Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site mgweed.UUCP 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