to me ;) )
My setup consists of:
-) HP 8753E VNA (6 GHz)
-) Kirkby 85033 SMA calkit
-) 50 cm RG316D koax
I followed the instructions on the Kirkby 8753 page here: http://www.kirkbymicrowave.co.uk/support/VNAs/HP-Agilent-Keysight/8753/ (http://www.kirkbymicrowave.co.uk/support/VNAs/HP-Agilent-Keysight/8753/)
On the floppy disk there are 3 files (SMA, SMA_M_M, SMA_F_F).
I selected "SMA" and loaded it with "RECALL STATE".
Is that the correct file to choose?
After that, the frequency range is automatically changed to 300 kHz ... 3 GHz.
Shouldn't it be set to the full range of 30 kHz - 6 GHz of my VNA?
I could need some advice on what i am doing wrong with my Kirkby cal-kit.
(Please appologise stupid questions, since VNA measurements are totally new to me
On the floppy disk there are 3 files (SMA, SMA_M_M, SMA_F_F).
I selected "SMA" and loaded it with "RECALL STATE".
Is that the correct file to choose?
After that, the frequency range is automatically changed to 300 kHz ... 3 GHz.
Shouldn't it be set to the full range of 30 kHz - 6 GHz of my VNA?
P.S.:
Another thing that irritates me is that the 50 Ohm references are 49,5 and 51,1 Ohm instead of "50,0".
I would expect to get better quality references for that price?
What we care about is the RF performance of the kit. If the loads were made from wirewound resistors, as standard resistors usually are, the DC resistance could be made very close to 50 ohms, but the RF performance would be appalling.
You might note there's no specification for the DC resistance of RF terminations in any of the Keysight calibration kits, nor in the loads from companies like Minicircuits. It really is irrelevant.
Here's an old plot of my Suhner 18GHz SMA load showing the LF performance. This load was hand selected from a large batch of identical Suhner 18GHz loads to be the closest to 50R and I just measured it again this evening (after many years) and it is 49.99R at DC on a Keithley 2000 4W meter.
This plot was taken at work (a few years ago) using an 85033E cal kit and the VNA was a 6GHz 8753ES. It shows very close agreement with 50R all the way up to 200MHz. So this implies the 8753ES/85033E can measure a real 50R quite accurately.
On my VNA here at home (using my N4431B-60006 Ecal to calibrate the VNA) the same Suhner 18GHz load measures 49.94R at LF. So pretty close to 50R again!
I also dug out another Suhner 18GHz load and it measured 49.87R on the VNA (with the same Ecal calibration) across about 2-10MHz. On the 4W Keithley this second Suhner load measured 49.89R at DC. So good agreement again I think.
Of course this doesn't necessarily mean that it will still be 50 ohms at 6GHz, which is I think what Dr Kirkby was saying.what i suspect he's saying is, albeit the inaccuracy of the load at DC and to some extend at RF, the error should be close to insignificant (for normal Joe's purposes).. but to know exactly, one has to make a comparison test requiring both the inaccurate load and super accurate $$$ load in hand, calibrate VNA with both and make few practical measurements to see how the measurements will be far off. i cant do the test since i cant justifiably afford $2,000 and beyond calibration kit let alone $13,000. so i have to anticipate more ripply measurement than it should. my 2cnts.
I think you also have to correct for the time delay in the SMA load I'm not sure how muddy things get if you were to try and do some precision work with a full 2 port VNA with an uncorrected 51.1R SMA load as the calibration reference. I wouldn't want to use it like that even if it would be OK for many casual tasks. I'm not sure I want to waste the time working out how much it will degrade certain types of measurement. I'd rather source a decent load and keep it simple :)
Can you make your measurements _more_ accurate by entering the exact resistance of the load?
Bud: Now the problem is to know your cal load RL, that you need to measure against a decent calibration kit on a VNA or from the manufacturer data.
