Hi Vic,
A 4-400A is just a 4-250A with a larger plate structure.
It is an emission limit.
73 & Good morning,
Marv WC6W
http://qsl.net/wc6w/
******************************
--- On Sun, 5/8/11, Vic K2VCO <vic@rakefet.com> wrote:
> From: Vic K2VCO <vic@rakefet.com>
> Subject: [Amps] 4-400A ratings
> To: "Amps reflector" <amps@contesting.com>
> Date: Sunday, May 8, 2011, 11:01 PM
> 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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