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Re: [Amps] 8877 cathode impedance

Subject: Re: [Amps] 8877 cathode impedance
From: Vic K2VCO <>
Date: Tue, 27 Nov 2012 15:00:54 -0800
List-post: <">>
I'm using an attenuator like that in my grid-driven 813 amp. It provides a reasonable drive level as well as improving the SWR seen by the exciter. It's important to heat-sink them well because they dissipate a lot of power in a small spot.

On 11/26/2012 4:36 PM, Steve Bookout wrote:
Hello all,

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.

Also, thinking attenuating the drive power AFTER the T/R relay and before the 
matching network.  Right now it only takes 22 watts for 1500 out at 4 KV.  A 
bit touchy to tune (only been like that for 27 yrs.)  Would be nicer to tune at 
60, or so, watts out.  I saw where Henry radio has some attenuators on Ebay 
that might fit the bill.


73 de Steve, NR4M

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Vic, K2VCO
Fresno CA

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