ATS-MINI Input Impedance Test

[G8PTN]

Hi,
I suspect the input impedance results for the ATS-MINI V4 may be invalid.

The drive level from the VNA may be forward biasing the ESD protection diodes?

When measuring the impedance of a receive front end, try an attenuator pad, and then calibrate with SC/OC/50Ω on the output of the pad.

The following YouTube video describes a similar problem when measuring a low signal amplifier. In this case the problem was that the impedance was reading higher than expected.
https://www.youtube.com/watch?v=7TtKE39TWpI

It is not clear from the images what the diode is on the screen side of the PCB near the antenna connector.

Perhaps the cause is not the VNA levels, but it seems strange that the input impedance is so low, considering a JFET buffer has been used on the front end.

Alternatively there is a wrong component or wrong value fitted somewhere?

73, Dave