[Amps] 8877 cathode impedance

[Vic K2VCO]

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.
>
> http://www.ebay.com/itm/New-250-Watt-4-dB-50-ohm-Hybrid-Attenuator-up-2-GHz-/390408415503?pt=LH_DefaultDomain_0&hash=item5ae627a90f
>
> Comments?
>
> 73 de Steve, NR4M
>
>
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/