In terms of a typical application for that old homebrew load I used it as part of my homebrew cal kit to design and verify a precision (SMA connector based) resistive splitter a few years ago. This was needed to help me service an ancient HP8405A vector voltmeter and verify the performance.
I used the cal kit to check out various SMD chip resistors (when piggybacked) to make up the resistors in the splitter. I wanted to match the performance of a decent commercial splitter up to the 1GHz range of the HP8405A. I needed ultra low port VSWR and sub 1degree phase balance and very good amplitude tracking on both arms of the splitter. To get this I needed resistances in each arm that were very close to 50.00R across LF to as close as 1GHz as possible. So I needed a decent cal kit for this.
I used my old/lowly HP8714B VNA and the homebrew cal kit to do all this because that is all I had back then. When I got the 4 port ENA VNA and the 4 port Ecal module I remeasured it formally as a 3 port device (to 3GHz!) and you can see the results below.
It was very impressive indeed for port VSWR, phase tracking and amplitude tracking across LF to 1GHz as you can see in the plots below. It degrades a bit by 3GHz but is still about as good as a typical commercial precision splitter up to 1GHz :)
That is impressive - I made a splitter as well but as I recall it is not even close to that performance.Thanks. A fair bit of design effort went into it and it would have been far more sensible to just buy a splitter ;D
I guess so but I don't know if a VNA would interpret this as a 51.1R resistor with a 50R Zo delay or as a 51.1R resistor with a 51.1R delay.I think if you leave the load connected after calibration and take a look at the smith chart you'll see how it interprets the 51.1R load. Anyway, in E5071? for instance? you can set offet Zo, impedance value and even offset loss. Although if you want to specify load impedance that is not 50R, then it will be a different standard - arbitary impedance. And I don't know if there are any limitations with using this kind of standards instead of usual loads.
Can't you enter the reference impedance value in the VNA settings and call it a day. Not all VNAs may have that setting changeable though.
Hi, is the suggested :Likely to be quite good enough for most measurements.
https://www.sdr-kits.net/index.php?route=product/product&path=66_68_69&product_id=50 (https://www.sdr-kits.net/index.php?route=product/product&path=66_68_69&product_id=50)
Kit useable for up to 3.2GHz im thinking abaout buying / hacking a SSA3021X-Plus but additional >>100€ for a calkit is said, the SSA is expensive enough for me..?
Is there a list which "official" calkits are supported from the cal menu?The Siglent Cal kits of course are all supported plus the crossover ones listed in this document:
Is there a list which "official" calkits are supported from the cal menu?
Sometimes i think tautech is an inoffical siglent fae crew account (multiple fae behind this account..) or maybe a very smart siglent bot / KI.. :-D so many posts in so many threads where do you work beside posting ? :-D
Is it worth to pay the "extra" for the SDR Kits Calkit (box, load measurment, male male Adapter) instead of buying the parts as "single" from Mouser?SOL are the minimum you need and some kits also come with a through but they are all rated to a max frequency and when swept to that frequency there must be little change across the full range.
Refering to:
http://www.hhft.de/index.php?page=competences&subpage=calibration (http://www.hhft.de/index.php?page=competences&subpage=calibration)
Mouser: 56€ + 16% vat inkl. shipping
SDR Kit : 75€ inkl. Vat + shipping (85€ total)
I think same parts and i think the only measured thing from SDR kits is resistive load resistor..
I can do this also with 4 wire measurment with my fluke8840a or?
Or are there more measurment done by them?
Male - male Adapter is sure also available from Mouser (didnt searched , not sure if i need this one...)
Suggestions??
