Return-Path: <majordom@post.thorcom.com> Received: (qmail 26524 invoked from network); 27 Jul 2002 08:28:04 -0000 Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 27 Jul 2002 08:28:04 -0000 Received: (qmail 19584 invoked from network); 27 Jul 2002 08:28:05 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 27 Jul 2002 08:28:05 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17YMpG-00040C-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 27 Jul 2002 09:21:22 +0100 Received: from e2.ny.us.ibm.com ([32.97.182.102]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 17YMpF-000407-00 for rsgb_lf_group@blacksheep.org; Sat, 27 Jul 2002 09:21:21 +0100 Received: from northrelay01.pok.ibm.com (northrelay01.pok.ibm.com [9.56.224.149]) by e2.ny.us.ibm.com (8.12.2/8.12.2) with ESMTP id g6R8Kne8141812 for <rsgb_lf_group@blacksheep.org>; Sat, 27 Jul 2002 04:20:49 -0400 Received: from usa.net (ss1.bld.socks.ibm.com [9.14.4.66]) by northrelay01.pok.ibm.com (8.12.3/NCO/VER6.3) with ESMTP id g6R8Ki0r044112 for <rsgb_lf_group@blacksheep.org>; Sat, 27 Jul 2002 04:20:47 -0400 Message-ID: <3D4257FC.CDC26C4D@usa.net> Date: Sat, 27 Jul 2002 10:21:16 +0200 From: "Alberto di Bene" <dibene@usa.net> Organization: None X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org Subject: LF: Re: Jason 0.94 tests References: <5.1.0.14.0.20020726140304.00ae6518@gemini.herts.ac.uk> <17YCsw-1DnzvMC@fwd01.sul.t-online.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: <majordom@post.thorcom.com> jannsen wrote: > Hi Jim, Alberto es all > > my report see attachment. conspicuous the spurii during the switchovers from > tone to tone. has Alberto an explanation ? Hello Uwe and the group, yes, there is an explanation. The waterfall window has a strong visual AGC applied, so to put into greater evidence the tone received. The AGC gain is computed only taking into consideration what falls inside the two yellow lines. Now picture into your mind the FFT buffer as a long glass tube, where coloured water enters from one side, flows all along the tube and exits from the other side. The water can have different colours, which correspond to the frequency of the incoming signals. Suppose a single frequency is arriving, corresponding to a red water colour. This is the predominant colour, your eye sees only it, unconsciously discarding spurious strikes of other colours. Now the tone changes. While the red water still flows towards the exit end of the tube, from the other end blue water is coming. Until the tube is full of only blue water, there will be a changing mixture of both colours in the tube, red slowly decreasing and blue increasing. In this condition, your eye is no more dominated by a single chromatic sensation, and you see the red, the blue and the other strikes. This also explains the blurring that can be seen, lets' say, in Spectran when receiving a DFCW signal and the tone changes. In this analogy your eye is the equivalent of the FFT processing, which is presented with the input buffer (the tube). It's not a perfect example, many things could be criticized, but I do hope it can explain a little what's happening. 73 Alberto I2PHD