[Amps] 8877 cathode impedance

[Jim W7RY]

Sounds like you need more like 6dB. That would be 88 watts of drive 
required.

73
Jim W7RY


-----Original Message----- 
From: Steve Bookout
Sent: Monday, November 26, 2012 4:36 PM
To: amps at contesting.com
Subject: [Amps] 8877 cathode impedance

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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