Is it worth to pay the "extra" for the SDR Kits Calkit (box, load measurment, male male Adapter) instead of buying the parts as "single" from Mouser?well without providing CAL kit coefficients or s1p profiles, there is not such thing as even "Kirkby alternative", you can buy whatever cal kit you want and be happy about it, you can even make your own its doesnt matter. you can do the "inverse" or "reverse" profiling from whatever s1p/s2p plot from your VNA. if you care about Load quality that we all can measure with any DMM, you can get from already mentioned brand such as Rosenberger or whatever name they are you can browse the thread. or better, buy few Loads and hand pick which one is the closest to absolute "Fifty Ohms" and still cheaper compared to any knock off or "Kirkby alternative" buzzed/advertised as "CAL kit" out there (you can already have few terminations to test things such as 2/3/4/5 50 ohm signal splitter etc you are going to need it today or 10 years from now). you may get cheaper than your mentioned Mouser or SDR-kit's CAL kit at $50 and get a free (NanoVNA V2+ with decent quality 50ohm Zo SMA pigtail cables) if you buy from Tindie... or $4 this (https://www.aliexpress.com/item/4000976159786.html?spm=a2g0o.productlist.0.0.7700d560s3NF0O&algo_pvid=501af26c-e713-41d7-9a37-48c81d110c62&algo_expid=501af26c-e713-41d7-9a37-48c81d110c62-2&btsid=0bb0624516057699427837041ea718&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_)
Refering to:http://www.hhft.de/index.php?page=competences&subpage=calibration (http://www.hhft.de/index.php?page=competences&subpage=calibration)
Match / Load (female):this is what we call... Ideal Calibration Standard, even HP $20K CAL kit cant achieve this in reality. offset length can be measured physically with caliper, one eye closed and tongue at the right angle. electrical one way trip can be observed from VNA plot/TDR and punch the figure into the formula to get dielectric constant and hence "electrical length" aka "offset length". the deal here is to get 3rd degree polynomial approximation for those Cn and Ln up to whatever BW you are interested in, maybe those are negligible up to say 3-6GHz? i dont know. if someone can figure that out from "reverse" characterization from even a cheap VNA like NanoVNA alone, there is no reason to buy from Kirkby or HP at all, they should not be even mentioned in the first place, and there should not be any comparison to or no such thing as "Kirkby alternative" at all... $4 CAL kit is what we should look after if we dont care about polynomials, ymmv. cheers.
Offset Length: 0 mm
C-coefficients: all = 0 F / Hz
L-coefficients: all = 0 H / Hz
Short (female):
C-Coefficients: all = 0 F / Hz
L-Coefficients: all = 0 H / Hz
Open (female):
C-Coefficients: all = 0 F / Hz
L-Coefficients: all = 0 H / Hz
Thru (female / female):
Offset Length: 0 mm (The reference plane lies in the middle of the thru-connection)
There are more informations available:See what they're really like when you sweep them.
https://www.sdr-kits.net/documents/Rosenberger_Female_Cal_Standards_rev5.pdf (https://www.sdr-kits.net/documents/Rosenberger_Female_Cal_Standards_rev5.pdf)
So because they are "standard" Rosenberger types i think these informations are also true for the "single buy" mouser parts.
SDR-Kits are using the same parts like stated on the website. But I#m unsure if SDR-Kits are measuring anything "more" than the 50 Ohm impedance and write this value on top of the box...
If this is all there is no need to pay the "extra" if its only a small wood box...
This is what i mean. I think rosenberger parts are way more "true" even with this provided sheet against these cheap china parts (i already have delock 12GHz N->SMA Adapters, some decent SS405 2x (20cm) / 2x RG405 (1m) and some (10x 20cm / 2x 1m) RG316 cables for up to 3.2GHz (hopefully) also RG58 with bnc but these are <<1GHz useabel..) And all kind of "cheaper" SMA adaptors. Only a calkit with "stated true" things is missing (beside the china stuff) but 400$ if the whole VNA was only 1600€ is for hobby use a bit too much. So the rosenberger parts are (i think for hobby use) best bang/buck? And since i will not go higher than the 3.2GHz i think its sufficiant?
But I'm new to this stuff so i will need an advice.
compared to what? i can make a sloppy diy cal kit and make them flat to 6GHz on a VNA with zero offset everythings. one clue though to see a good LOAD without relative comparison is its return loss, but its real impedance and esp for OPEN and SHORT... you can be happy about anything.But I'm new to this stuff so i will need an advice.See what they're really like when you sweep them.
