THE COMMAND TECH HF-2500E THAT RUNS 3 3CX800 TUBES USES THIS UN-UN SYSTEM AND
AT 3KW OUTPUT THERE SEEMS TO BE NO ISSUES WHATSOEVER. Seems to be a tried and
true design. It's hard to argue with success like that.
-----Original Message-----
From: Jim Barber <audioguy@q.com>
To: Amps <Amps@contesting.com>
Sent: Sun, Oct 20, 2013 3:31 pm
Subject: Re: [Amps] 200-ohm tank and "un-un" in HF amp design?
Thanks for the replies.
Notables are:
(1) Higher loading cap voltage (Gold Star Winner)
(2) Loss, and what to do with the heat
(3) Cost
Thanks and 73,
Jim N7CXI
---------
Assuming adequate core/wire sizing and airflow, can anyone think of a
solid reason *not* to design a legal-limit HF amp output tank for 200
ohms, then use a 4:1 "un-un" transformer to step it down to 50?
I'm curious because doing so would bring the loading cap requirement for
a 4000-ohm plate impedance down to under 1000pF at 1.8 mHz, which can be
done with a large air variable alone.
Note: Yes, I know it *has* been done already, but I'm asking for
opinions as to whether you think it should be.
Thanks and 73,
Jim N7CXI
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