Return-Path: Received: from rly-dg02.mx.aol.com (rly-dg02.mail.aol.com [172.19.151.86]) by air-dg05.mail.aol.com (v125.7) with ESMTP id MAILINDG052-5ac4b0d4ce145; Wed, 25 Nov 2009 10:27:51 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dg02.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDG027-5ac4b0d4ce145; Wed, 25 Nov 2009 10:27:31 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NDJlG-0003gX-JP for rs_out_1@blacksheep.org; Wed, 25 Nov 2009 15:26:30 +0000 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NDJlF-0003gA-JY for rsgb_lf_group@blacksheep.org; Wed, 25 Nov 2009 15:26:29 +0000 Received: from mailout05.t-online.de ([194.25.134.82]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NDJlB-0003pN-Ri for rsgb_lf_group@blacksheep.org; Wed, 25 Nov 2009 15:26:29 +0000 Received: from fwd09.aul.t-online.de by mailout05.t-online.de with smtp id 1NDJj2-0007Hu-03; Wed, 25 Nov 2009 16:24:12 +0100 Received: from df2py (XHKbO0Z6ohR9IGZkzAs5ZMdRlCtceZ-NozBjg2nN9WvlQVjOVyEAdh8US5Y0hVYwBk@[80.187.109.101]) by fwd09.t-online.de with esmtp id 1NDJit-1YhzQO0; Wed, 25 Nov 2009 16:24:03 +0100 From: "Wolf Ostwald" To: References: Date: Wed, 25 Nov 2009 16:25:39 +0100 Message-ID: MIME-Version: 1.0 X-Mailer: Microsoft Office Outlook 11 In-Reply-To: X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Thread-Index: AcpttRycc7MT6VpBRQOTEglJj2WnhQAKNOEg X-ID: XHKbO0Z6ohR9IGZkzAs5ZMdRlCtceZ-NozBjg2nN9WvlQVjOVyEAdh8US5Y0hVYwBk X-TOI-MSGID: c89e806d-5c12-4ba2-a136-ad8da1c306ff X-Spam-Score: 2.6 (++) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RCVD_IN_BL_SPAMCOP_NET=1.332,RCVD_IN_SORBS_WEB=1.236,UNPARSEABLE_RELAY=0.001 Subject: LF: instability on MosFet amps Content-Type: multipart/alternative; boundary="----=_NextPart_000_0036_01CA6DEB.F41F13E0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.3 required=5.0 tests=HTML_50_60, HTML_FONTCOLOR_UNKNOWN,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-AOL-IP: 193.82.116.20 ------=_NextPart_000_0036_01CA6DEB.F41F13E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hello group ! I found that almost all amp configurations generate harmonics. In case of a homebrewed HF amp, with a push -pull design, I had to build hi-pass filters with a resistive termination, so called split filters, for each band. Without dissipating the harmonic energy the stage will have to cope with excess voltages and thus bury the MosFets . My last amp stage for the DI2BJ-beacon is followed by a hi-pass that opens at 750 kcs . This way the first harmonic and all the higher ones go into thermal dissipation. A T-type adjustable low-pass is used to match and reduce harmonics further. Have fun de wolf df2py ------=_NextPart_000_0036_01CA6DEB.F41F13E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hel= lo group !

I= found that almost all amp configurations generate harmonics. In case of a homebrewed HF amp,= with a push –pull design, I had to build hi-pass filters with a resistive te= rmination, so called split filters, for each band. Without dissipating the harmon= ic energy the stage will have to cope with excess voltages and thus bury the Mos= Fets .

My= last amp stage for the DI2BJ-beacon is followed by a hi-pass that opens at 750 kcs . This way= the first harmonic and all the higher ones go into thermal dissipation.

A= T-type adjustable low-pass is used to match and reduce harmonics further.

Hav= e fun &nbs= p; de wolf df2py

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