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One Month Assessment


hwalker 2020/04/29 09:33

I received my NanoVNA-V2 (S-A-A-2) a month ago, about the same time as most other owners who ordered from the first production run. The first run sold out within a couple of weeks, as did the second production run when it was offered on Tindie by hcxqsgroup. Both production runs were sold for $58.00 usd. Currently, the only available units I see on eBay are being sold by third party resellers for almost 3 times the Tindie price. hcxqsgroup could easily have raised the price on the second production run due to demand, but did not do so. There were also a limited number of NanoVNA-V2's with accessory kit (SOLT standards + RG405 cables) sold for an additional $10.00 USD, which had to be close to cost and was a great value.

Shipping delays caused by the COVID-19 crisis have resulted in complaints and less than stellar reviews of the NanoVNA-V2 by some buyers. Gabriel posted that the poor reviews have caused hcxqsgroup to consider delaying a third production run until a more reliable shipping option can be worked out. From similar shipping delay reports on other NanoVNA-H and NanoVNA-F forums, I not sure if a more reliable shipping option is currently available.

Actual user reports over the course of the last month have shown that Gabriel and her OwOComm hardware, firmware and software design team did a top notch job in bringing the NanoVNA-V2 to the market. For a version one product it has had remarkably few issues reported by users. The following is a summary of the feedback received by users in the areas of software, firmware and hardware over the last month.

Software:
1. Currently NanoVNA/QT and TAPR ver 4.6 are the only released applications that work with NanoVNA-V2. NanoVNA/QT is available at https://github.com/nanovna/NanoVNA-QT/releases and TAPR ver 4.6 is available at https://groups.io/g/nanovna-users/files/NanoVNA%20PC%20Software/TAPR%20VNA/VNAR4.6.zip .

2. A beta branch version of NanoVNA-Saver by Holger Müller is available at https://github.com/zarath/nanovna-saver/tree/feature/nanovna-v2 . It worked fine on my Windows 10 system except I could never get the through calibration standard to zero properly. If you beta test this version and find any issues be sure to pass them on to Holger so he can in turn integrate any fixes into his merge request to the next release version of Rune's NanoVNA-Saver.

3. NanoVNA/QT is a perfectly usable application, although NanoVNA-Saver users will miss its more flexible scaling and charting options. The only NanoVNA/QT issue that has been reported under both Windows and Linux is that a saved .cal file could not be reloaded. It turned out to be a locality issue that Gabriel will address in the next software release.

Per Gabriel, "Found the bug; it's because of incorrect number formatting when saving .cal files depending on the locale. I'll get the fix into the next release. For now if you open the .cal files in a text editor and find/replace all instances of , (comma) with . (period) it will load correctly."

4. Kurt Poulsen posted, "... S21/S12 measurements are a bit off by insertion loss (not a serious problem) and for delay by the thru adapter delay and the phase sync between S11 and S21 are lost. Gabriel have promised to look into the code."

5. Rens Dijkshoorn posted, "just found that the current Github has added support for MacPort and Homebrew for installing the NanoVNA-QT app. .... I found that you have to define the USB device using Other under Devicec tab to /dev/cu.usbmodemDEM1 whichis the same what is already set. De nanoVNA-2 display should then o black and display NanoVNA V2_2 USB MODE. Tested on OSX 10.11.6

Firmware:
1. Firmware upgrades can currently only be done from NanoVNA/QT or a python script on Linux. Per Gabriel, "Latest NanoVNA-QT on windows should be able to do the firmware update, but I recommend having a linux machine ready in case the update goes wrong."

2. The NanoVNA-V2 has a port, CON303, available for using an ST-link for flashing (firmware upgrade).

3. Turning off all display traces or displaying only trace 2 by itself corrupts the display. Per Gabriel, "I can confirm the issue. It looks like at least one trace (other than smith chart) has to be selected or else it triggers the bug. I'll get it fixed by next release."

4. The firmware supports either a 2.8" or 3.2" SPI TFT Display Module. The same character set is used for either module so visual acuity is about the same.

5. The NanoVNA-V2 goes into "USB Mode" whenever a command is sent to it and requires power cycling to exit "USB Mode". That is an in-eloquent way of communicating with the NanoVNA-V2. hcxsgroup has responded, "The exiting USB mode problem is being worked on and should be fixed by next firmware release in a week or so." And per Gabriel, " USB mode exit should be a trivial fix; they are working on that I think. Right now my biggest task on the firmware is adding moonrunes support which a lot of their domestic users are asking for."

6. The latest firmware releases can be found at: https://github.com/nanovna/NanoVNA-V2-firmware/releases

Hardware:
1. The most requested hardware feature for the NanoVNA-V2 has been a 4-in display. Gabriel plans on supporting the ST7796S 4" display and said there is "good command set compatibility between the ST7796S and ILI9341". Support for the 4" display has to take a back seat to adding moonrunes support. The only way It might happen sooner is if hugen decides to second source a 4" NanoVNA-V2 and writes the display driver himself.

2. Above 140 MHz the minimum NanoVNA-V2 frequency step is 12 kHz. Per Gabriel, "I think the minimum doable step size is 6kHz, limited by the maximum modulus of the adf4350 fractional synthesizer which is 4096. The reference clock is 24MHz, and 24MHz / 4000 = 6kHz. I see that it's set to 12kHz step size in the code; I'll try 6kHz tomorrow and see if there are any problems."

