[Amps] Low efficiency on 160 m

[Markku Oksanen]

All

I have a GU-78 amplifier based on the Russian R-140 military station.
It turns out that the efficiency is low on 160 m and I suspect that the tank circuit Q is low on 160 m.
However I am not sure if this is the cause.  The tank circuit Q is not high, that I can tell from the capacitor values.

Another symptom of non-optimal loading is that the screen current is negative unless I really push the drive to very high output and very close to having grid current.

I have tried to look for information about low Q tank circuit problems but no luck so far.

Markku
OH2RA/OG2A/WW1C