I have a short length of coax on the CH0 channel to make using the VNA easier. I calibrate everything with that cable, but the phase is never zero. Ok, it probably can go to zero but not when I think it should.

Shouldn't calibration reset phase too.

On Tue, 18 Feb 2025 12:58:02 -0800
"Leif M via groups.io" <leif.michaelsson=gmail.com@groups.io> wrote:

> I have a short length of coax on the CH0 channel to make using the
> VNA easier. I calibrate everything with that cable, but the phase is
> never zero. Ok, it probably can go to zero but not when I think it
> should.
>
> Shouldn't calibration reset phase too.

The phase will probably only be zero at the end of the cable with a
calibration open piece fitted (this extends the shield along the plane
of the centre pin to ensure that the E-field all terminates on the
shield), you are seeing the effect of the capacitance of the pin to the
shell plus the self inductance of the pin, the reference plane is
effectively where the dielectric ends. This effect is less noticeable
if the cable ends in a female connector rather than a male connector.

--

Brian Morrison

I tried with open calibration piece, and the phase is indeed very close to zero. Than you for the advice.