Hello Mito,
In the differential mode how will that internal common ground affect
measurements as it will effectively short the current that is supposed to
go through the shield of the coaxial cable making the balun?
Now I have internally bonded ground between shields at Port 0 and Port 1,
and i ALSO have shield of the coaxial cable connecting grounds of those two
ports!!! THAT DOES NOT SEEM RIGHT!
I see sometimes a transformer when measuring the differential mode:
; DM Measurement
b).
I though don't think this solves your question... So you have a good
question.
All the best,
Victor
Op do 7 jul. 2022 om 22:26 schreef Miro, N9LR via groups.io <m_kisacanin=
[email protected]>:
Found several articles and several answers/opinions on this topic :)
If I want to do 2 port measurement in a setup where the input and output
of the DUT do NOT have common ground (let's say an RF transformer, or a
simple current balun), how will internal common ground on nanoVNA ports
affect measurements.
Let's be even more specific - want to do some simple testing of an HF
balun. S21 for differential mode and for the common mode suppression. Just
for the sake of the argument, balun will be wound with a short (comparing
to lambda) piece of coaxial cable, either wound in air or on ferrite toroid.
In the CMR mode I'l short both sides of the balun, connect to "hot" ends
of both nanoVNA ports, and "rely" on the grounds being connected internally
- is that correct setup?
In the differential mode how will that internal common ground affect
measurements as it will effectively short the current that is supposed to
go through the shield of the coaxial cable making the balun?
So, in one case (CMRR measurement) that internal common ground helps. but
in the other (differential) it does not.
All would be easier if ports on nanoVNA are not bonded internally and I
have an option to connect them or not :)
