> Rich writes:
>
>> P = I x E comes pretty close.
Joe writes:
> That's fine but as I said: "I don't have the constant
> current curves"
> which means I do not have any way to determine the peak
> (or even
> average through the full RF cycle) cathode to grid voltage
> in the
> 3CX1200A7.
At 2000w out with 120W of drive and 250mA of indicated Ig,
grid dissipation is only about 30W with a peak emission
current at the crest of the cycle of about 4 amps.
Contrary to authoritative guesses, the tube is well out of
emission saturation and remains much cleaner than any modern
exciter we can buy (with the exception of a class A operated
FT1000 MK V).
At 1700W and 200 mA Ig, grid dissipation is about 20 watts.
That's all at 3300V, things get much better at higher anode
voltage.
Keep the grid below 300mA and you are OK, although I'm sure
even going well over 50W won't actually hurt that grid. The
limit they set on this tube isn't due to grid failure, it is
where secondary emission sets in.
73 Tom
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