[Amps] Estimating CCS, I CAS, Plate Dissipation by Eyeball 4-400As

[donroden at hiwaay.net]

Quoting Patrick Barthelow <apolloeme at 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