There are more informations available:i just noticed they use Thru as Open, to cut corner maybe? thats funny, as i read somewhere, the Open need to be shielded to reduce nasty/random "fringing capacitance" effect. you can download plenty of "Basics of VNA" and "Calibration Standard" materials esp good materials/appnotes from HP/Keysight and learn as you go, i'm also still learning, there are lots of things and maths to learn in this arena. :phew:
https://www.sdr-kits.net/documents/Rosenberger_Female_Cal_Standards_rev5.pdf (https://www.sdr-kits.net/documents/Rosenberger_Female_Cal_Standards_rev5.pdf)
So basically put a cheap china "open" on the other side of "thru" to close the shield?as i said it does not matter actually if we dont care about polynomials. but my thought is, if they want to sell a nice cal kit set, why they let us to go to trouble to buy separate shielded Open? maybe it will cost them only extra $1.
You cannot derive them from a mechanical measurement. You also cannot measure them on a VNA without calibrating it first against known standards.exactly my point in some of my earlier posts in the other threads too. but well, its not like the end of the world if we dont have a characterized CAL kit, it will not prohibit us from happy go learning. later i will look into how good a VNA can de-embed fixtures such as pcb, say if we want to probe at the very tip of smd components pad, i've been doing this for sometime by omitting cal parm and offsets, ie leave them all to 0, i will evaluate if my method is correct or what.
Never use male SMA connectors where you cannot rotate the barrel separately from the center pin (like in some cheap "calkits"). That is a sure way to eventually ruin the mating female connector.yes agreed. this one point that i didnt highlight but it can be a concern if you try to mate with expensive equipment or cable. so from this point of view, NanoVNA's short and the $4 kit i linked are bad. but since my KC901V is using cheap sacrificial N-sma, and NanoVNA is using equally cheap female sma connector, this is not really an issue imho, and i usually use cables that are male connectors, so they wont mate with those solid Short male directly, a thru will become sacrificial.
Buying a pack of cheap random loads on eBay and selecting those by DC resistance may end in disappointment. Some of those have really poor RF properties and even if you find one with 50.00Ohms at DC, it may be way off at a couple hundred MHz,agreed too as this is what i found out with a couple of Loads/terminators i bought from china (not meant for CAL kit). but to know this, you need a good CAL kit in the first place.
I don't know why all the cheap NanoVNAs all come with male ones.because the Nano has female input? or they figured it is better (more configurable) and they dont have to provide M-M thru. male cal kit can always be connected to F-F thru to get female version. i find F-F thru is inevitable and i very seldomly reach for M-M thru version.
I don't know why all the cheap NanoVNAs all come with male ones.because the Nano has female input? or they figured it is better (more configurable) and they dont have to provide M-M thru. male cal kit can always be connected to F-F thru to get female version. i find F-F thru is inevitable and i very seldomly reach for M-M thru version.
All the expensive calkits are already up to >>10GHz which is not needed for "cheap" VNAs like siglent ones which are only up to 3.2GHz. Why aren't there affordable ones for less than <150€ with measured values?Kirkby SMA kits thats advertised as 6GHz are specified to 12GHz using 20GHz calibrated HP VNA, dont ask the CAL kit he uses as The Reference. to convincingly rate a kit to 3GHz, you may want to specify to like what? 4-6GHz? using calibrated reputable brand VNA like HP/Agilent/Keysight, that is still expensive investment, dont ever call them to quote for the CAL kit alone we'll come back in shame, to get the idea, check on used (out of spec) market in ebay. if target customers are hobbiests, its sad hobbiest always aim for cheap price (me included), making this unpleasant business to venture. going to companies and universities, they will tend to go beyond 10GHz with todays 5G age. so you could end up with an expensive piece of paperweight on your desk without return profit. among all, most of Kirkby's customers are universities and professors thats impressed by him. we dont go into the know-how knowledge yet for the reliable calibration/verification process. inside the usb drive of CAL kit profiles, Kirkby included bunches of app notes relating to his work (i guess free non copyrighted) materials mostly from HP, i think i've only read one or two of the materials.
