Hi,
I want to report a possible issue in measuring the phase with NanoVNA V2. (or maybe just my clone do this ?)

I have an SAA-2N and I made a comparison with my older NanoVNA H, with the latest firmware. The SAA-2N has the V2.74 Blackmagic firmware installed. I must mention that the previous phase measurements with H were quite good, as expected, according to my knowledge about the phase change at the resonance of a quartz crystal. So the phase must have a shift at the series resonance and a rapid reverse flip at the parallel resonance.

I measured a 16 MHz quartz crystal and a "T" filter to see the difference between phase measurements and the results are in the images below:
- NanoVNA H sweeping the quartz crystal: H_quartz_1.jpg and H_quartz_2.jpg
- NanoVNA V2 sweeping the quartz crystal: V2_quartz_1.jpg and V2_quartz_2.jpg
- NanoVNA H sweeping the filter: H_filter_1.jpg and H_filter_2.jpg
- NanoVNA V2 sweeping the filter: V2_filter_1.jpg and V2_filter_2.jpg

Both H and V2 were calibrated with the same fixture and sweep frequencies.

In my opinion, there may be a problem in the phase measurements of V2.
Can anyone measure a quartz crystal to see if it will get the same results?

Thank you very much.

On Sun, Nov 29, 2020 at 05:22 PM, <hflorin@gmail.com> wrote:
>
> In my opinion, there may be a problem in the phase measurements of V2.
>
https://nanorfe.com/nanovna-v2-faq.html

the V2 is not suited to very narrowband measurements (coherent bandwidth <1kHz) because of the fast switching of the transmit and receive paths. In practice this only becomes a problem when measuring crystals (not SAW filters).

73, Rudi DL5FA

Does this mean that the v2plus (original or upgraded from v2) would be even less capable, in view of the increased sweep speed and therefore faster switching?

Steve L

On Sun, Nov 29, 2020 at 10:28 AM, Stephen Laurence wrote:

Does this mean that the v2plus (original or upgraded from v2) would be even less capable, in view of the increased sweep speed and therefore faster switching?
======================================================

Most likely, since you've noticed in on Gabriel's support forum that the issue has been raised with the V2plus4 also. Gabriel has acknowledged the issue and said that she is pondering a future firmware fix to address it.

- Herb

It looks like you are looking at CH 1 phase on the H, but CH 0 phase on the V2. Try changing the V2 Phase trace to CH 1.

--John Gord

On Sun, Nov 29, 2020 at 08:22 AM, <hflorin@gmail.com> wrote:

>
> Hi,
> I want to report a possible issue in measuring the phase with NanoVNA V2. (or
> maybe just my clone do this ?)
>
> I have an SAA-2N and I made a comparison with my older NanoVNA H, with the
> latest firmware. The SAA-2N has the V2.74 Blackmagic firmware installed. I
> must mention that the previous phase measurements with H were quite good, as
> expected, according to my knowledge about the phase change at the resonance of
> a quartz crystal. So the phase must have a shift at the series resonance and a
> rapid reverse flip at the parallel resonance.
>
> I measured a 16 MHz quartz crystal and a "T" filter to see the difference
> between phase measurements and the results are in the images below:
> - NanoVNA H sweeping the quartz crystal: H_quartz_1.jpg and H_quartz_2.jpg
> - NanoVNA V2 sweeping the quartz crystal: V2_quartz_1.jpg and V2_quartz_2.jpg
> - NanoVNA H sweeping the filter: H_filter_1.jpg and H_filter_2.jpg
> - NanoVNA V2 sweeping the filter: V2_filter_1.jpg and V2_filter_2.jpg
>
> Both H and V2 were calibrated with the same fixture and sweep frequencies.
>
> In my opinion, there may be a problem in the phase measurements of V2.
> Can anyone measure a quartz crystal to see if it will get the same results?
>
> Thank you very much.
>

Thanks a lot to John Gord and at the same time I apologize for the confusion created... Indeed, NanoVNA V2 starts with measuring the phase on CH0, that is on reflection (S11) and not on CH1 "through" (S21).

Thus, I was quite stupid to fall into the trap of not carefully checking the markers. So please excuse me for the confusion.

I attached the images with the correct phase measurement. So, pay attention to what is displayed on the screen! NanoVNA V2 does not start the same as NanoVNA H or H4.

Case closed. No issue.