Return-Path: Received: (qmail 10391 invoked from network); 29 Oct 2001 15:26:06 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO murphys-inbound.services.quay.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 29 Oct 2001 15:26:06 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 18396 invoked from network); 29 Oct 2001 15:23:34 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys.services.quay.plus.net with SMTP; 29 Oct 2001 15:23:34 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 15yE8o-0007YN-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 29 Oct 2001 15:15:54 +0000 Received: from mail.cc.kuleuven.ac.be ([134.58.10.6]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 15yE8n-0007YI-00 for rsgb_lf_group@blacksheep.org; Mon, 29 Oct 2001 15:15:53 +0000 Received: from LCBD15.fys.kuleuven.ac.be (LCBD15.fys.kuleuven.ac.be [134.58.80.15]) by mail.cc.kuleuven.ac.be (8.9.3/8.9.0) with SMTP id QAA867086 for ; Mon, 29 Oct 2001 16:15:10 +0100 Message-ID: <3.0.1.16.20011029161314.30eff79c@mail.cc.kuleuven.ac.be> X-Sender: pb623250@mail.cc.kuleuven.ac.be X-Mailer: Windows Eudora Pro Version 3.0.1 (16) Date: Mon, 29 Oct 2001 16:13:14 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" Subject: Re: LF: Decca Coils In-reply-to: <001501c16079$afd27840$3aca28c3@ericadodd> References: <2614258.1004295195891.JavaMail.computernetworks@gomailjtp05> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hello Peter, I got 2 formulae from 'Grundlagen der Hochfrequenztechnik' : 1. For 'slim' coils (H>>D) : L = 2*Pi*N^2*D(3.47/(1+2.2*H/D)-K*C/H) where L = inductance (nH) N = windings D = average coil diameter (cm) H = coil length (cm) C = thickness of the wirelayers (all together, in cm) K = correction factor depending on H/C ratio : L/C K 2 0.10 3 0.15 5 0.23 10 0.27 15 0.30 20 0.31 30 0.32 2. For 'fat' coils (H<=D) : L = 78*L^2*D/(3*D+9*H+10*C) If the coil is not close wound then a correction factor dL has to be taken into account : dL = 2*Pi*D*(ln(b/d)+0.155) where b = wire spacing (centre wire to centre wire) d = wire diameter ln = natural logaritm dL has to be added to L (but since always b > d , dL will be negative). I hope the above gives at least an idea where to start with, 73, Rik ON7YD >I am dismantling a Decca loading coil with the objective of rebuilding it to >load my 16m high antenna. It will be converted so that it is a multi-layer >coil. Does anyone know of a formula for multilayer coils where the spacing >between the layers is several times the wire diameter? > >Regards, >Peter, G3LDO > >e-mail > >Web > > > >