NanoVNA Custom Software

[joeqsmith]

ALW, check what my software is reporting for sweep time with your setup.  Is it a stable 250ms or does it jump around to 500, 750 ms? 

[ALW]

As you said, the SW is a bit bitchy in CW mode. It looks like, if I click on pnts first, CWfrequ 2nd, sweep time is around 250 ms. If I click the other way round (last click on pnts), the reference subtraction in the polar plot is not working anymore and the sweep time is indicated at around 450.
However, I figured that out early on that you need to do a click on CW frequ as last action in order to have CW working. I use your ref-sub feature for all my radar tests, and it messes completely up if you do not follow that rule.
When going to your raw data tab, it looks that clicking on "points" activates a frequ sweep mode, abandoning the CW mode previously selected.
(That is one of the reasons why I suggested earlier to indicate somehow if we are in "center span" "min/max" or "CW" mode)
Interestingly, the S21 data recorded seem to come with 5 ms interval. This may mean, that the 2.5 ms is for S11 and S21 combined

[joeqsmith]

The order is by design.  The manual warns about the importance of ordering but I don't think I go into the details for CW.

Selecting the points will program the VNA with whatever the current start and stop frequencies are.   Selecting CW will override the step size, forcing it to zero.   If you select anything other than CW last, that step size will be overwritten.   

Assuming that you enter CW correctly and you are seeing around 250ms, how much does it jump around if you watch it for 30 seconds or so?  +/-50ms or +250ms or more? 

[ALW]

251-265 ms
However, immediately(1st 10 s) after switching to the task it is more span. Seems to relate to cpu load somehow
I played with the num of points a bit and it is reasonably always a factor of 2.5 give or take 5%. When you activate the raw data tab that slows it down a bit.

[joeqsmith]

That's much better than I was expecting compared with my PC.   There is a newer version that I had corrected the units case (K vs k)  and I will go ahead and addresses this problem with CW to make it a bit more robust.

Attached, I have further aggravated the problem prior to adding the change.    With these being very minor changes and yours being stable, I won't worry about releasing it. 

(That is one of the reasons why I suggested earlier to indicate somehow if we are in "center span" "min/max" or "CW" mode)
Interestingly, the S21 data recorded seem to come with 5 ms interval. This may mean, that the 2.5 ms is for S11 and S21 combined

It will always be in the last mode selected, unless you change the number of points.  As I mentioned, there is also the segmented sweep to consider.   A simple way would be to change the fonts colors to reflect the mode currently selected.   Basically as shown. 

IMPORTANT!!!!
There is an order to selecting the data.  The software will always program the V2+ to the last setting you made.  If you change Fcenter, the software will use the center and span to calculate the new range.  If you change Fmin, the software will use the min (start) and max (stop) to calculate the range.   If you were to program the min and max first, then change the span, the V2+’s start and stop would change. 
Also, changing the number of points will cause the software to recalculate the sweep range based on the min (start) and max (stop). 

[joeqsmith]

Let me know if you want to try it.

[joeqsmith]

Interestingly, the S21 data recorded seem to come with 5 ms interval. This may mean, that the 2.5 ms is for S11 and S21 combined

The V2Plus sends everything for each data point.  It's not like the original NanoVNA in that regard where you can pick a choose what you want.   

The software does not discretely write every sample it receives.  Rather it places the entire swept data set into a queue.  Once an  entire error free data set has been received, the software then writes it to the file and plots it to the screen.   So for 101 data points, I am expecting the software to write out 101 data points for both channels every 250ms. 

***
Setting the software for 2.4GHz CW, 101 data points and recording for 1 minute, should provide 60 * 4 *101 = 24,240 points.

Letting it record and timing it by hand, using that converter I provided and importing to Excel, it seems to work out. 

[ALW]

Let me know if you want to try it.

Sure I want to try it! I like the coloring of the font.

As for my application, I will try to record a pendulum movement with video and with the nano radar for getting the time base tested.

[joeqsmith]

Let me know if you want to try it.

Sure I want to try it! I like the coloring of the font.

