Hi Ron,
here are the graphs with Return Loss and Z, plus also two markers above
and below the frequency of resonance:
https://drive.google.com/open?id=1SGQP9o7CZHm7UfXB0Fk31Nce3_TA_0Eo
https://drive.google.com/open?id=1Bp1VLDjcnb5wGVVBCMHjNGkmwvZgQkN4
https://drive.google.com/open?id=1hWDKsd51tpFTfHuoWapJ2M1t1OBAdBjA
I'm suspecting that some component, probably capacitors, have different
behavior with and without voltage applied; this could explain the
perfect match with VNA and the mismatch transmitting...
Here is also the schematic diagram of the PA with driver:
https://drive.google.com/open?id=1cWJJ90h-cEa7J54KZOB6NWDmS7HIFM4b
Thanks and 73
Guido, ik2bcp / k2bcp
Il 15/05/2019 13:40, Ron Youvan ha scritto:
Hi Guido Tedeschi:
First of all, thanks to everybody for the answers.
/* snip*/
4) I connected again the VNA, this time directly to TX SO239 with the
antenna relay manually closed, and a 2200 ohm resistors between tubes
plates and ground: I was able again to tune the PI network for 50 ohm
on VNA on 80, 40 and 20m with plate and load capacitors set to
"normal" positions, only on 40m the plate is a little outside of the
mark.
Here follow some pictures:
I think your recorded graphs would be more useful if you put RL on the
left hand trace and impedance on the right hand trace.
Knowing if these two are changing sharply or gradually can be
significant.
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