Return-Path: Received: (qmail 59722 invoked from network); 2 Mar 2005 21:00:51 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore01.plus.net with SMTP; 2 Mar 2005 21:00:51 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1D6azL-000HrL-TJ for dave@picks.force9.co.uk; Wed, 02 Mar 2005 21:02:38 +0000 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1D6azL-000Hr7-2N for dave@picks.force9.co.uk; Wed, 02 Mar 2005 21:02:35 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1D6azN-0003Ay-VH for dave@picks.force9.co.uk; Wed, 02 Mar 2005 21:02:38 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1D6ax7-0000tV-Hv for rs_out_1@blacksheep.org; Wed, 02 Mar 2005 21:00:17 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1D6ax1-0000oh-0h for rsgb_lf_group@blacksheep.org; Wed, 02 Mar 2005 21:00:11 +0000 Received: from mta208-rme.xtra.co.nz ([210.86.15.119]) by relay.thorcom.net with esmtp (Exim 4.43) id 1D6awy-0004XW-BZ for rsgb_lf_group@blacksheep.org; Wed, 02 Mar 2005 21:00:10 +0000 Received: from mta2-rme.xtra.co.nz ([210.86.15.240]) by mta208-rme.xtra.co.nz with ESMTP id <20050302205954.NLGF5260.mta208-rme.xtra.co.nz@mta2-rme.xtra.co.nz> for ; Thu, 3 Mar 2005 09:59:54 +1300 Received: from bob2l2u6k2n1g3 ([210.86.83.14]) by mta2-rme.xtra.co.nz with SMTP id <20050302205953.GFKP8463.mta2-rme.xtra.co.nz@bob2l2u6k2n1g3> for ; Thu, 3 Mar 2005 09:59:53 +1300 Message-ID: <000601c51f6a$c8687310$e901a8c0@bob2l2u6k2n1g3> From: "Vernall" To: rsgb_lf_group@blacksheep.org References: <6.1.0.6.2.20050301115700.03662eb0@mail.casema.nl> <004d01c51e98$ec121f00$c401a8c0@quaycustomer> Date: Thu, 3 Mar 2005 09:58:50 +1300 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-SPF-Result: relay.thorcom.net: domain of xtra.co.nz designates 210.86.15.119 as permitted sender X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=failed,none Subject: LF: Re: Re: Current "lost" in loading coil Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Hi all, The discussion has brought out some interesting points on what goes on in a practical loading coil. I would like to investigate (measure) some vector relationships of current and voltage on a practical setup, but in the meantime I am occupied with preparing for an LF DX weekend at Quartz Hill, so it will be a while till I can find time to do quantitative testing. I'm interested to find out if maximum current in to the "cold end" of the loading coil corresponds with maximum radiation (far field, not near field) from the system (system being not only the wire connected to the "hot end" of the loading coil). One can expect a big difference in relationships between tuned and untuned. When tuned (the usual situation for LF transmitting) one can expect an approximate linear voltage rise (similar volts per turn) and at the top "hot end" it will be some Q times the voltage applied at the "cold end". If there is similar stray capacitance per turn, then the current "lost" has an approximate linear distribution up the coil, as "lost current" is proportional to driving voltage, which increases along the coil. There will also be a phase shift due to physical length of wire in the inductor, with 360 degrees corresponding to a wavelength (even for applying DC, there is a finite time from applying excitation at one end till current comes out the other end, it is the "propagation delay" that forms the phase shift for steady state sinewave excitation). A coil winding length of 100 metres of wire is about 4.5% of a wavelength, or some 16 degrees for 136 kHz. The stray capacitance will of course modify the ideal situation of the 16 degrees being proportional to length along the winding, especially around the upper part of a resonant coil where the voltage is highest. 73, Bob ZL2CA