Return-Path: Received: from mtain-di04.r1000.mx.aol.com (mtain-di04.r1000.mx.aol.com [172.29.64.8]) by air-di06.mail.aol.com (v127_r1.1) with ESMTP id MAILINDI061-eaca4b8816683d2; Fri, 26 Feb 2010 13:43:52 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-di04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 14E55380000A4; Fri, 26 Feb 2010 13:43:50 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Nl58w-0007sK-9p for rs_out_1@blacksheep.org; Fri, 26 Feb 2010 18:42:30 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Nl58v-0007sB-Uz for rsgb_lf_group@blacksheep.org; Fri, 26 Feb 2010 18:42:29 +0000 Received: from mx.omskcity.com ([79.133.160.2]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Nl58s-0007ya-TO for rsgb_lf_group@blacksheep.org; Fri, 26 Feb 2010 18:42:29 +0000 Received: from noname.nodomain.nowhere (host209.161-133-79.sotline.ru [79.133.161.209]) by mx.omskcity.com (8.13.6/8.13.6) with ESMTP id o1QIgMAq019787 for ; Sat, 27 Feb 2010 00:42:23 +0600 (OMST) (envelope-from fitec@omskcity.com) Received: from localhost (fitec@localhost) by noname.nodomain.nowhere (8.8.5/8.8.5) with SMTP id BAA00275 for ; Sat, 27 Feb 2010 01:47:25 GMT X-Authentication-Warning: noname.nodomain.nowhere: fitec owned process doing -bs Date: Sat, 27 Feb 2010 01:47:25 +0000 (GMT) From: "Alexander S. Yurkov" To: rsgb_lf_group@blacksheep.org In-Reply-To: Message-ID: MIME-Version: 1.0 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.1.8 (mx.omskcity.com [79.133.160.2]); Sat, 27 Feb 2010 00:42:24 +0600 (OMST) X-Spam-Score: 1.5 (+) X-Spam-Report: autolearn=disabled,DATE_IN_FUTURE_06_12=1.498 Subject: Re: LF: Re: 9kHz noise level Content-Type: TEXT/PLAIN; charset=US-ASCII X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.9 required=5.0 tests=DATE_IN_FUTURE_06_12 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d40084b88166614f4 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) On Fri, 26 Feb 2010, Andy Talbot wrote: > probably end up appearing quite close to Gaussian. Certainly, on 73kHz > the impulsive Loran interference and natural spikes appeared completely > Gaussian when filtered to the sub-Hz bandwidth we used there. Andy, certanly AFTER filtering noise became gaussian. But matter of fact is that if noise is nongaussian then to get optimal reception one should make some nonlinear processing (limiting in simplest way) BEFORE narrow band filtering. After filtering when noise is gaussian limiting or someone else nonliniar processing has no sence. There is exact matematical theorem: if noise is gaussian then optimal signal processing is linear filtering (or correlator calculation in coherent case). > However, for 9kHz signalling, I think you would do a lot better by going for > coherent signalling. IMHO coherent signaling improoves SNR by 3 dB. It does not depend of the fact if noise is gaussian or nongaussian. Anyway this (coherent signaling) is linear processing nonoptimal when noise is nongaussian. Interesting quation arises there. Is any optimal form of the signal if noise is nongaussian? I don't know answer. This is high science. But if noise is gaussian then form of the signal has no meaning. Only energy of the signal has meaning if noise is gaussian (with constant spectrum). If filter is optimal for specific signal of couse. Regards, Alexander/RA9MB