On Mon, 02 Nov 1998 05:18:12 EST wb8jkr@juno.com (Mark S Graalman)
writes:
>
> I remember that article well! The thing used two
>vacuum variables on each pi network, can you
>IMAGINE the cost today! It was in ham radio magazine,
>about 71-72 I think.
>
>Mark WB8JKR
>
>On Sun, 01 Nov 98 21:48:44 PST "doshhan" <doshhan@vaxxine.com> writes:
>>
>>
>>
>>I have an old QST article (maybe it was HRM) from the 70's called
>'The Ecology Linear amplifier' where the author did just what you're
>>thinking about. A single 4-1000 feeding 5 or 6 separate Pi tanks. He
>>used some weird scheme with a telephone dial to switch the tanks in
>>and out as he changed bands.
>>
>>Phil T
>>VE3OZZ
Break... Break...
The article is in March 1972 Ham Radio pp.6-15.
It is actually not as absurd as it might seem in dim memory.
There were only 4 vacuum caps in that unit for the plate tuning of
the higher bands. The 10M cap was fixed and the load caps were air
variables plus appropriate padders.
Of course there were only five bands in those days. I don't think
that this is a valid approach in the 90's
The author also mentioned having to deal with some interaction
between all the coils in this conglomeration. I sure would hate to go
to all that work, he reported that it took 800 hours to construct, to
create some unique problems!
I also vaguely recall another amplifier that did employ vacuum caps
at both spots in all 5 output networks but, I think that it was almost
certainly done by someone at Jennings. :-)
73,
Marv WC6W
*
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