Return-Path: Received: (qmail 27615 invoked from network); 11 Jan 2004 15:50:19 -0000 Received: from unknown (HELO ptb-mxscan03.plus.net) (212.159.14.237) by ptb-mailstore02.plus.net with SMTP; 11 Jan 2004 15:50:19 -0000 Received: (qmail 39401 invoked from network); 11 Jan 2004 15:50:19 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 X-Priority: 3 X-MSMail-Priority: Normal Received: from ptb-mxcore03.plus.net (212.159.14.217) by ptb-mxscan03.plus.net with SMTP; 11 Jan 2004 15:50:17 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1Afhqz-000A8R-KZ for dave@picks.force9.co.uk; Sun, 11 Jan 2004 15:50:17 +0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1AfhqM-00007K-02 for rs_out@blacksheep.org; Sun, 11 Jan 2004 15:49:38 +0000 Received: from [194.25.134.84] (helo=mailout09.sul.t-online.com) by post.thorcom.com with esmtp (Exim 4.14) id 1AfhqL-00007B-9f for rsgb_lf_group@blacksheep.org; Sun, 11 Jan 2004 15:49:37 +0000 X-Fake-Domain: fwd02.aul.t-online.de Received: from fwd02.aul.t-online.de by mailout09.sul.t-online.com with smtp id 1Afhop-0001zg-00; Sun, 11 Jan 2004 16:48:03 +0100 X-Fake-Domain: (VaiplaZpreui8YlKgkJcyFg7xB20Hj8+5kKcDjBjptOWjCDhb30tc1@[62.224.51.236]) Received: from (VaiplaZpreui8YlKgkJcyFg7xB20Hj8+5kKcDjBjptOWjCDhb30tc1@[62.224.51.236]) by fwd02.sul.t-online.com with smtp id 1AfhoZ-0nASBc0; Sun, 11 Jan 2004 16:47:47 +0100 From: "jannsen" <0482183881-0001@t-online.de> To: rsgb_lf_group@blacksheep.org References: <200401111221.i0BCLgQ13690@mailgate5.cinetic.de> X-Mailer: T-Online eMail 2.34 MIME-Version: 1.0 Date: Sun, 11 Jan 2004 16:47:47 +0100 Message-ID: <1AfhoZ-0nASBc0@fwd02.sul.t-online.com> X-Seen: false X-ID: VaiplaZpreui8YlKgkJcyFg7xB20Hj8+5kKcDjBjptOWjCDhb30tc1 Subject: Re: LF: 300W-TX-G0MRF 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-Level: ** X-Spam-Status: No, hits=2.4 required=5.0 tests=FROM_ENDS_IN_NUMS,FROM_STARTS_WITH_NUMS 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 Hans-Albrecht Haffa schrieb: > Dear Peter, > > I have had similar problems in constructing PAs. > > > First: One reason for the ringing might be the transistors. Put a capacitor > 2n7/ 3kV ceramic from > drain to source at each PA-transistor. This is likeliy if the pa is operated > with an quiescent current. > > sec.: If You dont have any quiescent current at all, than there is no damping > resistor at the transformer for the winding that is not driven . Any > winding of a transformer that carries no current will ring. This effect has > been never described in amateur radio . The only thing You can do against is > adding an quiescent current or using an topology where all windings carry > allways a current, that is only two windings, pri and sec. > > More upon request. > Hans-Albrecht Haffa > DK 8 ND > CBA, ++49-(0)7161 - 87847 > Hi Hans, the problem Peter has with the T2 of the G0MRF PA (here with four MOSFETs) I have had too. 1.no current in the quiescent state. 2.all windings carry current during transmission. 3.if I operate the PA in up to 200W mode there is no ringing (no vibration). 4.if I operate the PA in 600W mode there is no ringing in the first two minutes of operation. after two minutes the ringing begins accompanied with reduction of output power (permeability loss depending on temperature I guess). All problems have been solved by cooling the T2. btw. the output transformer of my other PA (up to 800W) consists of four toroids Philips RCC36.6/15.6-4C 65, Al3000, color grey. absolutely no ringing problems or losses when getting hot! best regards Uwe/dj8wx