Hi Alex,
I'd have to re-check the circuit, & that'd mean digging-up that old QST from
my archives...
I was SO put off by the notion of that 120-watts of drive, I guess, that
mentally I stopped looking at the thing in any detail right then & there! Hi
Hi.
~73~ Eddy VE3CUI - VE3XZ
***********************************
----- 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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