[Amps] The 304H

[Carl]

I concur. Carbon plates take a lot of effort to degass (not always possible) 
and that assumes that the tube seals are still good and air is not mixed in. 
Bring the filament up on a Variac and see what happens for starters.

Great audio or Class C tube but not very efficient on SSB. What was called 
high mu in the 40's is nowhere near what is used today, they require a lot 
of drive to overcome the bias and for acceptable linearity Class AB is 
required.

Carl
KM1H



----- Original Message ----- 
From: <n8de at thepoint.net>
To: "Edward Swynar" <gswynar at durham.net>
Cc: <amps at contesting.com>
Sent: Tuesday, September 01, 2009 9:03 AM
Subject: Re: [Amps] The 304H


> In my estimation, it's not worth the effort, as those OLD tubes are
> probably quite 'gassy' from sitting around for so long.
> Good luck!
> Don
> N8DE
>
> Quoting Edward Swynar <gswynar at durham.net>:
>
>> Good Day All,
>>
>> A good Ham radio friend of mine recently blessed me with a donation
>> of three Heintz & Kaufmann 304H triodes (a near-carbon copy of the
>> Eimac 304TH, according to Lud Sibley)...
>>
>> Has anyone ever had any significant experience working with these
>> old-timers...? I've seen a circuit in Orr's handbooks, where a pair
>> of them were pressed into service as the p-p class-B final audio
>> amplifier stage of a legal limit AM modulator---but only one single
>> example in its use as a single-ended RF linear amplifier, in a 1954
>> CQ book on SSB techniques...
>>
>> I think it has distinct possibilities for a low-band kilowatt-plus
>> design---can anyone share their experiences in this regard with me...?
>>
>> Thanks in advance, & my vy
>>
>> ~73!~ Eddy VE3CUI - VE3XZ
>>
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