Or insulating material with high absorption at 2M
Carl
KM1H
----- Original Message -----
From: "Peter Voelpel" <df3kv@t-online.de>
To: <amps@contesting.com>
Sent: Monday, July 21, 2008 12:51 PM
Subject: Re: [Amps] Help with ARRL handbook design 4CX1000A 2m PA
>I built with those tubes a push-pull 2m amp many years ago, it was a
> quick&dirty design with efficiency at 58%.
> So the tubes do very well there.
> Is there something running hot in the output circuitry? Capacitors,
> stripline, coil etc.?
>
> 73 Peter
>
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Pete Lindsay
> Sent: Montag, 21. Juli 2008 18:43
> To: amps@contesting.com
> Subject: [Amps] Help with ARRL handbook design 4CX1000A 2m PA
>
> Hi Guys,
>
> I have a 2m PA built around the design in the 1986 ARRL handbook chapter
> 31
> using a 4CX1000A. It was built by a friend to a very high spec and looks
> like an exact copy of the original design. The problem is it has never
> really worked that well. The problem lies in the output efficiency which,
> at
> best, is only around 30-35%. I am using 3KV on the anode and have tried
> several tubes. The screen grid and control grid currents act as you would
> expect when increasing/decreasing the loading, but the output is just not
> there (measured on several different power meters). I would be very
> interested if anyone out there has successfully built one of these amps
> and
> managed to get a reasonable output efficiency. Other amps I have built
> with
> 8877/GS35 etc all work fine, but this one has me beat.
> Is there a critical part to the design which needs close attention to get
> it
> to work? Any help appreciated!
>
> Thanks
>
>
> Pete, G4CLA.
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