Return-Path: X-Spam-DCC: paranoid 1233; 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=-0.8 required=5.0 tests=BAYES_00,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 sBMM4aBM007413 for ; Mon, 22 Dec 2014 23:04:36 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Y3B0R-0001jc-6k for rs_out_1@blacksheep.org; Mon, 22 Dec 2014 21:59:11 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Y3B0Q-0001jP-SR for rsgb_lf_group@blacksheep.org; Mon, 22 Dec 2014 21:59:10 +0000 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.84) (envelope-from ) id 1Y3B0L-0000y5-FR for rsgb_lf_group@blacksheep.org; Mon, 22 Dec 2014 21:59:09 +0000 Received: from sb.abelian.org (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by parrot.netcom.co.uk (Postfix) with ESMTP id 523B63273F4 for ; Mon, 22 Dec 2014 21:57:59 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by sb.abelian.org (Postfix) with ESMTP id 85DE428A0726 for ; Mon, 22 Dec 2014 21:59:03 +0000 (UTC) Message-ID: <54989427.4020505@abelian.org> Date: Mon, 22 Dec 2014 21:59:03 +0000 From: Paul Nicholson User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <0f8ae05d3ad24aabaae803b8e887c042@kabelmail.de> In-Reply-To: <0f8ae05d3ad24aabaae803b8e887c042@kabelmail.de> X-Scan-Signature: 1708620d3ce65bee0beaaede7929769a Subject: Re: VLF: 8270 Hz BPSK Content-Type: text/plain; charset=ISO-8859-1; 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 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 1579 Uwe wrote: > I would prefer Rate 1/8K = 25 out of your convolution code > message generator, i.e. 560bits in 4h40min. Your last transmission I think was on 2014-11-07 and I just examined the recording: You were S/N 14.7dB in 278uHz between 12:00 and 14:00. Signal is strong enough to send data quite fast. You could use 14 second symbols to send 10 characters (800 signal bits in 03:06:40) for a virtually certain decode. A more challenging test with 11 second symbols would still have 95% chance of correct decode. So far the best radio amateur message transmission at VLF was by Markus DF6NM on 2014-05-18 when he sent 14 characters across 1028km. If we use product of distance and characters as a metric then that's a score of 14392 kmchars. At 762km you would have to send 19 or more characters to beat that. Daytime should allow a 4 hour message without trouble. Rate 1/8, 11 second symbols, 21 characters (1328 bits in 04:03:28). Avoid the terminators. Send around midday +/- 2 hours. On 2014-12-14 I wrote: > http://abelian.org/vlf/tmp/141219c.png > From 00:00 to 08:00 it averaged 12.6dB S/N in 278uHz, 0.14fT. > That's enough signal to send 27 characters at a rate of 22 > information bits per hour. I gave this a test using a recording of W4DEX carrier from that night. Modulating the recording with a BPSK message 27 characters long, rate 1/16 K=25 with a symbol period of only 7.5 seconds and it decoded correctly with a small margin to spare. 9 second symbols decoded with plenty of margin. -- Paul Nicholson http://abelian.org/ --