Return-Path: Received: (qmail 69331 invoked from network); 9 May 2004 20:25:22 -0000 Received: from unknown (HELO ptb-mxscan03.plus.net) (212.159.14.237) by ptb-mailstore02.plus.net with SMTP; 9 May 2004 20:25:22 -0000 Received: (qmail 61833 invoked from network); 9 May 2004 20:25:21 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 Received: from ptb-mxcore03.plus.net (212.159.14.217) by ptb-mxscan03.plus.net with SMTP; 9 May 2004 20:25:20 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1BMurQ-000Fl3-9N for dave@picks.force9.co.uk; Sun, 09 May 2004 21:25:20 +0100 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1BMupo-0000ih-2q for rs_out_1@blacksheep.org; Sun, 09 May 2004 21:23:40 +0100 Received: from [213.232.95.59] (helo=relay.salmark.net) by post.thorcom.com with esmtp (Exim 4.14) id 1BMupn-0000iY-Em for rsgb_lf_group@blacksheep.org; Sun, 09 May 2004 21:23:39 +0100 Received: from postbode03.zonnet.nl ([62.58.50.90]) by relay.salmark.net with esmtp (Exim 4.24) id 1BN1OC-0006Bj-J0 for rsgb_lf_group@blacksheep.org; Mon, 10 May 2004 04:23:36 +0100 Received: (qmail 30947 invoked by uid 10); 9 May 2004 20:23:27 -0000 Received: (vexira-qq 30894-3F5F66DA invoked from network) 09 May 2004 22:23:26 +0200 X-Fake-Domain: unknown Received: from unknown (HELO ibm) ([62.59.190.165]) (envelope-sender ) by postbode03.zonnet.nl (qmail-ldap-1.03) with SMTP for < >; 9 May 2004 20:23:26 -0000 X-Bad-Message-ID: no DNS (ibm) Message-ID: <001701c43602$1b335540$2102000a@ibm> From: "Dick" To: rsgb_lf_group@blacksheep.org Date: Sun, 9 May 2004 22:02:39 +0200 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 X-AntiVirus: checked by Vexira MailArmor (version: 2.0.1.16; VAE: 6.25.0.3; VDF: 6.25.0.55; host: postbode01.zonnet.nl) X-Spam-Score: 1.0 (+) X-Spam-Report: autolearn=no,FROM_ENDS_IN_NUMS=0.869,RCVD_IN_SORBS=0.1 Subject: LF: TX-ouput transformer problems Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.9 required=5.0 tests=FROM_ENDS_IN_NUMS autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 2 Hello all, I completed my G0MRF-transmitter, and today I've done the first tests on it. All is working fine, except the output circuit. As far as I can see now, the outputt-transformer on the FET's is not good. I'm using an old core from the HV-circuit of a computer monitor. I got this tip from Jim, M0BMU a while ago. Core size is about 63x39x14mm (2 "C"shaped halves, held together with a metal spring clip) I payed a lot off atention to have no air gap. Used 10 turns on the primary side, centre tapped. (That means 2 times 5 turns.......) Secundairy coil max. 21 turns with taps, all as described in the original design. Well, at 15V drain voltage I already had 9Amp........ With 40V over 50 Ohm....... FET's got hot........ I changed primairy to 2 times 7 turns instead of 2 times 5 turns, and that gave me 15V, 5Amp with also around 40V over 50 Ohm. So, higher efficiency...... I wonder if anyone has experience with these core's and have hints about number of turns to be used, before I start to get into endless rewinding coils etc. 73 Dick, pa4vhf