Return-Path: Received: from mtain-mg09.r1000.mx.aol.com (mtain-mg09.r1000.mx.aol.com [172.29.96.209]) by air-db04.mail.aol.com (v127_r1.1) with ESMTP id MAILINDB041-85f04b84517a263; Tue, 23 Feb 2010 17:06:51 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mg09.r1000.mx.aol.com (Internet Inbound) with ESMTP id 77123380000BF; Tue, 23 Feb 2010 17:06:49 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Nk2sT-0003kP-0q for rs_out_1@blacksheep.org; Tue, 23 Feb 2010 22:05:13 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Nk2sS-0003kG-Hf for rsgb_lf_group@blacksheep.org; Tue, 23 Feb 2010 22:05:12 +0000 Received: from mhost02h.leeds.ac.uk ([129.11.77.151]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Nk2sP-0007R2-U8 for rsgb_lf_group@blacksheep.org; Tue, 23 Feb 2010 22:05:12 +0000 Received: from APOLLO1.ds.leeds.ac.uk (apollo1.leeds.ac.uk [129.11.5.4]) by mhost02h.leeds.ac.uk (8.14.3/8.14.3) with ESMTP id o1NM5388002357 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NOT) for ; Tue, 23 Feb 2010 22:05:04 GMT Received: from HERMES8.ds.leeds.ac.uk ([fe80::39ce:23e:d0b5:7e24]) by APOLLO1.ds.leeds.ac.uk ([129.11.5.4]) with mapi; Tue, 23 Feb 2010 22:05:03 +0000 From: Chris Trayner To: "rsgb_lf_group@blacksheep.org" Date: Tue, 23 Feb 2010 22:05:01 +0000 Thread-Topic: LF: VLF_8.79 kHz Thread-Index: Acq01D/oXdS3eFilSL6w7VzXazIhpg== Message-ID: References: <27454582.2927283.1266931019627.JavaMail.fmail@mwmweb078> In-Reply-To: <27454582.2927283.1266931019627.JavaMail.fmail@mwmweb078> Accept-Language: en-US, en-GB Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, en-GB MIME-Version: 1.0 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: VLF_8.79 kHz Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=LINES_OF_YELLING, TO_ADDRESS_EQ_REAL 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-aol-global-disposition: G x-aol-sid: 3039ac1d60d14b8451791fc2 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) Dear All, John Rabson, F5VLF, is having trouble posting to this group. He asked me= to forward this for him, which he has sent unsuccessfully twice: --------------- Clank, The reflector has twice not delivered the attached. Would you try for me,= please? 73 John *********** BEGIN FORWARDED MESSAGE *********** On 23/02/2010 at 14:16 John RABSON wrote: From: John RABSON To: rsgb_lf_group@blacksheep.org Date: Tue, 23 Feb 2010 15:51:00 +0100=20 Subject: Re: LF: VLF_8.79 kHz My LF ground system consists of nine rods each 1 m long, separated by about 2 m. if I connect them in parallel the inductance at 980 Hz is about 7?H, and the resistance is about 25 ohms. This suggests that, at the frequencies we are considering, this is an essentially resistive termination and we don't need to cancel out the reactive part. =20 If we place a similar setup at the other end of a long wire we should see of the order of 50 ohms. Given that we are working at audio frequency, perhaps the step-up transformer from 8 ohms could use conventional soft iron laminations. At 50 Hz, my colleagues used to use a rule of thumb of 20VA per pound of laminations but I can't remember how this figure varied with frequency. Can any audio power engineers please comment? 73 John F5VLF ----------------------- Dr Chris Trayner School of Electronic & Electrical Engineering, The University of Leeds, Leeds LS2 9JT, United Kingdom Tel: +44 113 34 32053 Fax: +44 113 34 32032