Return-Path: X-Spam-DCC: paranoid 1356; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.5 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,RATWARE_GECKO_BUILD autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u3UBLZGA006790 for ; Sat, 30 Apr 2016 13:21:35 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1awStK-0004gl-04 for rs_out_1@blacksheep.org; Sat, 30 Apr 2016 12:16:54 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1awStJ-0004gc-GY for rsgb_lf_group@blacksheep.org; Sat, 30 Apr 2016 12:16:53 +0100 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.87) (envelope-from ) id 1awStH-000232-MP for rsgb_lf_group@blacksheep.org; Sat, 30 Apr 2016 12:16:52 +0100 Received: from pn.abelian.org (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by parrot.netcom.co.uk (Postfix) with ESMTP id DD5C33273E4 for ; Sat, 30 Apr 2016 12:15:37 +0100 (BST) Received: from [127.0.0.1] (localhost [127.0.0.1]) by pn.abelian.org (Postfix) with ESMTP id 0106A400048 for ; Sat, 30 Apr 2016 11:16:50 +0000 (UTC) To: rsgb_lf_group@blacksheep.org References: <1546137dc25-12a6-35ed@webprd-a101.mail.aol.com> <57237FB9.2060507@posteo.de> <5723D581.1080403@posteo.de> From: Paul Nicholson Message-ID: <57249421.4060900@abelian.org> Date: Sat, 30 Apr 2016 11:16:49 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <5723D581.1080403@posteo.de> X-Scan-Signature: e6de17d69e46ff4ea8db042ef2cd7e46 Subject: Re: VLF: EbNaut for QSOs, beaconing and grabbers (?) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.11 Status: O X-Status: X-Keywords: X-UID: 7946 An interesting and challenging long-term experiment would be to watch for whistler mode propagation. Needs a beacon sending a pseudo-random test pattern (which could be an EbNaut message or just a block of random bits). The idea is that some of the signal will get into a whistler duct and travel through the magnetosphere to the geomagnetic conjugate, there to reflect from the top of the ionosphere and return back along the same path. A receiver might be able to pick up this echo with a delay of a second or two, and it could be detected by cross-correlation with the transmitted pattern. The pattern bits would have to be fairly rapid with respect to the echo delay, and the power level would have to be sufficient to detect the echo over an integration time short enough for the duct to remain phase stable - perhaps only a few minutes. Normally, whistler ducts are only detectable when there is a lightning storm at one end, but they are present whenever there is any geomagnetic disturbance. A beacon would be able to detect them at any time. With a good duct, multiple echoes can be heard as the signal repeatedly bounces back and forth through the duct. A recent example received at Todmorden, http://abelian.org/vlf/1460915680_27047.png shows a fairly exceptional case where there are at least 14 echoes. Dispersion in the duct (lower frequencies travel more slowly) is apparent, as is the low-loss nature of the duct. -- Paul Nicholson --