Return-Path: Received: from rly-yc01.mail.aol.com (rly-yc01.mail.aol.com [172.18.205.144]) by air-yc04.mail.aol.com (v119.9) with ESMTP id MAILINYC43-1b646fbf42ca1; Thu, 27 Sep 2007 14:19:55 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-yc01.mail.aol.com (v119.9) with ESMTP id MAILRELAYINYC18-1b646fbf42ca1; Thu, 27 Sep 2007 14:19:36 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1IaxwB-0002UO-BR for rs_out_1@blacksheep.org; Thu, 27 Sep 2007 19:18:11 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1IaxwA-0002UF-U6 for rsgb_lf_group@blacksheep.org; Thu, 27 Sep 2007 19:18:10 +0100 Received: from mtaout03-winn.ispmail.ntl.com ([81.103.221.49]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Iaxw6-0007cU-Mv for rsgb_lf_group@blacksheep.org; Thu, 27 Sep 2007 19:18:10 +0100 Received: from aamtaout03-winn.ispmail.ntl.com ([81.103.221.35]) by mtaout03-winn.ispmail.ntl.com with ESMTP id <20070927181736.PGGH13.mtaout03-winn.ispmail.ntl.com@aamtaout03-winn.ispmail.ntl.com> for ; Thu, 27 Sep 2007 19:17:36 +0100 Received: from enigma ([82.26.228.131]) by aamtaout03-winn.ispmail.ntl.com with SMTP id <20070927181736.XEKQ26699.aamtaout03-winn.ispmail.ntl.com@enigma> for ; Thu, 27 Sep 2007 19:17:36 +0100 Message-ID: <000a01c80132$aae29df0$83e41a52@enigma> From: "Malcolm Harman" To: Date: Thu, 27 Sep 2007 19:17:28 +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,HTML_MESSAGE=0.001 Subject: LF: A question of calibration Content-Type: multipart/alternative; boundary="----=_NextPart_000_0007_01C8013B.0B43CC70" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.7 required=5.0 tests=FROM_ENDS_IN_NUMS,HTML_30_40, HTML_MESSAGE 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 : ------=_NextPart_000_0007_01C8013B.0B43CC70 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi. Can anyone reassure me. I am in the process of using PA0SE's most helpful article http://www.veron.n= l/tech/lf/fsm/pa0se.htm to assist in calibrating my 'Eton E5' as a field str= ength receiver for 500 kHz . He says: "Most field strength meters do not measure the electric but the ma= gnetic component of the electromagnetic field. But this is no problem becaus= e in the far field of the antenna (where we measure) there is a fixed relati= on between the electric and the magnetic field components: E/H=3D120*pi ohm= =3D377 ohm"=20 Then in the final paragraph of the 'Calibration' section he uses this same e= quation to convert A/m to V/m in a near field.=20 Not that I would want to question an expert, but I guess the far field issue= is something to do with the distance it takes for a plain wave to form from= an antenna and presumably the equation remains valid, even between the "Hel= mholtz coils" with the 377ohm relationship still applicable? 73 Malcolm (G3NZP, near Gatwick) ------=_NextPart_000_0007_01C8013B.0B43CC70 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Hi. Can anyone reassure me.

I am in the process of using PA0SE's mos= t=20 helpful article http://www.veron.nl/tech/lf/fsm/pa0se.htm<= /FONT> to assist in calibrating my= 'Eton E5' as a field=20 strength receiver for 500 kHz .

He says: "Most field strength= =20 meters do not measure the electric but the magnetic component of the=20 electromagnetic field. But this is no problem because in the far fie= ld=20 of the antenna (where we measure) there is a fixed= =20 relation between the electric and the magnetic field components: E/H=3D120*p= i=20 ohm=3D377 ohm"

Then in the final paragraph of the 'Calibr= ation'=20 section he uses this same equation to convert A/m to V/m i= n a=20 near field.

Not that I would want to question an exper= t, but=20 I guess the far field issue is something to do with the distance it takes fo= r a=20 plain wave to form from an antenna and presumably the equation remains=20 valid, even between the "Helmholtz coils" with the 377ohm=20 relationship still applicable?

73 Malcolm (G3NZP, near=20 Gatwick)

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