[Amps] 4-400A ratings

[Roger (sub1)]

On 5/9/2011 11:33 AM, Vic K2VCO wrote:
> 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!

There are rare times when even a db can make the difference.

73

73

Roger (K8RI)
> 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.