Return-Path: X-Spam-DCC: paranoid 1233; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.5 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,RATWARE_GECKO_BUILD,SPF_PASS autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u1TMURdK007395 for ; Mon, 29 Feb 2016 23:30:27 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aaWGL-00017f-Eq for rs_out_1@blacksheep.org; Mon, 29 Feb 2016 22:25:57 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aaWGL-00017W-1T for rsgb_lf_group@blacksheep.org; Mon, 29 Feb 2016 22:25:57 +0000 Received: from brian.netcom.co.uk ([217.72.171.64]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1aaWGJ-0005Fi-Hp for rsgb_lf_group@blacksheep.org; Mon, 29 Feb 2016 22:25:55 +0000 Received: from sb.abelian.org (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by brian.netcom.co.uk (Postfix) with ESMTP id 8D51A32008C for ; Mon, 29 Feb 2016 22:03:23 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by sb.abelian.org (Postfix) with ESMTP id C26BE28A0148 for ; Mon, 29 Feb 2016 22:25:54 +0000 (UTC) Message-ID: <56D4C572.5040400@abelian.org> Date: Mon, 29 Feb 2016 22:25:54 +0000 From: Paul Nicholson User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <56D08BEF.7070708@abelian.org> <8D33ED4DA8562EE-14E0-601004@webmail-vm018.sysops.aol.com> <56D0934B.1040700@abelian.org> <56D098D3.80501@abelian.org> <56D0B22B.2020107@abelian.org> <56D0B58A.80908@tiscali.co.uk> <56D0C373.1090004@abelian.org> <56D0CC55.1060400@tele2.se> <56D0D587.7080309@abelian.org> <56D1DEAF.10202@abelian.org> <56D1FD5F.3010301@abelian.org> <56D2DA6D.20209@tele2.se> <56D326F1.1000102@abelian.org> <56D33297.9080209@abelian.org> <56D37529.9070607@abelian.org> <6732A7AB5E094156B6AE3A33E58A964F@White> <56D3875A.4060405@abelian.org> <4F4F6D69C89949808409DA43533DE43D@Clemens0811> In-Reply-To: <4F4F6D69C89949808409DA43533DE43D@Clemens0811> X-Scan-Signature: 739d4fb39bd02fc5a2de5437a39bb056 Subject: Re: LF: MF: EbNaut Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.11 Status: O X-Status: X-Keywords: X-UID: 7137 Clemens wrote: > I would recommend feeding DC not via the center tap ... > ... Instead I would feed DC via two separate DC chokes. I understand. I've seen that arrangement in circuits of HF PAs and wondered why it was done that way. It would simplify the primary winding too. Thanks for the tip, I will certainly do that, I've got a couple of suitable chokes pulled from PC power supplies. I don't know why the transformer is running so much cooler after removing the AC grounding of the primary center. I don't think there was enough energy in those transients to account for the heat. Well, I'm learning quite a lot here and have a working PA and a coherent BPSK signal on-air, so I'm very pleased and appreciate all the advice. Another question for PA experts. In MOSFET power supplies for Tesla coils, it is standard practice to block the body diode of the FET using a Schottky diode in series with the drain and use an external fast recovery diode to carry any freewheeling current. This is because the body diodes have a terribly slow reverse recovery. I was wondering if this same reasoning carries over to LF/MF PA design, which covers similar frequency range. The power levels in TCs tend to be a lot higher though, perhaps that's the difference. -- Paul Nicholson --