Return-Path: Received: from rly-me04.mx.aol.com (rly-me04.mail.aol.com [172.20.83.38]) by air-me06.mail.aol.com (v119.11) with ESMTP id MAILINME064-9b046fcc349127; Fri, 28 Sep 2007 05:03:26 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-me04.mx.aol.com (v119.11) with ESMTP id MAILRELAYINME044-9b046fcc349127; Fri, 28 Sep 2007 05:03:07 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1IbBk0-0000w9-CQ for rs_out_1@blacksheep.org; Fri, 28 Sep 2007 10:02:32 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1IbBjz-0000w0-WF for rsgb_lf_group@blacksheep.org; Fri, 28 Sep 2007 10:02:32 +0100 Received: from mtaout02-winn.ispmail.ntl.com ([81.103.221.48]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1IbBjv-0000S7-PU for rsgb_lf_group@blacksheep.org; Fri, 28 Sep 2007 10:02:31 +0100 Received: from aamtaout02-winn.ispmail.ntl.com ([81.103.221.35]) by mtaout02-winn.ispmail.ntl.com with ESMTP id <20070928090201.DCXH4.mtaout02-winn.ispmail.ntl.com@aamtaout02-winn.ispmail.ntl.com> for ; Fri, 28 Sep 2007 10:02:01 +0100 Received: from enigma ([82.26.238.15]) by aamtaout02-winn.ispmail.ntl.com with SMTP id <20070928090201.LZKG17393.aamtaout02-winn.ispmail.ntl.com@enigma> for ; Fri, 28 Sep 2007 10:02:01 +0100 Message-ID: <000601c801ae$38cc27a0$0fee1a52@enigma> From: "Malcolm Harman" To: References: <000a01c80132$aae29df0$83e41a52@enigma> <46FC071D.2090202@w1tag.com> Date: Fri, 28 Sep 2007 10:01:54 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Karma: 0: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: A question of calibration Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=FROM_ENDS_IN_NUMS 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 X-AOL-SCOLL-AUTHENTICATION: listenair ; SPF_helo : X-AOL-SCOLL-AUTHENTICATION: listenair ; SPF_822_from : John. Fascinating stuff and all your are papers duly saved. I sort of knew PA0SE must be right and while E/H = 377 ohms between the Helmholtz coils, we have to go to the far field of an antenna before a "plane" wave is sufficiently well formed and once again E/H = 377 ohms. Thanks for the clarification. 73 Malcolm. ----- Original Message ----- From: "John Andrews" To: Sent: Thursday, September 27, 2007 8:40 PM Subject: Re: LF: A question of calibration > Malcolm, > >> Hi. Can anyone reassure me. > > Be reassured. Your meter is measuring the magnetic field, and the > calibration setup is primarily generating a magnetic field. The cal is > being done under near-field conditions to permit the use of low power and > take advantage of knowing the mag field accurately based on geometry and > current measurement. The scale conversion to electric field remains valid > as long as you agree to take your real measurements under far-field > conditions. > > A further discussion of calibration techniques including a simpler > arrangement than Helmholtz coils may be found at: > http://www.w1tag.com/LF_FSM.htm > > John Andrews, W1TAG > >