Return-Path: Received: (qmail 9312 invoked from network); 30 Oct 2001 21:20:22 -0000 Received: from unknown (HELO warrior.services.quay.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 30 Oct 2001 21:20:22 -0000 Received: (qmail 792 invoked from network); 30 Oct 2001 21:17:55 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior.services.quay.plus.net with SMTP; 30 Oct 2001 21:17:55 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 15ygBf-0002pH-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 30 Oct 2001 21:12:43 +0000 Received: from chalfont.mail.uk.easynet.net ([212.135.1.67]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 15ygBd-0002pB-00 for rsgb_lf_group@blacksheep.org; Tue, 30 Oct 2001 21:12:41 +0000 Received: from ericadodd (tnt-6-73.easynet.co.uk [195.40.201.73]) by chalfont.mail.uk.easynet.net (Postfix) with SMTP id AFE691D56B9 for ; Tue, 30 Oct 2001 21:11:58 +0000 (GMT) Message-ID: <000a01c16187$aec96d00$49c928c3@ericadodd> From: "g3ldo" To: rsgb_lf_group@blacksheep.org Subject: LF: Multi-layer loading coils Date: Tue, 30 Oct 2001 21:12:19 -0000 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 5.50.4522.1200 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: Some time ago I obtained a Decca loading coil on one of my visits to the Crawley radio club. The Decca coil on page 64 of the LF Handbook illustrates the general construction of one of these coils and the Decca loading and matching system is shown on page 13. The Decca system used five transmitters multiplexed (if this is the right word) into a single transmitting antenna so the coils are quite complex, comprising several separate windings wound using a low capacity basket weave on the same former. The purpose of this exercise was to see if this coil might be suitable for amateur LF. For the coil to be of any use it would have to be completely rebuilt. There seems to be two different types of construction. The one shown on page 84 of the LF book is an older type, which uses Perspex formers and are fixed in place using an adhesive. This means that it is very difficult to dismantle without damage. Furthermore the Litz wire is difficult solder - you have to use methods as described on Page 84. The later coils use a former ribs made of plastic using a sort of Lego construction, which is held in place by the wire itself. Furthermore, the Litz can be soldered by just dipping the end into a solder pot (after first removing the plastic outer insulation). The coil was easily dismantled in an afternoon and a finisher up with a large plastic box of Lego bits, about 25kg of Litz and a basic coil former comprising a hard plastic cylinder 449mm in diameter and 220mm long. As you can see from the photo, the coil will have to be multi-layered. Is there any performance penalty in using such a method of construction compared with using the straight single layered coil?. One problem that occurs to me is the potential gradient across the coil but I know how to avoid any difficulties in this regard. I wish to thank Dick, Rick and Andy for multi-layer coil formula. At the moment I think that empirical experimenting is going to be the only way of obtaining any useful information. Has anyone else got a Decca coil and have they tried using it? Regards, Peter, G3LDO e-mail Web