as i said it does not matter actually if we dont care about polynomials. but my thought is, if they want to sell a nice cal kit set, why they let us to go to trouble to buy separate shielded Open? maybe it will cost them only extra $1.Because it makes very little difference and if it does, it will likely make the performance slightly worse. Shielding an open standard does not help against fringing capacitance, it introduces more of it. If you think about it, the dust cap is essentially one plate of a capacitor. The same is true with these cheap male "calkits": don't bother with the open "standard", just leave the connector open. Use dustcaps to protect from dust, not for calibration.
Yes, the test port is (usually) female, but then most often there is a M-M test cable to connect to the DUT. And you really should calibrate at the end of the cable, not at the VNA port. "Converting" a cal kit with a F-F adapter will degrade performance significantly.I don't know why all the cheap NanoVNAs all come with male ones.because the Nano has female input? or they figured it is better (more configurable) and they dont have to provide M-M thru. male cal kit can always be connected to F-F thru to get female version. i find F-F thru is inevitable and i very seldomly reach for M-M thru version.
A decent / cheap "Calkit" for < 4-6 Ghz would be nice. All the expensive calkits are already up to >>10GHz which is not needed for "cheap" VNAs like siglent ones which are only up to 3.2GHz. Why aren't there affordable ones for less than <150€ with measured values?As you can see from the Rosenberger kit, the individual parts are not exactly free even without the characterization (if you want reliable parts from a reputable brand). And that is re-purposing jelly-bean parts like a thru for an open. Having a purpose-built open standard made in the really low volume we are talking about would be prohibitively expensive. And then you need an expensive VNA with a reference cal kit, pay for regular calibration and maintenance and pay for the lab technician who actually does the measurements.
"Converting" a cal kit with a F-F adapter will degrade performance significantly.imho no, except with extra effort to screw unscrew for connection and reduce usable life of the connectors. with good continuity/connectivity and good quality 50 ohm Zo thru, connecting to Open and Short will only increase its offset length, the rest of parameters are still the same. connecting to a good Load will still appear 50 ohm to the VNA. but well, this is true given the CAL set is of descent quality, if not, even a SMA cable or the sacrificial adapter connected to your VNA can look funny. this can quite visible beyond 3GHz and much lower with nonsense hunglow grade. ymmv.
For sure, i thought something like "calibrated" VNA with a "pogo plug SMA" and a machine putting it on the pogo plug, measure the value write it down into an excelsheet and throw away, put the next onto the pogo plugs.. something like that. "Fully automized" than calkits with SMA for <6GHz would be cheaper...
with a "pogo plug SMA"...oh no, dont! :palm:..
imho no, except with extra effort to screw unscrew for connection and reduce usable life of the connectors. with good continuity/connectivity and good quality 50 ohm Zo thru, connecting to Open and Short will only increase its offset length, the rest of parameters are still the same. connecting to a good Load will still appear 50 ohm to the VNA. but well, this is true given the CAL set is of descent quality, if not, even a SMA cable or the sacrificial adapter connected to your VNA can look funny. this can quite visible beyond 3GHz and much lower with nonsense hunglow grade. ymmv.
Item | Kirkby (https://www.kirkbymicrowave.co.uk/Sales-and-Services/Vector-network-analyzer-calibration-kits/SMA-calibration-kit/) £GBP | Kirkby (https://www.kirkbymicrowave.co.uk/Sales-and-Services/Vector-network-analyzer-calibration-kits/SMA-calibration-kit/) $USD | Applied EM (https://appliedeminnovations.com/product/calkit/) $USD |
6 GHz | 599 | ||
7 GHz | 485 | 578 | |
8 GHz | 513 | 648 | 649 |
Torque wrench | 150 | 189 | (included) |
I have the 10 GHz version of the Applied EM cal kit. I made some measurements on a FieldFox 9917B that was first calibrated with a Rosenberger RPC-3.50. The Fieldfox was set to full span (30 kHz - 18 GHz) with 1601 points. I then measured the female standards from the Applied EM kit and saved the s1p files. Also grabbed an s1p from the RPC-3.50.
