A small fan down below will take care of the filament pins and a SB-220
style fan on the glass. Be sure to ground the metal bas if going above 20M.
Im another that counts loss in tenths of a dB when adding up station
performance since anything not well above the noise level is usually not
worth working (-; Even the 160/80/75 combined inverted V is fed with 400'
of 3/4" CATV hardline.
Carl
KM1H
----- Original Message -----
From: "Vic K2VCO" <vic@rakefet.com>
To: "Jim W7RY" <w7ry@inbox.com>
Cc: "Amps reflector" <amps@contesting.com>
Sent: Monday, May 09, 2011 11:33 AM
Subject: Re: [Amps] 4-400A ratings
>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@rakefet.com>
>> Sent: Sunday, May 08, 2011 11:01 PM
>> To: "Amps reflector" <amps@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/
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>
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