Return-Path: Received: (qmail 11699 invoked from network); 23 Jan 2001 09:39:33 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by 10.226.25.101 with SMTP; 23 Jan 2001 09:39:33 -0000 Received: (qmail 6375 invoked from network); 23 Jan 2001 09:43:00 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 23 Jan 2001 09:43:00 -0000 Content-Transfer-Encoding: 8bit Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14KzrG-0007j6-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 23 Jan 2001 09:35:22 +0000 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14KzrE-0007j1-00 for rsgb_lf_group@blacksheep.org; Tue, 23 Jan 2001 09:35:20 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id JAA31117; Tue, 23 Jan 2001 09:36:29 GMT Received: (qmail 32552 invoked from network); 23 Jan 2001 10:28:40 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 23 Jan 2001 10:28:40 -0000 Received: by gauntlet.mail.dera.gov.uk; id KAA25014; Tue, 23 Jan 2001 10:20:04 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma024808; Tue, 23 Jan 01 10:18:56 GMT Received: from FRN-MAIL-3.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Tue, 23 Jan 2001 09:37:09 +0000 Received: by frn-mail-3.dera.gov.uk with Internet Mail Service (5.5.2650.21) id ; Tue, 23 Jan 2001 09:33:54 -0000 Message-ID: <65AECDF1F89AD411900400508BFC869F0D7549@pdw-mail-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: LF: RE: Accuracy of Soundcards, programs, and related stuff Date: Tue, 23 Jan 2001 09:33:52 -0000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Is it a coincidence I wonder, that the 'standard' Soundcard / CD sampling rate is a multiple of the squares of the small prime numbers. ie: 44100 = 2 * 2 * 3 * 3 * 5 * 5 * 7 * 7 Spooky ! Certainly simplifies decimation to a wide variey of lower rates. For a CW tone centred on 800Hz, 11025 / 5 = 2205Hz would be ideal, letting a CW filter of up to 400Hz bandwidth handle removal of the aliasing products above 1102Hz. or 44100 / 5 = 8820 for a more accurate value for voice bandwidth signals. Andy G4JNT > 2.) Also stay away from all sample rates except 11025, 22050 or 44100 samples > per second. > If you need lower sample rates, decimate the input signal by two or three. If > the input spectrum does not contain frequencies above half of the *decimated* > sample rate, you don't even need a proper software-based anti-alias filter> -- The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.