[Amps] high sb-220 grid current - follow up ??

[Dan Sawyer <dansawyer@earthlink.net>]

All,

I posted here about an SB-220 exhibiting non-linear, hockey stick, grid 
current. This pattern starts at between 20 and 30 watts drive. This post 
is after gaining additional information.

My habit is to tune the amplifier with CW by 3 cycles of adjusting 
'tune' and then 'load' for maximum output power. This is done with 
increasing power up to about 400 watts output. This consistently results 
in a common 'tune' point and an almost identical 'load' point of 1 on 
the 'load' scale. If from this position drive is increased grid hockey 
sticks and pins the grid current meter.

Last evening during an SSB QSO I decided to 'tweak' the 'load' setting. 
To my surprise output power rose from 300 watts to 900 watts and grid 
current behaved normally. My observation after this re-tune was that 
grid current and plate current were linear; i.e. moving in unison. This 
is all on the low plate voltage setting. It is also my expectation for 
behavior.

I have now repeated this 2 more times so it is consistent. Now the 
questions:

1. What can cause the difference in behavior between tuning on CW and 
tuning on SSB?

2 Are there ways to tune duplicate this SSB tuning??

Thanks,
Dan





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