Return-Path: Received: from mtain-db01.r1000.mx.aol.com (mtain-db01.r1000.mx.aol.com [172.29.64.85]) by air-me09.mail.aol.com (v127_r1.1) with ESMTP id MAILINME092-8bc14bab1ecfbc; Thu, 25 Mar 2010 04:29:03 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-db01.r1000.mx.aol.com (Internet Inbound) with ESMTP id C6E6E3800008C; Thu, 25 Mar 2010 04:29:01 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NuiQ3-0008As-8e for rs_out_1@blacksheep.org; Thu, 25 Mar 2010 08:27:59 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NuiQ2-0008Aj-Ta for rsgb_lf_group@blacksheep.org; Thu, 25 Mar 2010 08:27:58 +0000 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NuiQ0-0004eo-9C for rsgb_lf_group@blacksheep.org; Thu, 25 Mar 2010 08:27:58 +0000 Received: from abelian.netcom.co.uk (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by parrot.netcom.co.uk (Postfix) with ESMTP id 22E04328C67 for ; Thu, 25 Mar 2010 08:25:05 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by abelian.netcom.co.uk (8.13.1/8.13.1) with ESMTP id o2P8RnXF008336 for ; Thu, 25 Mar 2010 08:27:49 GMT Message-ID: <4BAB1E85.1060304@abelian.org> Date: Thu, 25 Mar 2010 08:27:49 +0000 From: Paul Nicholson User-Agent: Thunderbird 2.0.0.14 (X11/20080421) MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <4B9FD008.2070607@abelian.org> <4BAAA535.4050401@toya.net.pl> In-Reply-To: <4BAAA535.4050401@toya.net.pl> X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: Ionospheric VLF propagation Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=FROM_ENDS_IN_NUMS 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: 3039ac1d40554bab1ecd69ac X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) Piotr Mlynarski wrote: > one can mention the semiempirical Austin equation describing > E field dependence upon distance based on the idea of a > spatial waveguide: earth-ionosphere. That's a step forward. Up to now we've tried B = sqrt( 9.5e-21 * ERP/r) * exp( -r/a) where a = 2.9e6 for daytime path, or 4.3e6 for nighttime path. This assumes radiated power is spread uniformly over the circumference of a cylinder expanding across a flat earth, and the signal is trapped between earth and 70km ionosphere. I can see that an extra factor involving alfa/sin(alfa) (alfa = r/earth_radius) will be necessary to allow for spherical earth. Piotr, I've just found your post of 29th Jan, I'll go read that now... thanks for the tip. -- Paul Nicholson --