Friends,
I have always been in admiration and awe to watch a Glass tube QRO Amp in full
song.
In the case of 4-400As or 3-500Z tantalum plates, wile being a teenager-ham, I
tended to wince a little at those two tubes showing what is probably long term
sustainable CCS plate dissipation.and usually backed off on drive to see a more
"dull red" tantalum (not talking here about carbon plates)
plate, which looked safer to me.
I found two good photos of 4-400As, commercial modulators, and an RF PA at
full song, or maybe at near, (conservative) full song. here:
Modulators; Bright Orange:
http://hawkins.pair.com/atcitynj/atcity14b.jpg
RF PA; Dull Red;
http://img153.imageshack.us/img153/7161/2collins20vtubeslitsize.jpg
I wonder if more seasoned eyes than mine could characterize these two photos
of 4-400A Tantalum plates.
If say, the Modulators were dissapating 400 watts each, and bright orange,
how many watts, would you guess the RR PAs were dissapating?
The Modulators are described as being at CCS dissipation ratings. Apparently
they could operate for years, 24/7 at that level. Is that true? or are they
being pushed, hard, and will live a shorter (how long) life?
The RF PA tubes, look to me to be more comfortable, more safe for long life.
Also, is there more wear and tear, that cuts into long term life in amateur
service, of the 3-500Z or 4-400A family, where the tubes, in correct SSB
service, or CW service, are dissapating widely varying power, according to duty
cycle and use? In SSB, to go from "cool, idle" to 2KW PEP and back several
times a minute, is that hard on the tube? I would guess they would be
happier in, say 1 or 2KW FM broadcast transmitter and staying orange 24/7 than
in amateur service. What say?
73, Pat Barthelow AA6EG
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