Return-Path: Received: (qmail 2996 invoked from network); 21 Jul 2004 12:46:21 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore01.plus.net with SMTP; 21 Jul 2004 12:46:21 -0000 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1BnGUa-0007oH-Cc for dave@picks.force9.co.uk; Wed, 21 Jul 2004 13:46:40 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1BnGUF-000EMG-0D for dave@picks.force9.co.uk; Wed, 21 Jul 2004 13:46:19 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1BnGTb-0000zZ-9o for rs_out_1@blacksheep.org; Wed, 21 Jul 2004 13:45:39 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1BnGTa-0000zQ-TL for rsgb_lf_group@blacksheep.org; Wed, 21 Jul 2004 13:45:38 +0100 Received: from cas-mta3-fe.casema.nl ([83.80.1.28] helo=mta.casema.nl) by relay.thorcom.net with esmtp (Exim 4.34) id 1BnGTS-0006Mr-Ov for rsgb_lf_group@blacksheep.org; Wed, 21 Jul 2004 13:45:38 +0100 Received: from pcprive (535582D3.cable.casema.nl [83.85.130.211]) by cas-mta3.mgmt.casema.nl (iPlanet Messaging Server 5.2 HotFix 1.21 (built Sep 8 2003)) with SMTP id <0I1700M6SCROH8@cas-mta3.mgmt.casema.nl> for rsgb_lf_group@blacksheep.org; Wed, 21 Jul 2004 14:45:24 +0200 (CEST) Date: Wed, 21 Jul 2004 14:45:24 +0200 From: haagrimbergen To: rsgb_lf_group@blacksheep.org Message-id: <001601c46f20$9801ade0$d3825553@pcprive> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V5.00.2615.200 X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-Priority: 3 X-MSMail-priority: Normal X-Spam-Score: 0.8 (/) X-Spam-Report: autolearn=no,HTML_30_40=0.809,HTML_MESSAGE=0.001 Subject: LF: Another kind of LF-PA? 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=0.8 required=5.0 tests=HTML_30_40,HTML_MESSAGE 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-Spam-Filtered: by PlusNet SpamCORE (v3.00) Content-transfer-encoding: 8bit

Dear OM's

I was pondering over using the horizontal TV-deflection system as a PA for LF. By stretching the flyback time to 50 percent of the period, using a push-pull stage with two identical circuits and then subtracting both outputs from each other should give a nearly perfect sine-output.

So I breadboarded a test circuit with two IRF730 FET's and after ample experiments it resulted in over 50 W RF on 136 kHz in a 50 ohm dummyload with 70 V dc input. Efficiency proved to be over 90 percent. Vdrain was abt 260 V peak and Isource of each FET was abt 2.2 A peak, both well within spec.

Measured with a spectrum-analyser: even harmonics were more than 40 dB and 3rd harmonic was 23 dB below fundamental.

Is this contraption already known yet as an LF-PA ??

If so, then:

1) What class of operation is it ?

2) I re-invented the wheel.

Thanks in advance for your comments

73 frm Harry, PA0LQ since 1946.