On Sat, Dec 7, 2019 at 03:54 PM, Kurt Poulsen wrote:
Regarding the impedance issue i did look at the phase oscillation from 0.5 to
500MHz when I in the ZPLots has subtracted the length where the Phase
approaches a straight line with oscillations. Then I change the ZO on either
side off 50 ohm in steps of 0.1 ohm and for 51.4 ohm the phase oscillation was
minimized. The return loss oscillation is not changed by changing the Z0 but
rather due to port mismatch.
Hello Kurt,
Thank you very much for your quick answer.
I have 3 questions:
1. Where did you subtract the length (20 cm) ?
2. Did you mean that the S11 phase oscillation curve (about sinus) horizontal center line
should be minimised to a straight line and not be bowed?
3. Did you mean with the change of Z0 to connect a resistor of 50 Ohm
at the end of the 22 cm coax cable? And then vary this resistor in 0.1 Ohm steps
to minimise the amplitude of the phase oscillation amplitude?
I mean your file "NanoVNA supplied cable 50K to 500MHz.png" in post 7877 at 2019-12-05 20:10.
In this screen shot there are 2 diagrams with S11 Phase.
When I try to get a similar diagram with a 30 cm RG174 coax cable with open end
I get see attached screen shot nanoVNA-saver_RG174-30cm-open-end.png
73, Rudi DL5FA
