With 3KV, plus enough drive and screen voltage you will have a hard time
keeping them under 400 ma at full load. All they need is air to stay happy.
Carl
KM1H
----- Original Message -----
From: "Vic K2VCO" <vic@rakefet.com>
To: "Amps reflector" <amps@contesting.com>
Sent: Monday, May 09, 2011 2:01 AM
Subject: [Amps] 4-400A ratings
> I've come into a pair of 4-400A's. I'm thinking about building an
> amplifier with one tube
> and using the other for a spare. Looking at the data sheet for class-C CW,
> the maximum
> rated plate current is 350 ma. This means that at 3 kV on the plate I can
> expect to get
> only about 750-800 watts output. This does not come close to utilizing the
> 400-watt plate
> dissipation of the tube.
>
> At 4 kV, I could get 1400 watts input and about 1050-1100 out. That's a
> lot better. But it
> means a lot of extra expense -- the power supply, tuning capacitor, etc.
> need to be bigger.
>
> Is this correct? Why is the plate current limited to 350 maA? Is it a
> limitation on
> filament emission?
>
> Of course I can use both tubes and get full legal power. But then I need
> another socket,
> chimney, etc. Or maybe I can use the "SB220 cooling method" and cheaper
> sockets.
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
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>
>
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