开云体育

Another suggestion to reduce novice frustration is to advise them to download the ST files using a PC that has their email client installed, in order to pass ST’s identity verification scheme.

Regards,
Bruce W4CG

Thanks for the link; that is a useful resource. - Ed

On Sat, Jan 25, 2020 at 09:19 AM, Jos Stevens wrote:

" I'm testing my new NanoVna-H4 iusing NanoVNA-Saver and have a problem doing the 2 port calibration"
=======================================================================================

Jos,
I just performed a full 2-port calibration of my NanoVNA-H4 using NanoVNA-Saver and did not experience any problems. Did you use the calibration wizard? It should direct you through a full 1-port calibration and then ask if you want to continue with a 2-port calibration. If you follow the directions and still have problems with s21 results, then you may want to verify that the cables and barrel you are using for through calibration are not defective (it occasionally happens).

- Herb

Here are polar plots for CH1 connected to CH0
corrected vs uncorrected

Are there others that have seen this ?

Here are screen captures from my "worse clone"
for uncorrected vs corrected

I'm testing my new NanoVna-H4 iusing NanoVNA-Saver and have? a problem doing the 2 port calibration .

When I have done the last item of the calibration procedure (through) I see a nice sinewave-like trace around zero in the S21 Chart. This obviously is the uncalbrated S21.

When I press "apply"? this trace should be? updated? closer to 0 by the correction, but instead of that it drops down 35dB with a lot of noise above 900 MHz . The other charts are updated correctly as far as I can see.

The same thing happens ofcourse when the calibration has been saved and (re)used.

Are there others that have seen this ?

Jos

Interesting, the link goes to a channel that says there are no videos!

3 part video tutorial

Link added in /g/nanovna-users/wiki/User-Guides

I just reconfirmed it working using a different (Safari) browser not logged into YouTube

Does anyone else see the same symptom?

No, but I do not have semi rigid coax..

First measurement using 35cm RG316 shows loss from 250-400MHz.
Second measurement using longer LMR-400 shows loss from 41.67-66.67MHz,
approximately matching the frequency/length ratio.

I did not bother recalibrating, since I would expect that to only impact accuracy, not relative frequency-dependent losses..

Interesting, the link goes to a channel that says there are no videos!

Roy
WA0YMH

On Fri, Jan 24, 2020 at 09:26 AM, Norbert Kohns wrote:

I am wondering, that at full reflection the response moves over the perimeter
of the smith chart.

Hello Norbert,
I think it has to do with calibration.

After calibration direct at the nanoVNA CH0 SMA female plug, a 1 m coax cable connected to the reference plane with open at its other end, should give *perfect circles spiraling inwards* in the smith chart, see below.

In the program nanoVNA-saver *no extra calibration* was used.

Compared with the measured 101 points of the nanoVNA, the curve in the nanoVNA-saver program looks much smoother with 505 points. See the picture on the right and below.

For more details have a look to my web page:


73, Rudi DL5FA

There exist a very good kindle e.book about the Nano Vna :



73 de Klaus, DL7AIR

On Sat, Jan 25, 2020 at 04:54 AM, <sidebores@...> wrote:

Can someone tell me please do you have to calibrate everytime you change the start and stop frequency limits. Or is the cal good if its within the original cal eg 50Mhz to 400Mhz to 70Mhz to 300Mhz.
==================================================================

The best way to judge for yourself whether re-calibrating is necessary is to do the math.

The NanoVNA only has 101 measurement points available so if your original calibration range was 50 kHz - 900 MHz, then your calibration points are spaced every (900e6-50e3)/101 = ~8.9 MHz. If you were to change the measurement range to 50 kHz - 30 MHz then there are only 3 calibration points within that range. and almost all of your measurement data will be interpolated from those three measurement points. If your device under test (DUT) has a broad response then you may not notice any error. If the DUT has a lot of narrowband responses then the error can be significant.

In the test case you presented where the original calibration was 50Mhz - 400Mhz, then the calibration points are spaced every (400e6-50-6)/101 = ~3.5 MHz. If you change the range to 70Mhz - 300Mhz, then you have about 67 calibration points in that range which may be sufficient enough to not warrant re-calibration.

If you find yourself using the same measurement ranges on a regular basis, then calibrate and save those ranges to any of the other 4 memory locations and then you can recall them without re-doing the calibration at any time.

- Herb

A source of useful VNA application information at -

linked in /g/nanovna-users/wiki/Application-Notes#Collected-wisdom

A source of useful VNA application information at -

Hello Kev,

Interpolation is used, however the routine is not so robust that it would precisely apply without some error introduced. Hence, if I recall you will see
a cal* symbol display. If you desire the best accuracy and do not desire a re cal, best to pre cal and store sweep ranges that best meet your measurement needs. Some of the big box vna devices force you to turn interpolation on prior to changing the sweep range after a cal. Otherwise they drop out of cal after a sweep range is set and cal completed and sweep range changed!

You can limit yourself to the previous calibration.
But this is not entirely correct if you want to take measurements on a narrower part of the range.
It is advisable to have a calibration for this range.

Hello there,
Can someone tell me please do you have to calibrate everytime you change the start and stop frequency limits. Or is the cal good if its within the original cal eg 50Mhz to 400Mhz to 70Mhz to 300Mhz.

Cheers Kev

On Sat, Jan 25, 2020 at 02:06 AM, Gyula Molnar wrote:

" is this problem even without USB connection?
Does it return a negative number even when there is no connection between your computer and nano? "
==============================================================
Hi Gyula,
The NanoVNA-H4 has been working well, except for the center frequency above 1 GHz glitch. The lock-up occurs regardless of whether the NanoVNA-H4 is connected to a computer or not. The work around for now is to set the frequency limits using start and stop, rather than center frequency and span.

Ken Liao's release was developed on a Linux machine and there are some Windows related issues that he didn't foresee.

No hardware issues have been observed so far. The above firmware related issues are fixable. The 4" display is a welcome improvement over the 2.8" NanoVNA. I have noticed there are still some occasional display refresh artifacts, as on the NanoVNA-H, and may be something we just have to come to live with.

Hope your unit arrives soon.

- Herb

Hi Gabriel
It still looks pretty fine. A S11 dB with e.g. 0.1dB/division will tell you a lot compared to a simulated line in SmithChart.
A shorted line does not have the S11 sloping trace the first few 100 MHz as well, due to where the stub is acting as a "real" transmission line .
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af Gabriel Tenma White
Sendt: 25. januar 2020 05:10
Til: [email protected]
Emne: Re: [nanovna-users] First PCB pictures of the V2

Ok it looks like I need to do more work on the cal kit parameters. Previously the software only took S parameter files for cal kit definitions, and I've only added a "fine tune" UI which does length extension the configured S parameters (and adds parasitics for the load standard).

The hardware hasn't changed since the December revision (V2_2), which is the revision they are using for production. The next hardware revision will be an experimental one, with changes like an amplifier on channel 0 and port 2 ecal features.

Here is one sample from production:
Note that the enclosure is still not finalized and for the first few weeks the VNA will be sold without an enclosure at reduced price I've heard. There are still some fit issues related to the connectors that need to be fixed and enclosure manufacturing will take some time as well.

One BNC-binding post adapter should be flipped
to allow thru calibration without crossed wires