Return-Path: Received: (qmail 22151 invoked from network); 11 Jan 2004 18:15:58 -0000 Received: from unknown (HELO ptb-mxscan03.plus.net) (212.159.14.237) by ptb-mailstore01.plus.net with SMTP; 11 Jan 2004 18:15:58 -0000 Received: (qmail 75729 invoked from network); 11 Jan 2004 18:15:57 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Priority: 3 X-MSMail-Priority: Normal X-Spam-detection-level: 11 Received: from ptb-mxcore03.plus.net (212.159.14.217) by ptb-mxscan03.plus.net with SMTP; 11 Jan 2004 18:15:56 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1Afk7w-000Jaa-OQ for dave@picks.force9.co.uk; Sun, 11 Jan 2004 18:15:56 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Afk7b-0002ga-8J for rs_out@blacksheep.org; Sun, 11 Jan 2004 18:15:35 +0000 Received: from [205.188.157.35] (helo=imo-d03.mx.aol.com) by post.thorcom.com with esmtp (Exim 4.14) id 1Afk7Y-0002gR-Ef for rsgb_lf_group@blacksheep.org; Sun, 11 Jan 2004 18:15:32 +0000 X-Fake-Domain: G0MRF@aol.com Received: from G0MRF@aol.com by imo-d03.mx.aol.com (mail_out_v36_r4.8.) id l.1df.172b4482 (16109) for ; Sun, 11 Jan 2004 13:14:57 -0500 (EST) Received: from aol.com (mow-m06.webmail.aol.com [64.12.184.134]) by air-id12.mx.aol.com (v97.14) with ESMTP id MAILINID121-3eed400192a12e9; Sun, 11 Jan 2004 13:14:57 -0500 Date: Sun, 11 Jan 2004 13:14:57 -0500 From: G0MRF@aol.com To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 Message-ID: <5047BBB4.205C80C5.0000CE2C@aol.com> X-Mailer: Atlas Mailer 2.0 X-AOL-IP: 195.93.34.8 Subject: Re: LF: T2-ringing Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.3 required=5.0 tests=NO_REAL_NAME autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 1 In a message dated 1/11/2004 12:30:03 PM Eastern Standard Time, dj9dw@t-online.de writes: > nonconducting side. Eather a steady current and heat on the > FET's or by > adding a cap from D to G. This may be a mistake, but please remember you may have peaks to 200V on the drains and a limit of 20V (ish) on the gates. Any capacitor as suggested will destroy the devices in an instant. I have seen a few 'mods' including a zobel network i.e. a capacitor and resistor in series between drain and ground. This does de-Q the circuit quite well. Changes in value of the normal drain to ground 10nF will have some effect but it's likely to change any resonant frequency without reducing the Q or the total peak voltage. Bob G8RW ran his unit at over 300W and had installed 'transorbs' that conducted just below the max drain limit of the FETs. However, Bob's just had a single peak at the switch on / off points and not the 'ringing' described here. It may be worth looking at the T94-2 core / decoupling caps as well if ringing is at 1MHz+ 73 David G0MRF