Return-Path: X-Spam-DCC: paranoid 1169; 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=-2.6 required=5.0 tests=BAYES_00 autolearn=unavailable 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 s78HwdCc027169 for ; Fri, 8 Aug 2014 19:58:39 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1XFoNk-00068Z-34 for rs_out_1@blacksheep.org; Fri, 08 Aug 2014 18:55:12 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1XFoNj-00068Q-On for rsgb_lf_group@blacksheep.org; Fri, 08 Aug 2014 18:55:11 +0100 Received: from smtp-vbr15.xs4all.nl ([194.109.24.35]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.82) (envelope-from ) id 1XFoNi-00073y-87 for rsgb_lf_group@blacksheep.org; Fri, 08 Aug 2014 18:55:10 +0100 Received: from pc-roelof (ndb.demon.nl [82.161.81.65]) (authenticated bits=0) by smtp-vbr15.xs4all.nl (8.13.8/8.13.8) with ESMTP id s78Ht8su075293 for ; Fri, 8 Aug 2014 19:55:08 +0200 (CEST) (envelope-from roelof@ndb.demon.nl) To: rsgb_lf_group@blacksheep.org References: <095C9D4E586E45CAA3FE071EA4EA9818@HPG5401fr> <53E0F872.3030500@gmail.com> <64A3B1F0647248229C5C374887AA2FCB@F6CNI> <53E1EC0B.2060309@gmail.com> <1686C40AF97B4ABE99024972373C232A@HPG5401fr> <96662FC1BCA8402098A702D935EEC66F@F6CNI> <9556CA31D58145AFA57960399F67FE98@Clemens0811> Date: Fri, 08 Aug 2014 19:55:08 +0200 MIME-Version: 1.0 From: "Roelof Bakker" Message-ID: In-Reply-To: <9556CA31D58145AFA57960399F67FE98@Clemens0811> User-Agent: Opera Mail/1.0 (Win32) X-Virus-Scanned: by XS4ALL Virus Scanner X-Scan-Signature: c1f72e5acb1277e013f90c915ad7ad68 Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes Subject: Re: LF: RE: Re: Testing now a new RX antenna on MF 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: 185 Hello Clemens, > E.g., if your FFT is set to a bin width of say 5Hz and a carrier lies > 20dB over > the DANL (displayed average noise level) it will have a SNR of zero dB > in a > 500Hz "IF"-bandwidth and therefore will be barely audible. The brain of a skilled listener can simulate a bandpass filter with a width of 50 Hz. Hence your FFT bin width of say 5Hz and a carrier of 20dB over DANL will be clearly audible. Unfortunately the human brain needs white noise to work against, so a band full of interfering signals will exhaust the listener before long. On a quiet band it works great. This problem is solved by using a filter bandwidth of 10 - 20 Hz for aural copy of Morse Code. I believe that the "human brain filter bandwidth" is frequency dependent. When I started chasing NDB's, a beat note of 500 Hz was used. Over time this has changed to 300 Hz! Such a low beat note can be a problem with an analogue receiver due to less than perfect filter skirts. With SDR's the problem does not exist. 73, Roelof, PAoRDT