NanoVNA Custom Software

[joeqsmith]

Before anyone asks, the drift in the peak is real.  I don't have a calibrated beach towel over the jig and the air temperature will cause the crystal to to drift.

Wrong...

Changing the IFBW settings will change the peak's centroid.  Shown at 4kHz and 60kHz.

[jspencerg]

Re: winding torroids
What was the little white jacketed coax you used when making common mode chokes,  etc?  I've seen twisted pair used in other references. I assume the coaxial has better rf behavior, yes?

[joeqsmith]

Re: winding torroids
What was the little white jacketed coax you used when making common mode chokes,  etc?  I've seen twisted pair used in other references. I assume the coaxial has better rf behavior, yes?

Same coax from the last time you had asked.  Those transformers were characterized to 6GHz.  You can read about them in the manual or search this thread. 

https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg4063153/#msg4063153

[jspencerg]

Last time you referred to blue jacketed coax while the smaller stuff I saw was white. I'm thinking it was the rg188(from comparing spec's), but that does not seem right.  Because:  I have some rg316 with similar specified bend radius limit as the rg188. It seemed,  from watching video and comparing myself,  that the white coax you were wrapping was more flexible than rmin=.5".
So,  the rg188 is smallest you use?
Trivial stuff for you, but all new to me.
I am aquiring supplies to make transfer relay connections using rg400u
Thanks for the details.

[joeqsmith]

Common sizes I use. 

[joeqsmith]

900MHz center, 100kHz span, 2 sweeps per setting,  sweeping IFBF from 400Hz to 60kHz. 

[joeqsmith]

Same setup but at 5MHz. 

[jspencerg]

Could you replace sweeps with center frequency?  Run from 5M to 900M. Still show delta f.

[joeqsmith]

Could you replace sweeps with center frequency?  Run from 5M to 900M. Still show delta f.

I think I understand.  You want to sweep the frequency with some fixed span and fixed frequency step size.  If so, yes I can do this.   However,  think about what you are suggesting.  You have not fully considered what you are asking or I am not understanding.   There's some missing details, or at least one major one...   

[jspencerg]

Just brainstorming: How would peak and lobe profile change as frequency changed?

[joeqsmith]

Re: brainstorming: How would peak and lobe profile change as frequency changed?

Well, our ideas of brainstorming differ.  Think about it.  What causes the peaks and lobes?

[jspencerg]

Haha. Our capacities to constructively brainstorm differ by several orders of magnitude because of difference in referential knowledge.  Fancy way of referring to my ignorance.
I realized, after some thought, that even if one had a dut with adjustable frequency response, the resonance (or whatever) would likely not be the same at each frequency.  So,  that probably would not be a good experiment to investigate the measuring behavior of the VNA.
I discovered why your rg188 seemed so flexible.  The ptfe jacket makes it so.  That is some fancy wire.  I found some mil spec new old stock from 1981 for a good price.
Figuring out wire routing for the transfer relay.  Your images help.

[joeqsmith]

Re: brainstorming

Bingo.  I already sweep the frequency with the span and I also sweep the IFBW.  Nothing there changes except we widen the span.  But to look at narrow band signals... 

We could look at the effects of IFBW on a wideband signal over some very wide freq sweep (basically look at the noise floor) but I don't think we would see anything of interest.   If I were for example to run the previous IFBW sweep using that interdigital GHz filter for example, the lobes are going to stay the same but the noise floor will change.   Even looking at the crystal filters I made is fine.  It's really just when looking at the crystals themselves or a very narrow source.

Your talking to the king of ignorance.   Mine knows no bounds and expands each day.   lol. 

If you are interested in working at these higher frequencies, cable choice is important.  RG174 while very flexible by comparison would make a poor choice.   Pasternak has most of these cables in stock and will sell it in shorter sections.  Digi-key may also carry something you could use. 

The jacket on my blue cables that I showed in many videos with the NanoVNA cracked after a few years of use.   Just too much flexing when running so many demos.

[jspencerg]

Re: cable choices.
I chose the rg400 for transfer relay connections as effort to make best setup knowing I will have minimal flex and  want great quality connection(best I can).
I'm wanting to investigate inductors, chose this high-end rg188 to minimize Impedence changes in wire with frequency.  The rg178 I have is stiff. I'll respect bend radius.
Re: Transfer relay
I read proof for using t-check to examine quality of two-port measurement(using transfer relay in my case).  More reading seems to say that most circuits are expected to be reciprocal for s12 and s21, which seems to relegate use of full 2-port measurements to checking when dut is well- behaved.  Two questions:
1. Are there any non-reciprocal dut's I could study?
2. Do you use full two-port measurements to judge quality of a dut that is supposed to be reciprocal w.re.to s12 and s21?

[joeqsmith]

Re: questions
I had wondered why you were attempting to integrate a transfer relay.

1. Are there any non-reciprocal dut's I could study?

Yes, there are non-reciprocal DUTs.  Mixers, directional couplers, matching transformers to name a few.   You could study them from a text book and then attempt to gain a deeper understanding by experimenting with them.   You could even build your own devices.   Experimenting with a 4:1 transformer would be simple enough.   You would certainly see a difference.