As for my application, I will try to record a pendulum movement with video and with the nano radar for getting the time base tested.

2.04 is on-line.  Minimal testing but the changes were fairly minor.   

[joeqsmith]

Rather than a pendulum,  I am just moving the connectors.  I start out fairly slow then increased my speed.   You may need a fairly fast camera and a few hundred hz pendulum. 

Depending what you have on-hand for equipment, maybe just use an ARB in burst mode.  Or just connect the two ports with a switch and pulse it.   I think those GaAs parts I used would switch well below 10ns.   Certainly fast enough for this experiment.

I have that first gen transfer relay that would work fine for this.  I could easily collect the data for you if you knew how you wanted to run it. 

[joeqsmith]

I placed the GaAs xfer relay between the two ports and controlled it from the Arb.  Starting at 100mHz and stepping 100mHz to 1Hz.  Then incrementing by 1Hz to 10Hz.  Then incrementing by 10Hz, and so on.   Using 500MHz 101 data points to stay well within the range of the switches.   

Its a simple test so if you find the data useful, I can run it how ever you want.   

[joeqsmith]

Switching at a fixed 100Hz 50% DC.   

[joeqsmith]

Switching at 500Hz. 

***
Should add that I had changed to 401 data points to collect this data. 

[ALW]

Didn't look at the rest yet, it's late here. But your 100Hz data look like 2 points up, 2 points down. That means we are sampling at 200 Hz / 5 ms interval, correct? Will call it a day now, thanks a lot for the help.

[joeqsmith]

The Signal Hound was measuring a sample rate of around 500us (2kHz).   At 1kHz we can see it starting to alias as we would expect. 

It does all appear to make sense.

[joeqsmith]

Didn't look at the rest yet, it's late here. But your 100Hz data look like 2 points up, 2 points down. That means we are sampling at 200 Hz / 5 ms interval, correct? Will call it a day now, thanks a lot for the help.

Notice on the 500Hz dataset, we have 2 points up, 2 points down or 4 X 500Hz or 2KHz, or 500us which is what we had measured with the Signal Hound.   


****
From the manual, we know they at least mention you can get 400 points per second out of it.  It needs to at least be able to sample at 400sps to achieve that. 

https://nanorfe.com/nanovna-v2-user-manual.html

[ALW]

your stepped switch interval was very helpful. I marked the switch event row number and did the math (see attached table). The sampling rate of the NanoV2+4 FW is 200 Hz, which I was also told in https://groups.io/g/NanoVNAV2/messages?expanded=1&msgnum=2336

Your 100 Hz switch shows 2 points up, 2 down, also in agreement with a 200 Hz sampling rate. With the 500 Hz switching you are switching faster than recording, showing some harmonic of the two rates I guess.

The tx behavior you see with the spectrum analyzer is a different chapter IMHO.

Thanks!

[ALW]

Sample rate 200 Hz puts my radar heartbeat recording into a healthy corner,  at about 120 beats per min showing my excitement about the radar working (I started getting worried, if it was a 500 Hz sample rate I may have needed intensive care )

[joeqsmith]

your stepped switch interval was very helpful. I marked the switch event row number and did the math (see attached table). The sampling rate of the NanoV2+4 FW is 200 Hz, which I was also told in https://groups.io/g/NanoVNAV2/messages?expanded=1&msgnum=2336

Your 100 Hz switch shows 2 points up, 2 down, also in agreement with a 200 Hz sampling rate. With the 500 Hz switching you are switching faster than recording, showing some harmonic of the two rates I guess.

The tx behavior you see with the spectrum analyzer is a different chapter IMHO.

Thanks!

It's certainly possible it's aliasing the crap out of it at 500.     

100Hz is a period of 0.010 seconds.  2 points per level or 4 points per period.   10ms / 4 is 2.5ms per sample, or 400Hz (1 / 2.5ms).  Not 200. 

Also, the 400 samples per second called out in the manual makes no sense with a 200Hz sample rate. 

When you ask a question on the internet, be careful about what you are asking and who you are asking.  Like an under sampled system, it's very easy to be led astray.

***
Knowing its 4 points per period, you know its 4 X 100Hz, or 400Hz. 

[joeqsmith]

Let me know what you think about that color selection.  Try all the various modes.  If you think it would be helpful, I may add it to the software for the original.

[ALW]

In your stepped switching expt you switched at 100 mHz meaning your switching interval (event to event, no matter if up or down) was 10 s initially, then 5 s, then 3 1/3 s and so on, correct?

Yes, I love your font color indicator. Now I would have known right away what mode I am in right now, would have steepened my learning curve of your SW massively :-) . Another thought I had: one could simply change all the numbers according to the last defining input. E.g. CWmode: fmax=fmin=fcenter, span = 0. Max/Min mode: Fcenter=(fmax+fmin)/2, span = fmax-fmin etc.

[joeqsmith]

In your stepped switching expt you switched at 100 mHz meaning your switching interval (event to event, no matter if up or down) was 10 s initially, then 5 s, then 3 1/3 s and so on, correct?

I think so but don't quote me on it.  Was more just to give you some idea what could be done if you wanted to try and collect some data this way.  There may not even be enough data to make heads or tails out of it.   I didn't get any feedback from you, so I forged ahead with the fixed rates. 

[joeqsmith]

Yes, I love your font color indicator. Now I would have known right away what mode I am in right now, would have steepened my learning curve of your SW massively :-) . Another thought I had: one could simply change all the numbers according to the last defining input. E.g. CWmode: fMax=fmin, span = 0.

Not a fan of having the software overwrite the controls.  Random button pushers will end up having to reenter their settings often.

[ALW]

Getting your point, but I guess we are coming from different worlds in this regard. In the medical device industry we are trying to make a user interface as intuitive and foolproof as possible. We need to take the buttonpushers (and worse) along. The insulin pump must be also usable by grandma... Big companies have entire usability departments dedicated to this.

Here, I believe it is just 3 different ways to enter the same parameters in the end. Those parameters are interdependent, and it would be more logic and intuitive if the entries would reflect those dependencies IMHO.

But, having said that, grandma will probably not use the VNA...

[joeqsmith]

Getting your point, but I guess we are coming from different worlds in this regard. In the medical device industry we are trying to make a user interface as intuitive and foolproof as possible. We need to take the buttonpushers (and worse) along. The insulin pump must be also usable by grandma... Big companies have entire usability departments dedicated to this.

Here, I believe it is just 3 different ways to enter the same parameters in the end. Those parameters are interdependent, and it would be more logic and intuitive if the entries would reflect those dependencies IMHO.

But, having said that, grandma will probably not use the VNA...

For my software, there is no big company or usability department.  It's a home project intended to be used by engineers (EEs) starting out in RF.  Of course, there are the radio hobbyists who write me about their troubles trying to read their SWR before they enter their next contest (advancing the art).  They are an aging group and I am sure include some grandmas as well.     

In my case, there is no "need" to support anyone as there are no customers.   There's no business, no profits and a fair amount of lost time.   It's a hobby.    Comparing it to any business in any sector makes no sense.   

If you read the manual for the V2Plus4, to set the sweep range you  have a Start and Step frequency.  That's it.  Yes, CW, start/stop, center/span all get converted into these two numbers.   Yes, the UI could just present these two numbers and be done with it.   The software also supports a handful of VNAs.   Each is unique in how they are controlled but I could convert them to use the start and step.   To be clear, I could but won't. 

UIs are a very subjective topic.  MBAs love this stuff because it's not requiring any technical skills.  Everyone will have an opinion about how it should work, look, scale.....   Personally, I see it as a black hole and for a home project, it's not my area of interest.   One more reason I use LabView.... 

That said, I have not bought test equipment because the company appeared to hire all new staff with new managers and failed to look at all of their previous products and how they worked.  The new groups are made up of only the best people and have great new ideas.  They want to show the right way to do it because the old way is just old.    So, I fully agree when it comes to a real company, they better have there act together.