[Amps] 4-400A ratings

[Vic K2VCO]

I know. About 1.4 dB. Actually, I think 2 dB can make a difference on 160 meters. I don't 
know about 1.4!

I'm thinking that the "SB220 cooling system" would not work with these tubes because the 
metal base requires air to come up from below to cool the base seals.

On 5/9/2011 7:26 AM, Jim W7RY wrote:
> Get out your calculator and figure out how much of a dB/S-meter increase 1100 watts is
> above 800 watts.
>
> Then YOU can make the decision.
>
> 73
> Jim W7RY
>
>
> --------------------------------------------------
> From: "Vic K2VCO" <vic at rakefet.com>
> Sent: Sunday, May 08, 2011 11:01 PM
> To: "Amps reflector" <amps at contesting.com>
> 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/