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Re: [Amps] 8877 cathode impedance

To: "Steve Bookout" <steve@nr4m.com>, <amps@contesting.com>
Subject: Re: [Amps] 8877 cathode impedance
From: "Jim W7RY" <w7ry@centurytel.net>
Reply-to: Jim W7RY <w7ry@centurytel.net>
Date: Sun, 2 Dec 2012 21:56:46 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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@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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