[AMPS] SB-220 conundrum

[Vic Rosenthal]

Pete Smith wrote:
> 
> 2.  But on 40m, power output (PLATE and LOAD tuned for maximum) is ~1450w,
> grid current ~250 ma. and Plate current ~900 ma.  There is also a fairly
> striking difference between the PLATE setting in this condition and the
> setting for minimum plate current.  If I tune the PLATE for minimum plate
> current and LOAD for maximum output, the figures look much more like those
> on the other bands.

An off-the-wall guess:  I recall that with grid-driven amps, a big difference
between the point of minimum current and maximum output was often indicative of
improper neutralization -- in other words, feedback from the amp's output to the
input.  Perhaps in changing the relays, you did something which increased the
output-to-input coupling.  Is the braid of the coax from the input relay to the
cathode circuit grounded at both ends?  I could imagine some kind of stray
resonance in this cable...

73,
Vic, K2VCO
Fresno CA

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