3. The S-A-A-2 defaults to an un-calibrated state at power-up. It does not automatically re-store "C0" at power-up as the as the NanoVNA does. You have to manually recall C0 to restore your calibration. One user commented, "I think this was a good decision. It does not force you to do a new calibration, but it does remind you, that you are going to use an old calibration. HP/Agilent/... analyzers all work this way."

4. There is a "Flip Display" button in the "Display" menu. The flip status is saved with the "Save" button in the "Config" menu.

5. The USB interface always outputs raw, uncalibrated values, as is in the user manual. Per Gabriel, "The reason is the assumption that the PC software always has superior calibration routines (e.g. supporting arbitrary cal kit parameters) and it is far less error prone if you can't be confused whether you are reading calibrated or uncalibrated values."

6. The VNA logic in the firmware was written from scratch, and calibration interpolation wasn't implemented. This means if you change frequencies no interpolation is performed and you return to an uncalibrated state. Per Gabriel, "Personally I've not had good experience with using interpolation on other VNAs that support it; I've found it to give wrong results every time unless you have an insanely high number of sweep points (1000). However if there is popular demand we can go and implement interpolation (as done on the NanoVNA -herb)."

7. The ECAL feature of the NanoVNA-V2 has been confused with a "self calibration" feature. Per Gabriel, "There is no "self cal". There are corrections to track temperature drift, but this is not a full SOL calibration. The corrections are always happening and every sweep some small percentage of the time is allocated to it, except for the first sweep after changing frequency range which performs a full correction sweep, which is why the first sweep is much slower. If you compare the V2 to V1 you should see a big difference in temperature drift."


Some user comments:

"we owe Gabriel a lot of credit for this fantastic product. The NanoVNA -QT work also great for a full S11/S22/S21/S12 measurement by capture S*1. and swapping the DUT direction while capture s*2 and then exported to a S2p file. Both the s1p and s2p files are to import in NanoVNA saver as a measurement of a background so the limited scale settings for the NanoVNA-QT are easy to cope with.

"A quick sniff test from 0.1 to 900MHz sweeping a 26cm long rigid UT141A line show extremely accurate calibration by using nothing as open, a truly 0 ps short from Fairview microwave and the male load from my HP85033C 3.5mm calibration kit. So all in all a quality calibration kit"

"Gabriel Tenma White wrote:
... I got message from the seller that they are frustrated with selling direct. One user for example wrote a negative review saying it didn't arrive only 24 days after buying, while it clearly says on the website that the expected shipping time is 25 to 45 days and probably longer due to covid-19, with a promise to refund or reship if it's not delivered in 60 days. They reply to all messages on time and yet there are reviews saying they don't reply to emails. ..."


Performance reviews have been universally positive for a 3 GHz sub $100 VNA. Its hard to criticize a device with that kind of price to performance ratio. The negative reviews have been along the lines of the last user comment and are not in regards to performance but shipping time, which during the COVID-19 crisis is rather unavoidable.

- Herb

CT2FZI 2020/04/29 18:29

Thank you so much for sharing your experience and this compilation.

The SAA-v2 its a gem. For the price tag its virtually impossible to find a
device so accurate and with so many resources. I think, once nanoVNA-Saver
is fully compatible it will be a killer VNA :D

Cheers!


*73 de Luís, CT2FZI*

*QRV @ 145.300 MHz | **CQ0VMST (VHF REP Monsanto)*
<http://goog_717545661>
http://www.ct2fzi.net


<http://goog_717545661>


On Wed, 29 Apr 2020 at 17:33, hwalker <herbwalker2476@gmail.com> wrote:

hwalker 2020/04/30 06:28

One hardware related issue I forgot to mention in my NanoVNA-V2 one month review is its use as a CW signal generator. User John Gord posted, "The NanoVNA-H can be used as a simple signal generator in CW mode. The NanoVNA-V2 can not, since the port 0 switch is changing during each measurement. A nice addition to the firmware would be a no-measurement signal generator CW mode that just provided a constant output."

Port 0 is switched on and off to provide ECAL temperature stabilization. When the NanoVNA-V2 is used as a CW generator this results in a signal that is switched on and off rather that having a constant output. Depending on your application, this may or may not be relevant.

- Herb

ok1vaw 2020/06/14 03:47

I will agree it will be nice too to have a possibility to to use NanoVNA V2 as a CW generator. The continuous switching on and off resulting of with 1MHz wide AM modulated signal. Do not tell me, that it is necessary to look on the ECAL every 30ms.
Vojtech.

Wouter van Gulik 2020/06/16 00:03

I am thinking about improving the situation with ECAL while using the device as a CW generator. However Gabriel states this will probably make the S11/S21 readings less accurate. Note that the ADF4350 requires a decent amount of energy and thus warms up which tend to influence measurements, hence the ECAL.

So I was thinking about using CW mode for a "CW tone and no ECAL" and a zero span as "CW with ECAL". Since in zero span you might be interrested accurated S11/S21 data?

Does that sound reasonable?

Wouter van Gulik 2020/06/16 00:13

Some more feedback:
- Battery status is only available on the LED, not on the screen. This make it hard to read if in a case.
- The backlight is not software controllable.

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