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Path: utzoo!watmath!clyde!burl!mgnetp!mgweed!rjr
From: rjr@mgweed.UUCP (Bob Roehrig)
Newsgroups: net.ham-radio
Subject: Amplifier filament choke question
Message-ID: <11423@mgweed.UUCP>
Date: Fri, 10-Aug-84 12:09:49 EDT
Article-I.D.: mgweed.11423
Posted: Fri Aug 10 12:09:49 1984
Date-Received: Sat, 11-Aug-84 00:34:51 EDT
Organization: AT&T Consumer Products - Montgomery Illinois
Lines: 18


I am going to modify an old grid-driven power amplifier, which has a
pair of 4-400A's, to a grounded grid input. Has anyone used toroidal
cores such as the Amidon T-200 (commonly used for baluns) for a
filament choke? Most all units I have seen use a ferrite rod for this.
I want this amp to go down to 160 meters.

Many years ago I built an amp using a single 4-400A and used a rod for
the choke. To get enough inductance to be effective on 80 meters,
I had to wind 3 layers of wire on it and the wire had to be at least
no. 10 to keep the voltage drop at a minimum. 

My old Hallicrafters "Loudenboomer" amp uses a tap on one winding
of their choke to get a proper impedance match and I hope to do
the same thing to eliminate the need for any input tanks.

Bob K9EUI