I plotted the impedance, and it seems like the AEM kit does well up to ~10 GHz.
I quit after tearing my hair out for a good 2 hours trying to figure out the METAS tools, so if someone else can use it to generate a model I'd be grateful (and maybe post a link to a tutorial?)
I have the 10 GHz version of the Applied EM cal kit. I made some measurements on a FieldFox 9917B that was first calibrated with a Rosenberger RPC-3.50. The Fieldfox was set to full span (30 kHz - 18 GHz) with 1601 points. I then measured the female standards from the Applied EM kit and saved the s1p files. Also grabbed an s1p from the RPC-3.50.
I plotted the impedance, and it seems like the AEM kit does well up to ~10 GHz.
I quit after tearing my hair out for a good 2 hours trying to figure out the METAS tools, so if someone else can use it to generate a model I'd be grateful (and maybe post a link to a tutorial?)
Can you give the expected/specified Z0 offset and offset delay for the Applied EM kit. As was mentioned for it to work best you should know some of the parameters, or at least enter what they should ideally be to reduce the variables.
Short F | Offset Z0 (Ω) | Offset delay (ps) | Offset loss (GΩ⋅s-1) | L0 (10-12 H) | L1 (10-24 H⋅Hz-1) | L2 (10-33 H⋅Hz-2) | L3 (10-42 H⋅Hz-3) |
Given | 51.56 | 83.61 | 2.57 | -889.07 | 9989.25 | 9983.11 | -1413.8 |
Fitted | 51.524 | 81.139 | 6.2800 | -909.96 | 111076 | -14204 | 340.48 |
Open F | Offset Z0 (Ω) | Offset delay (ps) | Offset loss (GΩ⋅s-1) | C0 (10-15 F) | C1 (10-27 F⋅Hz-1) | C2 (10-36 F⋅Hz-2) | C3 (10-45 F⋅Hz-3) |
Given | 50 | 76.37 | 1.96 | -351.35 | -3947 | 1326.61 | -507.08 |
Fitted | 53.549 | 67.442 | 2.7871 | 46.597 | -90050 | 10138 | -358.16 |
Load F | Offset Z0 (Ω) | Offset delay (ps) | Offset loss (GΩ⋅s-1) | ||||
Given | 54.16 | 4.77 | 10 | ||||
Fitted | 54.253 | 8.4764 | -11.561 |
Short F | Offset Z0 (Ω) | Offset delay (ps) | Offset loss (GΩ⋅s-1) | L0 (10-12 H) | L1 (10-24 H⋅Hz-1) | L2 (10-33 H⋅Hz-2) | L3 (10-42 H⋅Hz-3) |
Given | 51.56 | 83.61 | 2.57 | -889.07 | 9989.25 | 9983.11 | -1413.8 |
Fitted | 52.319 | 85.325 | 1.0887 | -965.37 | -61723 | 29349 | -2997.3 |
Open F | Offset Z0 (Ω) | Offset delay (ps) | Offset loss (GΩ⋅s-1) | C0 (10-15 F) | C1 (10-27 F⋅Hz-1) | C2 (10-36 F⋅Hz-2) | C3 (10-45 F⋅Hz-3) |
Given | 50 | 76.37 | 1.96 | -351.35 | -3947 | 1326.61 | -507.08 |
Fitted | 52.277 | 77.447 | 1.2253 | -309.12 | -12284 | 219.52 | -456.68 |
Load F | Offset Z0 (Ω) | Offset delay (ps) | Offset loss (GΩ⋅s-1) | ||||
Given | 54.16 | 4.77 | 10 | ||||
Fitted 1* | 77.775 | 0.76737 | 340.06 | ||||
Fitted 2* | 54.142 | 6.2391 | 10.000 |