2. Do you use full two-port measurements to judge quality of a dut that is supposed to be reciprocal w.re.to s12 and s21?

No.  I do use the reciprocal to judge the quality of my calibration. 

I'm wanting to investigate inductors

 
I made a video where I used the original NanoVNA to make several measurements including Ls, Cs & Rs all without a transfer relay.

Make sure you have a reason to use the transfer relay.  Adding one will only add to the error and may create problems. 

[jspencerg]

Thanks for suggestions. Perhaps I would not have undertaken the relay project if I'd realized limited applications.  I'm invested in getting it together and seeing how well I can do with it.

I've watched a lot of demonstrated activities using inductors. Inductors seem more interesting and varied than behaviors of capacitors. Lots of variables.

Yes, I'm trying to figure out, build and always use setups which will minimize errors.  This is a challenge I like to work on using my limited but growing electronics bench.

[joeqsmith]

Re: realized limited applications

You may find your time is better spent reading than buying parts.  Trying to build something with little understanding of what you are doing or why makes little sense to me.   Then again, I rolled two custom xfer relays with zero success along with wrote some software to support them just for the fun of it. 

Most of the videos I have watched on VNAs were from CMT, Picotest, RS.  These are normally more generic.   The last one I watched prompted me to make that rebuttal video.  Recently this person commented  how their V2Plus4 uses sine wave.   It was only the bad clones using square waves.   I suggested they post here and show us some data but they pulled their comment. 

Most of the test loads I had looked at were standard purchased parts.  They come with data sheets.   I advice you to start out measuring parts that you know what their specs are before diving into the unknown.  For variables, I think it just depends how deep you want to dive in.   We had a little contest some time ago about constructing an oscillator on a breadboard for the fun of it.  I asked about when the person who started the thread considered a jumper wire an inductor, capacitor, delay line.   Some of the demos I made for the V2Plus4 were nothing more than some blank FR4 material and copper foil. 

[jspencerg]

Yes,  aquiring unnecessary stuff if a waste. I found a 30-year old oscilloscope that is way more than I need,  but it's capabilities are there when I learn and think of new ways to use it.
I thought your oscillator solution reflected your experience gained from wire wrapping work.  I'd think those constructions were often bumping against frequency limits (complications)  due to resonances,  etc.
Of course,  pursuing the simple questions can lead to elegant insights.  I'm not looking beyond getting some personal learning. 
Looking forward to your sharing more of your experiments.

[realfran]

Hello, for the transfer relay this datasheet help to choose the configuration of it. Agilent-33311B-Datasheet.pdf (806.18 kB - downloaded 188 times.)

[jspencerg]

Re: Transfer relay
Thank you but I aquired a new/old transco relay on ebay. I've almost received all ordered parts necessary to put it together. I've got a plan. Time to see if it works!

[jspencerg]

Joe,  I truely appreciate the programs you've created and shared.   I wish there were a way to entice you to document the features.  I'm making efforts to puzzle choices out as I (try) testing new setups. However,  measurement returns aren't perfect(nature of rf, connections etc) which really hinders being able to decide whether I'm on the right track.  This wandering in the dark likely means I'll never recognize some really important features.

[jspencerg]

This would be a cool experiment.  Could this be done with the nanovna's?
https://coppermountaintech.com/determining-resonator-q-factor-from-return-loss-measurement-alone/

[joeqsmith]

Re: cool experiment

Again, I am not sure what you are asking.  Obviously these low cost VNAs can measure S11 & S21.   So I read the paper thinking maybe there was something there that would make you ask.  It seemed straightforward enough.    Lets spend a few minutes and toss something together.

I don't have a 1uH, so wound up a coil on a chapstick dispenser.  For the 113pF, I used a 100pF // with a trimmer.  For the 2k, I used a 2k21. For the 12pF coupling caps, I used 22pF.   

I have a James Millen Grid-Dip meter model 90651, serial number 16.  Released in 1949.  Shown with the 6.4-16MHz orange coil.  The trimmer was set to provide a dip at 14MHz.

Tank was then attached to the Lite.  No calibration was performed.   Measuring Q with S11,  13.290M / 980k = 13.56. 

Obviously, a swag at best but I see no reason why anyone couldn't follow this paper and replicate the test with the low cost VNAs.

***
Just to give some idea on the error,  assuming the RLC meter and resonance frequency of the Lite are close (which they are)  1.055uH @ 13.29MHz gives an XL of 88.1.  From this we can calculate C at 136pF.  With the 2k2, we should have a Q of 25.  We came up with about half that....  Lots of error compared with the paper, but again no calibration and our coupling network is a bit off...   

[jspencerg]

Dang, you're fast.  Thanks for pic's. Being able to replicate, do calculations and compare results will be good learning experience for me.  Will study provided details later.
I was just reading about sample averaging. Recall you stated you used running average of last 100(?) samples.  That is a linear weighting scheme?  Did you consider using an exponential weighting scheme?  Using LV  seems a real advantage in implementing signal processing.
Could you also explain the 'smooth' function you have?
Thanks.

[joeqsmith]

Ok, so no questions about the cool experiment.  I figured you had a reason to ask but guess not. 

Smooth uses an FIR.  The old software for the original NanoVNA does not support the average feature.  The following shows how to calculate an average: