I picked up an old copy of Don Stoner's (W6TNS) New Sideband Handbook,
dated 1958, CQ Technical Series, at a hamfest last month. Interesting
reading, the Heathkit SB10 adapter was hot stuff then, along with the
Central Electronic 10B and lots of Command set conversions.
The amplifier chapter is fun reading. There is a section on using
surplus tubes, such as the 304TL and the Western Electric 701A radar
pulse tube on the low bands. For the TL in GRID Driven application, the
drive power is said to be 15-20 watts PEP for 550 watts output. It has a
step up input resonant circuit and a link coupled output with split
stator cap. Classic stuff! The book has excellent references in each
chapter, with a footnote pointing to Leary's article in Jan. 1955 QST,
"Grounded Grid and the 304TH".
An interesting section includes grid-driven 813 amplifiers using a clamp
tube such as 6L6 or 6Y6 on the screen, the ZL1AAX and G2MA amplifiers.
This stuff seems to have gone away for the most part, along with the
need for neutralization circuits. Stoner wrote that 813 could take up to
3000 VDC with adequate bias voltage.
73
John
K5PRO
>> Sent: Saturday, September 05, 2009 5:32 PM
>> To: amps@contesting.com
>> Subject: [Amps] The H&K 304H
>>
>> Many thanks to all who took the time to respond to my query about the old
>> Heintz & Kaufmann 304H (their version of the Eimac 304TH, per Lud's note
> to
>> me)...
>>
>> Well, research into my radio shack library here revealed that the 304H is
>> most certainly NOT a good candidate for grounded-grid service: a piece in
> a
>> 1954(?) issue of QST described just such an arrangement, & stated that for
> a
>> kilowatt (approx.) input, a single g-g 304H would need 120-watts of drive!
>>
>> Hardly promising.
>>
>> However, I did take heart when thumbing through my 1980 edition of the
> ARRL
>> HANDBOOK: there's an interesting low-band "junker" design listed therein
>> that incorporates a grid-driven 833A. The article makes mention of the
>> possibility of using a 304TH in its stead, & published specs say that such
>> an arrangement would need but 30, or so, watts of drive...ideal.
>>
>> As I mentioned to Lud, I could lash together a robust enough filament
>> voltage provider that would easily power up either an 833A, or a 304H:
> then,
>> with the filament "sockets" paralleled, and allowances made for room, I
>> could run either tube in the circuit, as dictated by availability &
>> interest...
>>
>> ...One tube at a time, of course!
>>
>> ~73~ Eddy VE3CUI - VE3XZ
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