There are some running 813's at over 3kv daily on AM; I didnt ask if it is
graphite or tantalum plates. I run close to that with graphite plates and
never a hiccup.
IMO, the 813 is a highly underated tube and Pd with a bit of air is easily
250W.
I remember reading something about 304TL/TH IMD years ago and it wasnt very
good except in AB1 where it was in the high-20's which is about the same as
most ricebox rigs. Then the PEP was limited to 300-400W iffn I remember.
Sounds like some modern testing is needed.
Carl
KM1H
----- Original Message -----
From: "John Lyles" <jtml@losalamos.com>
To: <amps@contesting.com>
Sent: Monday, September 07, 2009 10:37 AM
Subject: [Amps] 304TH, 304TL, 813
>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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