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Using guidance from various kind people on issues with the power supply I was able to modify nanoVNA to enable the first real measurements at 2GHz.

Measurements are done WITHOUT averaging, only some more points so it is easier to see the noise levels. You will get the same results on a standalone nanoVNA

The first picture is a scan of S21 from 1.9GHz till 2.1GHz of a 20MHz BW 2GHz cavity filter
There is still a level problem as the loss of the filter is for sure less then shown. Dynamic range is a bit more than 20dB. Did not try yet if an amplifier after the filter will help

The second picture is a scan of a 25 ohm resistor that clearly shows what to expect in the future.
From 1.6GHz till a bit above 1.7Ghz the bridge stops working. Above 1.7GHz the SNR is bad but with some averaging possibly will be workable.
Now I need a 2GHz antenna for further testing.

Hope this will inspire people to explore and expand the performance boundaries of this wonderful little device.

Yes. It's a blob of noise with some wild lines around it at 25 + j0 ohm
As it is difficult to observe frequency in a Smith chart I assumed showing both R and jX would be simpler.

On Sun, Oct 13, 2019 at 08:27 PM, <erik@...> wrote:

I was able to modify nanoVNA to enable the first real measurements at 2GHz.

What is your modification exactly?

Changed the offset from 5kHz to 12kHz and running the nanoVNA directly from a linear 5V power supply. Even with USB connected the latter makes a substantial difference in noise levels
Guess adding some inductors to the nanoVNA to block VHF/UHF supply noise is the next step