Amps
[Top] [All Lists]

Re: [Amps] 8877 cathode impedance

To: Amps <amps@contesting.com>
Subject: Re: [Amps] 8877 cathode impedance
From: Bill Turner <dezrat1242@yahoo.com>
Date: Tue, 27 Nov 2012 16:35:50 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
ORIGINAL MESSAGE: 
On Mon, 26 Nov 2012 19:36:21 -0500, Steve wrote:

>Want to re-do the input matching of an old HB 8877 amp.  What should I use for 
>the cathode impedance when calculating my pi network?  I recall it was 
>something like 50-60 ohms.

REPLY: 
The cathode impedance is close enough you don't need any impedance matching. I
built my homebrew 8877 amp with only a simple parallel resonant circuit in the
cathode circuit to provide the 'flywheel' effect needed for good IMD. I used a Q
of five on all bands. Each band has it's own small toroid coil and a mica
compression trimmer for tweaking. 

Works great on all bands except 160 and 80 meters where I have to turn on the
tuner in the transceiver at the high end of the band. The other bands are flat
enough across the whole band.

If I were doing it over I would also install a trimmer capacitor adjustable from
the front panel for fine tweaking. 

73, Bill W6WRT
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps

<Prev in Thread] Current Thread [Next in Thread>