Return-Path: Received: (qmail 29681 invoked from network); 30 Mar 2002 20:52:16 -0000 Received: from unknown (HELO murphys-inbound.services.quay.plus.net) (212.159.14.225) by exhibition.plus.net with SMTP; 30 Mar 2002 20:52:16 -0000 Received: (qmail 14485 invoked from network); 30 Mar 2002 20:51:59 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys.services.quay.plus.net with SMTP; 30 Mar 2002 20:51:59 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 16rRGw-0004lO-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 30 Mar 2002 22:24:30 +0000 Received: from mta1-rme.xtra.co.nz ([210.86.15.129]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 16rRGu-0004lD-00 for rsgb_lf_group@blacksheep.org; Sat, 30 Mar 2002 22:24:28 +0000 Received: from xtr743187 ([202.27.178.179]) by mta1-rme.xtra.co.nz with SMTP id <20020330204553.ONHY8792.mta1-rme.xtra.co.nz@xtr743187> for ; Sun, 31 Mar 2002 08:45:53 +1200 Message-ID: <001501c1d82c$0bdedc80$b3b21bca@xtr743187> From: "Vernall" To: rsgb_lf_group@blacksheep.org References: Subject: LF: Re: RE: loop inductance Date: Sun, 31 Mar 2002 08:46:15 +1200 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2919.6600 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hi all, I've not been following all bulletins on loops, but a comment on frequency range should be made for any "inductance formula". Because of "long" wavelengths at LF, most amateur loops are "small" in terms of wavelengths, so a "constant current" approximation can usually be made. When the loop diameter is a significant part of a wavelength, the current distribution starts to have "standing waves" and the radiation characteristics (impedance and pattern) are quite different to the electrically small loop. For a multi-turn loop, inter-turn capacitance also modifies the "inductance" at higher frequencies, so there comes a time when a single turn loop (possibly with parallel wires) is the better performer. I'm not sure where the regions are that low frequency inductance formulae need correction, and similarly for multi-turns. 73, Bob ZL2CA