Return-Path: Received: (qmail 17477 invoked from network); 8 Jul 2003 12:53:28 -0000 Received: from netmail01.services.quay.plus.net (212.159.14.219) by mailstore with SMTP; 8 Jul 2003 12:53:28 -0000 Received: (qmail 9723 invoked by uid 10001); 8 Jul 2003 12:53:28 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from post.thorcom.com (193.82.116.70) by netmail01.services.quay.plus.net with SMTP; 8 Jul 2003 12:53:28 -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 19ZrxB-0007hD-Ny for rsgb_lf_group-outgoing@blacksheep.org; Tue, 08 Jul 2003 13:52:17 +0100 Received: from [213.218.75.233] (helo=smtp04.freeler.nl) by post.thorcom.com with esmtp (Exim 4.14) id 19Zrx7-0007h2-5L for rsgb_lf_group@blacksheep.org; Tue, 08 Jul 2003 13:52:13 +0100 Received: (qmail 23790 invoked from network); 8 Jul 2003 12:51:41 -0000 Received: from unknown (HELO w8k3f0.freeler.nl) ([62.21.137.217]) (envelope-sender ) by smtp04.freeler.nl (qmail-ldap-1.03) with SMTP for ; 8 Jul 2003 12:51:41 -0000 Message-ID: <5.1.0.14.0.20030708144529.009ecec0@POP3.freeler.nl> X-Sender: FRE0000086604@POP3.freeler.nl X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Tue, 08 Jul 2003 14:54:46 +0200 To: rsgb_lf_group@blacksheep.org From: "Dick Rollema" In-reply-to: <5.1.0.14.0.20030707113252.025bf530@gemini.herts.ac.uk> References: <000001c343db$8cb86760$5967fea9@p4o2b7> MIME-Version: 1.0 Subject: Re: LF: Field strength calcs. Content-Type: text/html; charset=windows-1252 X-Spam-Status: No, hits=-0.5 required=5.0tests=EMAIL_ATTRIBUTION,HTML_10_20,HTML_MESSAGE,IN_REP_TO, REFERENCES,REPLY_WITH_QUOTESversion=2.55 X-Spam-Checker-Version: SpamAssassin 2.55 (1.174.2.19-2003-05-19-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 Content-transfer-encoding: 8bit To All from PA0SE

Jim, M0BMU wrote:

The voltage induced in a loop is:

V = 2.1x10^-8 (fNAE)

where f = frequency (Hz)
        N = number of turns
        A = area (m^2)
        E = field strength (V/m)

Always assuming that the antennas are far enough apart for the loop to be in the "far field" (>1 - 2km seems to be enough)

I think 2km is not quite enough at 73kHz. I calculated the total field over perfect ground at 2km distance by means of a antenna simulation program. I found E/H = 342 ohm. In the far field E/H ought to be 377 ohm (= 120.pi ohm). So apparently at 2km the near field is not yet small enough to be negligible.

I found that even at 137kHz measurements were inconsistent at 2km so I changed to over 4km.

73, Dick, PA0SE