Delivered-To: daveyxm@virginmedia.com Received: by 10.50.96.198 with SMTP id du6csp255464igb; Tue, 3 Dec 2013 06:01:39 -0800 (PST) X-Received: by 10.194.173.163 with SMTP id bl3mr59773737wjc.10.1386079298556; Tue, 03 Dec 2013 06:01:38 -0800 (PST) Return-Path: Received: from post.thorcom.com (post.thorcom.com. [195.171.43.25]) by mx.google.com with ESMTP id m7si918254wik.84.2013.12.03.06.01.37 for ; Tue, 03 Dec 2013 06:01:38 -0800 (PST) Received-SPF: neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) client-ip=195.171.43.25; Authentication-Results: mx.google.com; spf=neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) smtp.mail=owner-rsgb_lf_group@blacksheep.org; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Vnq2R-00014e-MA for rs_out_1@blacksheep.org; Tue, 03 Dec 2013 13:29:19 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Vnq2R-00014V-4U for rsgb_lf_group@blacksheep.org; Tue, 03 Dec 2013 13:29:19 +0000 Received: from mail-ea0-f177.google.com ([209.85.215.177]) by relay1.thorcom.net with esmtps (TLSv1:RC4-SHA:128) (Exim 4.77) (envelope-from ) id 1Vnq2P-00054T-HV for rsgb_lf_group@blacksheep.org; Tue, 03 Dec 2013 13:29:18 +0000 Received: by mail-ea0-f177.google.com with SMTP id n15so9833133ead.8 for ; Tue, 03 Dec 2013 05:29:16 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:content-type:message-id:mime-version:subject:date:references :to:in-reply-to; bh=KmAny8DQKeldCgKCavDm1OHVftXcnzs9asB32b6zylc=; b=0uVDUWJxd8NEJFFb0SCzJh3H1ybyM6Qh2Cx1hL4abGX2uEuyzVn1a/3wFzUzMBXFEf IYwSasKBQbPcJ20XoteQGPWAekw2h5ww6KQdx0kM/yzqDmzejsic3rph8CrXCDD9Y3Pf C3LzyA/LvRfvb3uixdEhkG0APlGeOu3/LSLNoBB0eodep8A5v9rybGDcXpw/MjcVeK/R 5rIgaMX3hHof16m6sUhrFemnmIHkynUdP20yC7xDgZy/PxlqKnjJ3J9kVgy9ssVa2fpd gXHE5Hs/FNcnjWS/OgGdDfjQFSpmSudjvDQ+49rBKRy1iEicHgZuHcrYNsykhKkG6JjZ YbHQ== X-Received: by 10.15.33.139 with SMTP id c11mr2762793eev.110.1386077356528; Tue, 03 Dec 2013 05:29:16 -0800 (PST) Received: from [192.168.1.103] ([217.67.155.178]) by mx.google.com with ESMTPSA id m1sm76764878eeg.0.2013.12.03.05.29.15 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 03 Dec 2013 05:29:15 -0800 (PST) From: John Rabson Message-Id: <63AC3ACD-CC59-4EAC-A935-8E776E4F8F4A@gmail.com> Mime-Version: 1.0 (Mac OS X Mail 7.0 \(1822\)) Date: Tue, 3 Dec 2013 14:29:13 +0100 References: <45EA2FEA-74E3-4AB1-A37B-868C7F526EF0@gmail.com> <143c01cef008$56bc7900$04356b00$@comcast.net> To: rsgb_lf_group@blacksheep.org In-Reply-To: <143c01cef008$56bc7900$04356b00$@comcast.net> X-Mailer: Apple Mail (2.1822) X-Spam-Score: -0.4 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: I think I understand the term “dispersion” in the optical context and how there could be a similar mechanism at VLF. My main reasons for posting are: 1) an interest is reduced-bandwidth speech systems at cave radio frequencies (typically 87 kHz) 2) the resilience of such systems when used in the presence of impulsive interference such as LORAN – a problem which is widespread in north-west Europe 3) there are also systems which work at VLF and are intended for subterranean location. A typical carrier frequency appears to be of the order of 3 kHz, and I wonder if a simple SSB system on 3.3 kHz USB system might give useful range (a few hundred metres) for voice communication. 4) Some Australian amateurs have been experimenting with digital voice systems (codec2?) on HF and it seems to be possible this approach might also be useful. [...] Content analysis details: (-0.4 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.215.177 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (john.rabson07[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.2 FREEMAIL_ENVFROM_END_DIGIT Envelope-from freemail username ends in digit (john.rabson07[at]gmail.com) 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: c9d6a1e47761f7ec7375ac340bef30d0 Content-Type: multipart/signed; boundary="Apple-Mail=_FA30C416-06BD-477F-AD96-01106FED5B18"; protocol="application/pgp-signature"; micalg=pgp-sha512 Subject: Re: LF: RE: Article on VLF 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 Status: O X-Status: X-Keywords: X-UID: 2650 --Apple-Mail=_FA30C416-06BD-477F-AD96-01106FED5B18 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 I think I understand the term =93dispersion=94 in the optical context = and how there could be a similar mechanism at VLF. My main reasons for = posting are: 1) an interest is reduced-bandwidth speech systems at cave radio = frequencies (typically 87 kHz) 2) the resilience of such systems when used in the presence of impulsive = interference such as LORAN =96 a problem which is widespread in = north-west Europe 3) there are also systems which work at VLF and are intended for = subterranean location. A typical carrier frequency appears to be of the = order of 3 kHz, and I wonder if a simple SSB system on 3.3 kHz USB = system might give useful range (a few hundred metres) for voice = communication. 4) Some Australian amateurs have been experimenting with digital voice = systems (codec2?) on HF and it seems to be possible this approach might = also be useful. John F5VLF On 3 Dec 2013, at 10:16CET, hvanesce wrote: > It might be informative to consider exploitation and mitigation of > dispersion in approaches to compression for VLF links. >=20 > Jim AA5BW=20 >=20 --Apple-Mail=_FA30C416-06BD-477F-AD96-01106FED5B18 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQEcBAEBCgAGBQJSndypAAoJEKzwAOXC9Is4DK4IAIIzZ19CCqff/2LpX8yAkQGf ulhHV0/BsoeD6edoVVmCT/CIWrc8DYQNWY8zUmahFD/u9L1M1ToFnhhm7fIKHJEh PztkXayXeZU24hh2qIX9AYJpRBF0w8c518B2zuyizncvGAAPZZ+F967YWP0rgLXW 1yRRTOlJsmp6A3FIrgBDOv8SN8dLXJfrUNmdDgTPdSKWTmQN2xjaxFWVntTSwAtd +xTXElRE6B76ikDezO0p6GBMBKE1EoKhlKf71hesrd0ebrhxtJRoTbM7hbOA1JDu E7/x6QiS9N1ISX+Hdfx5yxWavtloqCrxEX+ExW2gIBfiA3P8J6Lg02MfrkpXO9E= =eg9O -----END PGP SIGNATURE----- --Apple-Mail=_FA30C416-06BD-477F-AD96-01106FED5B18--