[VHFcontesting] 222 amp

Dave Olean k1whs at metrocast.net
Wed Dec 31 08:19:40 EST 2014

I show very little grid current. Roughly 3000 volts .500 mill of plate 
current 1500 in 200 out. 20-25 watts drive Ft736 driver. Mike

Those readings seem ok. I would think that 20 watts would drive it to 500 
ma. I would make sure that you could move the plate loading "plate" far away 
from the tube. Are you sure that the plate circuit goes thru resonance? 
Maybe it never does! You might check that too. Use a grid dipper or antenna 
If the loading control has little effect, I would also try looking at the 
input with some sort of return loss bridge or antenna analyzer. You could 
also put a Bird 43 type instrument in and see what the VSWR looks like when 
you apply drive power. I remember I had a problem with my new amplifier and 
it was a poor connection on a ground on the input circuit around the tube 
socket. The input impedance changes with drive level, so a VSWR check is 
only valid when the amp is being driven with RF, but you should still see 
some sort of poorer match with almost no drive.

Dave K1WHS

----- Original Message ----- 
From: "mike repinski via VHFcontesting" <vhfcontesting at contesting.com>
To: <vhfcontesting at contesting.com>
Sent: Wednesday, December 31, 2014 4:16 AM
Subject: [VHFcontesting] 222 amp

> One other observation. The controls do not seem to operate as sharp as my 
> 2 meter amplifier does. Kind of sluggish. The loading does not seem to do 
> much. Mike WB8PFZ
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