Return-Path: <owner-rsgb_lf_group@blacksheep.org> Received: (qmail 5568 invoked from network); 30 Apr 2003 08:21:06 -0000 Received: from marstons.services.quay.plus.net (212.159.14.223) by mailstore with SMTP; 30 Apr 2003 08:21:06 -0000 Received: (qmail 29661 invoked by uid 10001); 30 Apr 2003 08:21:06 -0000 X-MSMail-Priority: High Received: from post.thorcom.com (193.82.116.70) by marstons.services.quay.plus.net with SMTP; 30 Apr 2003 08:21:06 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.14) id 19Amp1-00041B-08 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 30 Apr 2003 09:20:11 +0100 Received: from [212.1.130.143] (helo=smtp-1.visp.telinco.net) by post.thorcom.com with esmtp (Exim 4.14) id 19Amov-000412-KI for rsgb_lf_group@blacksheep.org; Wed, 30 Apr 2003 09:20:05 +0100 Received: from [80.40.83.101] (helo=standalone) by smtp-1.visp.telinco.net with smtp (Exim 3.36 #1) id 19Amou-0006UI-00 for rsgb_lf_group@blacksheep.org; Wed, 30 Apr 2003 09:20:05 +0100 Received: by localhost with Microsoft MAPI; Wed, 30 Apr 2003 09:19:15 +0100 Message-ID: <01C30EF9.91BF8840.g4jnt@thersgb.net> From: "Andy talbot" <g4jnt@thersgb.net> To: rsgb_lf_group@blacksheep.org Date: Wed, 30 Apr 2003 09:15:36 +0100 Importance: high X-Priority: 1 X-Mailer: Microsoft Internet E-mail/MAPI - 8.0.0.4211 MIME-Version: 1.0 Subject: LF: RE: LF Tuning meter Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=2.0 required=5.0tests=X_PRIORITY_HIGHversion=2.53 X-Spam-Level: ** X-Spam-Checker-Version: SpamAssassin 2.53 (1.174.2.15-2003-03-30-exp) 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: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Hi Jim - Can I have a copy please - to the other account actalbot@dstl.gov.uk. If it uses the design I think is most likely - is it immune to even harmonic distortion products in the output waveform. (OK, there should never be any, but...) Andy G4JNT -----Original Message----- From: James Moritz [SMTP:j.r.moritz@herts.ac.uk] Sent: 2003/04/29 15:37 To: rsgb_lf_group@blacksheep.org Subject: LF: LF Tuning meter Dear LF Group, For tuning LF antennas, I have for some time been using an oscilloscope to monitor the current and voltage waveforms at the TX output. Resonance occurs when V and I are in phase, and the load resistance is 50ohms when V/I = 50. This is very easy to use provided a scope is to hand, but not very useful if it isn't. An SWR bridge can be used, but it only indicates the degree of mismatch, so tuning is still a matter of trial and error. So with a mind towards future /P operations, I have built a self-contained tuning meter. The prototype has 2 meters - one indicates phase, while the other can be switched between voltage and current to determine the load resistance. The circuit is slightly more complex than an SWR bridge, but not by very much - it uses 12 diodes, 3 toroid cores and a few other passive components. It does not require an external power supply, and is usable with TX power between about 20W and 1.8kW. I have written a 3 page article about it - it is a pdf file of about 190k, so too big for the reflector, but I can e-mail it as an attachment to those who are interested. If someone would like to put it on their web site, they would be more than welcome! Cheers, Jim Moritz 73 de M0BMU