Return-Path: Received: (qmail 31147 invoked from network); 12 May 2004 08:38:34 -0000 Received: from unknown (HELO ptb-mxscan02.plus.net) (212.159.14.236) by ptb-mailstore02.plus.net with SMTP; 12 May 2004 08:38:34 -0000 Received: (qmail 21704 invoked from network); 12 May 2004 08:38:33 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 Received: from ptb-mxcore02.plus.net (212.159.14.216) by ptb-mxscan02.plus.net with SMTP; 12 May 2004 08:38:32 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1BNpG4-0005Fg-CF for dave@picks.force9.co.uk; Wed, 12 May 2004 08:38:32 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1BNpF5-0008Gk-UD for rs_out_1@blacksheep.org; Wed, 12 May 2004 09:37:31 +0100 Received: from [213.232.95.59] (helo=relay.salmark.net) by post.thorcom.com with esmtp (Exim 4.14) id 1BNpF5-0008Gb-9s for rsgb_lf_group@blacksheep.org; Wed, 12 May 2004 09:37:31 +0100 Received: from imo-d03.mx.aol.com ([205.188.157.35]) by relay.salmark.net with esmtp (Exim 4.24) id 1BNvnU-0003qq-6Q for rsgb_lf_group@blacksheep.org; Wed, 12 May 2004 16:37:28 +0100 X-Fake-Domain: G0MRF@aol.com Received: from G0MRF@aol.com by imo-d03.mx.aol.com (mail_out_v37_r1.3.) id l.8d.aa59ac4 (3980) for ; Wed, 12 May 2004 04:37:15 -0400 (EDT) From: G0MRF@aol.com Message-ID: <8d.aa59ac4.2dd33c3a@aol.com> Date: Wed, 12 May 2004 04:37:14 EDT To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: 8.0 for Windows sub 670 X-Spam-Score: 0.7 (/) X-Spam-Report: autolearn=no,HTML_MESSAGE=0.001,HTML_TAG_BALANCE_HTML=0.411,NO_REAL_NAME=0.285 Subject: LF: Output transformer problems Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_MESSAGE, HTML_TAG_BALANCE_HTML,NO_REAL_NAME 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: 1 Content-transfer-encoding: 8bit In a message dated 5/11/04 10:59:45 PM GMT Daylight Time, vernall@xtra.co.nz writes:

>well I rewound the ouput transformer.
>Again I have problems, and when checking the signal on
>a spectrum analyzer I found that it is peaking on the second harmonic.
>So it transmits the main signal on 272kHz.........
>136kHz is also present at the ouput, but much much weaker.
>
>It really makes me puzzling.

Double trouble. Are you certain of the windings being correctly phased for
"push-pull"? You may have made a "push-push doubler"???

73, Bob

Hi.

Have been following this topic. Maybe this will help.

I've just wound 10 turns on a 58mm 3C90 core and the inductance measured 353uH.

The 10nF on the drains are intended for spike suppression not resonance.

If you can change the design to get class E, at your required output power, then efficiency / dissipation / drain transients would all improve.

The square wave drive should not contain significant amounts of second harmonic. The "push pull doubler" can be created by a fault in the FETs insulating washers, or if they are directly connected to a common isolated heatsink.

Do you have square waves on the drive? Upside down Schottky diodes will distort the drive and cause excess dissipation as the FETs will not be fully 'on'

Good luck

David G0MRF