Quoting Patrick Barthelow <apolloeme@live.com>:
> If say, the Modulators were dissapating 400 watts each, and bright
> orange, how many watts, would you guess the RR PAs were dissapating?
Class A ( modulators running less than 50% efficiency )
With zero modulation, they are going to always show some color
Full modulation they will get bright.
Class C ( RF amps in AM service ) running 70% efficiency
with zero modulation, will turn grey.
Plate voltage on the RF tubes vary from 1 x hv with no modulation
and between 0 x hv to 2 x hv depending on modulation percentage.
Trying to run a full killowatt in AM commercial service in the 60s
with a quad of 4-400s ... You had to replace the tubes every 12 months
@ $200 for the four.
They were standing on their tip-toes to make a KW out, but tubes were cheap.
The RFs would last a couple of months longer than the modulators.
Really cheap stations would move the RF tubes to the modulators and
put in new $100 RF tubes and get another couple of months service
before modulation would drop below 90%.
To answer the question, if the modulators were dissipating 400 watts,
the RFs were probably averaging 300 watts per tube.
Don W4DNR
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