Return-Path: Received: (qmail 12828 invoked from network); 1 Nov 2001 12:42:39 -0000 Received: from unknown (HELO murphys-inbound.services.quay.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 1 Nov 2001 12:42:39 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 28587 invoked from network); 1 Nov 2001 12:42:30 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys.services.quay.plus.net with SMTP; 1 Nov 2001 12:42:30 -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 15zH2J-0007Fe-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 01 Nov 2001 12:33:31 +0000 Received: from mailhost.netscapeonline.co.uk ([194.201.52.152]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 15zH2G-0007FV-00 for rsgb_lf_group@blacksheep.org; Thu, 01 Nov 2001 12:33:29 +0000 Received: from ldsas12-76-127-154.cw-visp.com ([212.137.127.154] helo=netscapeonline.co.uk) by mailhost.netscapeonline.co.uk with esmtp (Exim 3.02 #1) id 15zGsI-0005K4-00 for rsgb_lf_group@blacksheep.org; Thu, 01 Nov 2001 12:23:11 +0000 Message-ID: <3BE140EC.ED79750E@netscapeonline.co.uk> Date: Thu, 01 Nov 2001 12:32:44 +0000 From: "gii3kev" Organization: Netscape Online member X-Mailer: Mozilla 4.6 [en-gb]C-CCK-MCD NetscapeOnline.co.uk (Win95; I) X-Accept-Language: en-GB,en MIME-Version: 1.0 To: "rsgb rsgb" Subject: LF: best coil Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Shorted turns, turns left floating, coils within coils are not the way to proceed, althought this is a convenient method of resonating an antenna system. Having experimented with the above methods to obtain resonance, measure the inductance, then proceed to make a single layer coil that is exactly resonant at the desired frequency of operation. If it is found necessary to make a fine adjustment for a very precise frequency then use a small variable coil in series with the main coil at the cold end, and with a minimum of turns to achieve the object. If you have a vertical antenna around 100 feet plus the above exercise is not difficult, however with smaller vertical antennas where a lot of L is required obtaining resonance and especially fine tuning could be very critical, therefore one would possibly have to resort to the more lossy approach of having coils with shorted turns, variometers or shorted copper variable loops within the main inductor. One other approach is to use a suitable ferrite core material, that does not saturate, to fine tune, this is probably the most efficient method. The inductance required at my station to resonate the antenna is less than 450 microH so I do not have any real problems. With a little effort given time I could probably do away with the coil, by adding another couple of inv L's at 32 m high and over 100 m horiz. G3KEV