Also use at least 3 kv, this isnt the 1000W input days and efficiency is
improved to the point that a pair of 304TH's will approach 10dB stage gain
in GG.
OTOH, Id be more inclined to run them grid driven in parallel if drive is
limited to 100W. Swamp the drive a bit to minimize or even eliminate the
need to neutralize. The grid bias requirements are well within reason..
One thing about that tube is that it has beaucoup emission reserve and can
be pushed well above its ratings in SSB and maintain linearity. It needs
some good air flow however.
Carl
KM1H
----- Original Message -----
From: "Alex Eban" <alexeban@gmail.com>
To: "'Edward Swynar'" <gswynar@durham.net>; <amps@contesting.com>
Sent: Sunday, September 06, 2009 2:30 AM
Subject: Re: [Amps] The H&K 304H
>A question: does the H&K incorporate an input tank circuit. If not adding
> one will improve the gain. Grounded grid tubes are known to have
> comparatively low gain, so that every improvement in matching is
> worthwhile.
> Besides, remember that a gain of about 8-9 dB is about reasonable for such
> a
> setup- even the 4-1000 is about that figure- more than that requires a
> high
> level of elaboration. On the other hand keep in mind that a sizeable
> portion
> of these 120 watts are transferred to the output, so it's not a total
> loss.
> Alex 4Z6KS
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Edward Swynar
> 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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