Return-Path: Received: (qmail 19213 invoked from network); 17 Feb 2005 18:04:26 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore02.plus.net with SMTP; 17 Feb 2005 18:04:26 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1D1q1B-000FXa-Ec for dave@picks.force9.co.uk; Thu, 17 Feb 2005 18:04:52 +0000 Received: from [192.168.67.2] (helo=ptb-mxcore02.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1D1q18-000FVq-PU for dave@picks.force9.co.uk; Thu, 17 Feb 2005 18:04:47 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1D1q0c-000OlF-6m for dave@picks.force9.co.uk; Thu, 17 Feb 2005 18:04:14 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1D1pyC-00071B-I3 for rs_out_1@blacksheep.org; Thu, 17 Feb 2005 18:01:44 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1D1pyC-000712-6A for rsgb_lf_group@blacksheep.org; Thu, 17 Feb 2005 18:01:44 +0000 Received: from mailfe02.swip.net ([212.247.154.33] helo=swip.net) by relay.thorcom.net with esmtp (Exim 4.43) id 1D1py8-000207-RW for rsgb_lf_group@blacksheep.org; Thu, 17 Feb 2005 18:01:44 +0000 X-T2-Posting-ID: 3bgU4LVfFOB/SKpu7D1OzA== Received: from [212.151.19.99] ([212.151.19.99] verified) by mailfe02.swip.net (CommuniGate Pro SMTP 4.2.9) with ESMTP id 301263859 for rsgb_lf_group@blacksheep.org; Thu, 17 Feb 2005 19:01:25 +0100 Received: from 127.0.0.1 (AVG SMTP 7.0.300 [265.8.8]); Thu, 17 Feb 2005 18:02:01 -0100 Message-ID: <4214EA0B.4000505@tele2.se> Date: Thu, 17 Feb 2005 18:01:31 -0100 From: Johan Bodin User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206) X-Accept-Language: sv, en-us, en To: rsgb_lf_group@blacksheep.org References: In-Reply-To: Mime-Version: 1.0 X-SPF-Result: relay.thorcom.net: 212.247.154.33 is neither permitted nor denied by domain of tele2.se X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=failed,none Subject: Re: LF: RE: Matching Ropex Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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) Hi Dave, > The puzzle is why the Ropex has problems with a 50 ohm match at 136kHz if > the coil is grounded? The match is the same on an SWR bridge whether the pi > cct is in circuit or not. The Ropex protection cct seems to be some kind of > overcurrent detector in the 50ohm output but I can't remember which side of > the internal LPF it is placed. Hmmm... Maybe the Ropex protection circuit is TOO fast. 50 ohms is 50 ohms for a steady state signal, true, but I think the circuit trips on the key-down transient. With "hard keying" the inrush current into the antenna can be quite high due to the high Q. An antenna with a Q of 50, or so, is a very heavy "flywheel"! With 150W of feedline power, 5..10 kW (!) of reactive power will be circulating in the antenna... It takes quite a big kick to "spin it up" so to speak. 73 Johan SM6LKM -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.8.8 - Release Date: 2005-02-14