Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id vBBAlTJf025118 for ; Mon, 11 Dec 2017 11:47:30 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1eOLWy-0006qa-CS for rs_out_1@blacksheep.org; Mon, 11 Dec 2017 10:41:52 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1eOLWx-0006qR-Oz for rsgb_lf_group@blacksheep.org; Mon, 11 Dec 2017 10:41:51 +0000 Received: from porthos.netcom.co.uk ([217.72.171.73]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eOLWu-0003ET-IF for rsgb_lf_group@blacksheep.org; Mon, 11 Dec 2017 10:41:50 +0000 X-DKIM-Result: Domain=abelian.org Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=abelian.org ; s=default; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=purau0vl2tC/JUkN54cbxdZ2/96gaLDcjMWfeXG6f1E=; b=u6H+gQ3UP9wRAcPiLYrP2Gaxxv oqsCu2RJAXA5pVWx4OlvdVsfurywcEpSKDKp10Thz9ZqYT+x3YIEJvPrMgSekUonLc6TrB37P8vop qsQUb4ZGVGSrjvJOidTvHc2JLWXDfd+A/mftpl5x08O2AWDoQHk5ZEOqzKO2TjUZ4UoA=; Received: from i-194-106-52-83.freedom2surf.net ([194.106.52.83]:34878 helo=pn.abelian.org) by porthos.netcom.co.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eOLWs-0004D9-Tm; Mon, 11 Dec 2017 10:41:47 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) by pn.abelian.org (Postfix) with ESMTP id 457F1400215; Mon, 11 Dec 2017 10:41:46 +0000 (UTC) To: rsgb_lf_group@blacksheep.org Cc: Michael Smith References: <2dbcd2a8-0109-41e4-c0ca-aada17f54de8@abelian.org> From: Paul Nicholson Message-ID: <1fc8e54e-50f6-3fef-ee8c-f8848304f719@abelian.org> Date: Mon, 11 Dec 2017 10:41:46 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - porthos.netcom.co.uk X-AntiAbuse: Original Domain - blacksheep.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - abelian.org X-Get-Message-Sender-Via: porthos.netcom.co.uk: authenticated_id: catchall@abelian.org X-Authenticated-Sender: porthos.netcom.co.uk: catchall@abelian.org X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Jacek wrote: > could you give a short explanation? i don't really understand > nonreciprocal propagation I don't either, really. The ionospheric reflection coefficient depends on the direction of the radio wave relative to the Earth's magnetic field. The wave accelerates free electrons in the plasma, and they're pulled into circular or helical paths by the magnetic field. This alters the phase of the reflection and the attenuation of the wave through energy loss by collisions. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 0b36c952c26be93e626fe2fa1c93657f Subject: Re: VLF: Transatlantic success East to West 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 Jacek wrote: > could you give a short explanation? i don't really understand > nonreciprocal propagation I don't either, really. The ionospheric reflection coefficient depends on the direction of the radio wave relative to the Earth's magnetic field. The wave accelerates free electrons in the plasma, and they're pulled into circular or helical paths by the magnetic field. This alters the phase of the reflection and the attenuation of the wave through energy loss by collisions. The consequence is the reflection coefficient isn't a nice simple number, it's a 2x2 matrix with each component a (frequency dependent) complex number. It's all the in Appleton-Hartree equations https://en.wikipedia.org/wiki/Appleton%E2%80%93Hartree_equation which are quite easy to calculate and program (easier than they look at first glance) but few people would admit to understanding them. Spent some time with LWPC measuring the T/A path at some different frequencies. The figures below are the extra loss on the east-to-west, compared with west-to-east. The results don't depend much on which end points I choose, but are quite frequency dependent: Midnight UTC: 18.0 kHz: 2 dB 17.4 kHz: 3 dB 16.5 kHz: 6 dB 16.0 kHz: 9 dB 15.0 kHz: 14 dB 14.0 kHz: 18 dB 13.0 kHz: 16 dB 12.0 kHz: 13 dB 11.0 kHz: 11 dB 10.0 kHz: 10 dB 9.0 kHz: 10 dB 8.2 kHz: 12 dB 5.2 kHz: 27 dB 4.2 kHz: 44 dB 2.9 kHz: LWPC doesn't run Generally a lot more anisotropy as the frequency drops, but there's a funny peak around 14 kHz. Midday UTC: 18.0 kHz: 4 dB 17.4 kHz: 4 dB 16.0 kHz: 5 dB 15.0 kHz: 5 dB 14.0 kHz: 6 dB 13.0 kHz: 7 dB 12.0 kHz: 8 dB 11.0 kHz: 9 dB 10.0 kHz: 10 dB 9.0 kHz: 12 dB 8.2 kHz: 14 dB 5.2 kHz: 35 dB 4.2 kHz: no output from LWPC The funny peak vanishes during the day. So, nowhere near as much anisotropy as I thought at 17.4 kHz. I don't fancy our chances at the lower VLF bands - it might be easier to take the long path! -- Paul Nicholson --