Return-Path: Received: (qmail 11651 invoked from network); 2 May 2003 15:54:59 -0000 Received: from netmail01.services.quay.plus.net (212.159.14.219) by mailstore with SMTP; 2 May 2003 15:54:59 -0000 Received: (qmail 23267 invoked by uid 10001); 2 May 2003 15:54:59 -0000 Received: from post.thorcom.com (193.82.116.70) by netmail01.services.quay.plus.net with SMTP; 2 May 2003 15:54:59 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.14) id 19Bcra-0003nr-8c for rsgb_lf_group-outgoing@blacksheep.org; Fri, 02 May 2003 16:54:18 +0100 Received: from [206.173.118.93] (helo=uhura.concentric.net) by post.thorcom.com with esmtp (Exim 4.14) id 19BcrU-0003ni-Rr for rsgb_lf_group@blacksheep.org; Fri, 02 May 2003 16:54:13 +0100 Received: from marconi.concentric.net (marconi.concentric.net [206.173.118.71]) by uhura.concentric.net [Concentric SMTP Routing 1.0] id h42FsAs23377 for ; Fri, 2 May 2003 11:54:11 -0400 (EDT) Received: from jka ([208.37.242.34]) by marconi.concentric.net (8.9.1a+patch04072003) id LAA11520; Fri, 2 May 2003 11:54:09 -0400 (EDT) Message-ID: <002801c310c3$4e27bc80$09dc9384@jka> From: "John Andrews" To: rsgb_lf_group@blacksheep.org References: <5.1.0.14.0.20030430120518.00ade070@gemini.herts.ac.uk> <001501c31001$6a079780$bee5fc3e@l8p8y6> <5.1.0.14.0.20030502115241.025564e8@gemini.herts.ac.uk> Date: Fri, 2 May 2003 11:55:49 -0400 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: Re: LF: Mains Cable and other transmission lines Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-6.6 required=5.0tests=REFERENCESversion=2.53 X-Spam-Checker-Version: SpamAssassin 2.53 (1.174.2.15-2003-03-30-exp) X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Jim, et al: With the proposed 100 watt transmitter output limit here in the U.S., we can be a little more conservative with audio amplifiers used as transmitter PA's. I have been playing with a nominal "8 ohm" amplifier (actually two "4 ohm" amps in bridging configuration), and using a 1:2 transformer that presents 12.5 ohms to the PA when terminated in 50 ohms. As noted in the LF Handbook, the output impedance of these amps can rise with frequency, and there is plenty of power available with the 100 watt restriction. John Andrews, W1TAG