Return-Path: X-Spam-DCC: paranoid 1102; 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=-1.6 required=5.0 tests=BAYES_00,NO_REAL_NAME 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 t05Mo0R0009742 for ; Mon, 5 Jan 2015 23:50:00 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Y8GNX-0005RB-93 for rs_out_1@blacksheep.org; Mon, 05 Jan 2015 22:44:03 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Y8GNW-0005R1-R3 for rsgb_lf_group@blacksheep.org; Mon, 05 Jan 2015 22:44:02 +0000 Received: from resqmta-po-02v.sys.comcast.net ([96.114.154.161]) by relay1.thorcom.net with esmtps (TLSv1.2:DHE-RSA-AES256-SHA:256) (Exim 4.84) (envelope-from ) id 1Y8GNU-0000u1-NL for rsgb_lf_group@blacksheep.org; Mon, 05 Jan 2015 22:44:01 +0000 Received: from resomta-po-13v.sys.comcast.net ([96.114.154.237]) by resqmta-po-02v.sys.comcast.net with comcast id cNjf1p00157bBgG01NjxEF; Mon, 05 Jan 2015 22:43:57 +0000 Received: from Owner ([166.171.250.255]) by resomta-po-13v.sys.comcast.net with comcast id cNjn1p00b5XNVT201NjrPU; Mon, 05 Jan 2015 22:43:55 +0000 X-DKIM-Result: Domain=comcast.net Result=Signature OK From: To: References: <54AB0110.3030709@abelian.org> In-Reply-To: <54AB0110.3030709@abelian.org> Date: Mon, 5 Jan 2015 14:43:34 -0800 Message-ID: <013401d02939$14569e40$3d03dac0$@comcast.net> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQFWdfAUeO5esHKAaJJDePUuoab/RQINLAg9nZUL0wA= Content-Language: en-us DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20140121; t=1420497837; bh=L4mxR02B7UBYjazSrJzoN1HoTIFoPrhQhN9kO4v4iHk=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=phPxIF1+MdigzSXGcWg6AoHB9/qGv5sberKzOlj5ubUiBYp9nShNHbD9qZDjG8SrU 7MbyJXHD9YyNjpSJR7wHQIyLflMmWC54IQP+APibzcc2IkH3eoTcbAOivEsNKjLiud 0rWiRtO04NZJt3FS/px8Mdcr3CT3M7jLxGv9KBVfvzaLmaSU6dDydK+nbx10ZV2I1E 2k+yofQOznpfjOafqcwGrI48xUgh3kKRJ3vjFx1aTrET30IMw7U2rqHL3nfYBzXh9o xsTPGhZN2qkoJZ5/AWfT0Bp+lN3Pt1seJN5tV3fjTwxMVLSVzwrnCLemMaxZjrBhw5 xMT2hPejeZiTQ== X-Scan-Signature: ead411ce91f9601ce3974c7575797436 Subject: RE: VLF: Transatlantic messages at 8822Hz Content-Type: text/plain; charset="us-ascii" 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 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 1816 Paul, Congratulations to you, Dex and the rest of the team on this work, including 73% channel capacity in the midst of many constraints! I had planned to ask if you thought that any atmospheric phase noise information might be implicit in the team's data from this experiment, for phase error spectral components anywhere near your information rate*. Your reconstructed-carrier information seems to answer that question, given that there are 4 inflection points in the phase trend from 00:00 to 07:00. I'm guessing that the multiple inflections could be manifestations of amplitude noise alone (given ~14dB SNR and < 7 degrees between inflections), such that any atmospheric phase noise estimate more accurate than (for example) ten degrees would need to be made over an interval of multiple hours; and that information (of precision better than ten degrees for example) on phase error spectral components near your information rate would therefore not be available from this most recent data. Is the reasoning above incorrect? Perhaps it's better to ask if channel capacity tests provide some unique value to phase error measurement: do encoding and comparison to the Shannon limit offer any potentially unique information regarding phase noise, notwithstanding low amplitude-SNR? Great experiments and results! 73, Jim AA5BW * (6.8E-3 bps for test 3 based on 24.6 bph?) -----Original Message----- From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Paul Nicholson Sent: Monday, January 5, 2015 1:25 PM To: rsgb_lf_group@blacksheep.org Subject: Re: VLF: Transatlantic messages at 8822Hz By reversing the modulation of Dex's Jan 1st transmission, the carrier is reconstructed. S/N and phase in in 1 hour (278uHz) steps: 00:00 to 01:00 11.6 dB -122.1 01:00 to 02:00 13.1 dB -119.4 02:00 to 03:00 12.6 dB -131.9 03:00 to 04:00 14.3 dB -135.0 04:00 to 05:00 12.7 dB -111.0 05:00 to 06:00 15.2 dB -118.9 06:00 to 07:00 13.4 dB -111.7 Average of above: 13.27 dB This agrees well with the S/N of 13.33 dB in 278uHz calculated from the symbol error rate. Note the steady phase which is what allows coherent BPSK to be used when the signal is too weak to extract a reference phase. The decoder merely has to try phases (in say 30 degree steps) until it gets a decode. I wrote: > information rate ... 80% of the channel capacity. I made a mistake and forgot to allow for the 16 CRC bits (they belong to the coding, not the information payload). Actually the rate was 73% of capacity. I suppose we'll just have to do better. In the same series of tests, I received a 9 character message from Markus DF6NM with symbol error rate 0.395, Es/N0 = -14.4dB, Eb/N0 = 0.0 dB at an effective code rate of 1/27.85. This achieved 71% of channel capacity. In fact it was quite an easy decode of the 10 second symbols (it did not require list decoding) and with hindsight we could have used 8.5 symbols to obtain 83% of capacity. This illustrates the challenge of selecting a symbol rate for any given test. It is essential to have some reliable carrier S/N measurements beforehand. Another result: On 30th December a 4 character message from W4DEX was decoded from the natural radio receiver at Sebring FL, distance 869 km. Eb/N0 was +2.8 dB so it was nowhere near the channel capacity and we could have used a much longer, faster message. I am very grateful to Markus and Dex for making these tests happen and turning what would have been just a computing exercise, into reality. It seems there are three essentials for success at VLF: Teamwork; A GPS; And the following advice - "Get started and see what happens... Turn your DREAM into REALITY!!" ...Mal Hamilton G3KEV, Feb 2010. -- Paul Nicholson http://abelian.org/ --