Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_MED,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: : mailn 1480; Body=3 Fuz1=3 Fuz2=3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v46HCXpx022965 for ; Sat, 6 May 2017 19:12:35 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1d73DF-0003gZ-U6 for rs_out_1@blacksheep.org; Sat, 06 May 2017 18:09:45 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1d73DF-0003gQ-L9 for rsgb_lf_group@blacksheep.org; Sat, 06 May 2017 18:09:45 +0100 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1d73DC-0003wW-W2 for rsgb_lf_group@blacksheep.org; Sat, 06 May 2017 18:09:44 +0100 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id 6909B208F7 for ; Sat, 6 May 2017 19:09:42 +0200 (CEST) Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 3wKwH95X6wzypd for ; Sat, 6 May 2017 19:09:41 +0200 (CEST) Message-ID: <590E0355.10609@posteo.de> Date: Sat, 06 May 2017 19:09:41 +0200 From: DK7FC User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <15bd53dda31-14f8-1cb1c@webprd-m59.mail.aol.com> <590B9892.9010406@posteo.de> <1493995971.279577405@f347.i.mail.ru> <590CA917.70808@posteo.de> <590CEE68.4000507@posteo.de> In-Reply-To: X-Scan-Signature: e6de17d69e46ff4ea8db042ef2cd7e46 Subject: Re: VLF: tonite on the 36km band... 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 2.75 Status: RO X-Status: X-Keywords: X-UID: 11609 Am 06.05.2017 18:17, schrieb Paul Nicholson: > > > These seem to be typical, where the decode goes astray for > several characters, then comes back. It seems to involve > runs of about 3 to 5 constraint lengths (eg 4 * 19 = 76 bits = > ~13 chars). Such a run contains 3 to 5 bits of redundancy in > the source encoding (0.3 bits per char) which the list decoder > makes use of. Putting in a small CRC allows the list decoder > to discard these 'diversions'. False decodes aren't much > of a problem because usually the real decode comes in with a > higher path metric and trumps the false ones but sometimes a > false decode wins. A small CRC will kill these off. > > For short messages, a very small or zero CRC remains best, > because of the significant inner code overhead. Interesting. Yes that sounds good. For short messages, the symbol length is usually smaller anyway, so a few bits more do not change the duration of the transmission. On the other side, many CRC bits in short messages (2 chars) make a very significant part of the whole transmission. I just saw that on my last announcement, decreased CRC from 32 to 2 and increasing the symbol length from 40 to 60 still results in a shorter duration!! > This also means I have to revise my policy for calculating an > optimum list length. Later I'll update the signal calculator > web page. Will see if i can see a difference then... 73, Stefan > > -- > Paul Nicholson > -- >