Return-Path: Received: (qmail 4322 invoked from network); 19 Feb 2001 18:14:12 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by 10.226.25.101 with SMTP; 19 Feb 2001 18:14:12 -0000 Received: (qmail 5669 invoked from network); 19 Feb 2001 18:14:15 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 19 Feb 2001 18:14:15 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 14Uujl-00087h-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 19 Feb 2001 18:08:37 +0000 X-Priority: 3 Received: from d06lmsgate-3.uk.ibm.com ([195.212.29.3]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 14Uujh-00087T-00 for rsgb_lf_group@blacksheep.org; Mon, 19 Feb 2001 18:08:36 +0000 X-MSMail-Priority: Normal Received: from d06relay01.portsmouth.uk.ibm.com (d06relay01.portsmouth.uk.ibm.com [9.166.84.147]) by d06lmsgate-3.uk.ibm.com (1.0.0) with ESMTP id RAA85226 for ; Mon, 19 Feb 2001 17:58:58 GMT Received: from usa.net (ss10.bld.socks.ibm.com [9.14.4.76]) by d06relay01.portsmouth.uk.ibm.com (8.8.8m3/NCO v4.95) with ESMTP id SAA55868 for ; Mon, 19 Feb 2001 18:07:35 GMT X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: <3A9160B5.D9C9DE4D@usa.net> Date: Mon, 19 Feb 2001 19:06:45 +0100 From: "Alberto di Bene" Organization: Undisclosed X-Mailer: Mozilla 4.76 [en] (Win95; U) X-Accept-Language: en MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org Subject: LF: Re: Signalling margins and Shannon References: <65AECDF1F89AD411900400508BFC869F0D75CC@pdw-mail-1.dera.gov.uk> Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 8bit Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Talbot Andrew wrote:

Has anyone looked at what Signal to Noise is realistically viewable on a spectrogram display ? Assuming bandwidth equal to FFT bin size, my few tests suggest around 10dB but it would be nice to have a more authoritative figure to calculate with. Obviously depends on colour palette and number of colours on the display so after a couple of years of experience with Spectrogram and now Argo, what has anyone found ?

Maybe those 10dB are a bit on the pessimistic side. Before writing Spectran and Argo, I used the FFTDSP program by AF9Y, which has
an S/N indicator. I remember having seen with it traces of signals whose S/N was reported being a couple of dBs.
Those of you who have calibrated signal sources could arrange a testing fixture to give more accurate values.

73 Alberto I2PHD