Return-Path: Received: (qmail 67107 invoked from network); 15 Feb 2005 19:02:06 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore01.plus.net with SMTP; 15 Feb 2005 19:02:06 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1D17xg-000OcK-HY for dave@picks.force9.co.uk; Tue, 15 Feb 2005 19:02:18 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1D17xe-000ObD-8R for dave@picks.force9.co.uk; Tue, 15 Feb 2005 19:02:14 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim) id 1D17ys-0008T3-32 for dave@picks.force9.co.uk; Tue, 15 Feb 2005 19:03:30 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1D17xC-0000oc-7D for rs_out_1@blacksheep.org; Tue, 15 Feb 2005 19:01:46 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1D17xB-0000oT-Rk for rsgb_lf_group@blacksheep.org; Tue, 15 Feb 2005 19:01:45 +0000 Received: from imo-m19.mx.aol.com ([64.12.137.11]) by relay.thorcom.net with esmtp (Exim 4.43) id 1D17x8-0004SP-BG for rsgb_lf_group@blacksheep.org; Tue, 15 Feb 2005 19:01:45 +0000 Received: from MarkusVester@aol.com by imo-m19.mx.aol.com (mail_out_v37_r3.8.) id l.29.6cee73e7 (2519) for ; Tue, 15 Feb 2005 14:01:33 -0500 (EST) From: MarkusVester@aol.com Message-ID: <29.6cee73e7.2f43a10d@aol.com> Date: Tue, 15 Feb 2005 14:01:33 EST To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: 8.0 for Windows sub 6104 X-SPF-Result: relay.thorcom.net: domain of aol.com designates 64.12.137.11 as permitted sender X-Spam-Score: 0.5 (/) X-Spam-Report: autolearn=no,HTML_10_20=0.295,HTML_MESSAGE=0.001,NO_REAL_NAME=0.178 Subject: LF: Re: Wilkinson combiner, Phase Shift 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-Spam-Filtered: by PlusNet SpamCORE (v3.00) Content-transfer-encoding: 8bit Dear LF Group,

one thing worth considering is the phase shift between the transistors and the antenna input, including all filters and matching circuitry. I have always tried to keep that at 0° or 180°, as this lets the FET's see a series resonant load. This becomes a high impedance in case of antenna detuning or arcing, a safe condition for a class-D voltage source. Actually I have not lost a single FET in spite of several antenna faults (... knocking on wood as I write this ;-).

Feeding a tap on the loading coil will introduce a phase shift close to 90°, showing impedance inversion. A Wilkinson combiner also adds in a quarterwave. But of course it is the total electrical length of the output chain at 137kHz that counts.

73
Markus, DF6NM