X-GM-THRID: 1219400842795700733 X-Gmail-Labels: rsgb lf X-Gmail-Received: c1de5f46d75b9857aadae5d5adb9fd1b4e97aee1 Delivered-To: daveyxm@gmail.com Received: by 10.78.127.1 with SMTP id z1cs55436huc; Tue, 7 Nov 2006 10:45:48 -0800 (PST) Received: by 10.67.100.17 with SMTP id c17mr9515248ugm.1162925148549; Tue, 07 Nov 2006 10:45:48 -0800 (PST) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id 59si6777931ugf.2006.11.07.10.45.47; Tue, 07 Nov 2006 10:45:48 -0800 (PST) Received-SPF: neutral (google.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1GhVs0-0006rD-ST for rs_out_1@blacksheep.org; Tue, 07 Nov 2006 18:40:24 +0000 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1GhVs0-0006r4-EP for rsgb_lf_group@blacksheep.org; Tue, 07 Nov 2006 18:40:24 +0000 Received: from post-25.mail.nl.demon.net ([194.159.73.195]) by relay2.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1GhVrx-00067f-DP for rsgb_lf_group@blacksheep.org; Tue, 07 Nov 2006 18:40:24 +0000 Received: from ndb.demon.nl ([82.161.81.65]:10878 helo=PCRoelof) by post-25.mail.nl.demon.net with smtp (Exim 4.51) id 1GhVrw-000CN6-FF for rsgb_lf_group@blacksheep.org; Tue, 07 Nov 2006 18:40:20 +0000 Message-ID: <003b01c7029c$267f7730$2101a8c0@PCRoelof> From: "Roelof Bakker" To: References: <6.1.1.1.2.20061107151228.07979730@mail.casema.nl> Date: Tue, 7 Nov 2006 19:40:08 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 X-Spam-Score: -0.4 (/) X-Spam-Report: autolearn=disabled,AWL=-0.368 Subject: LF: Re: DSP-filter for aural CW Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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 Status: O X-Status: X-Keywords: X-UID: 3726 Hello Dick, PA0LQ's filter is now in wide spread use amongst NDB afficiados in favour of DSP filters. By increasing the 10 nF capacitors to 27 nF and "stagger tuning" it has been possible to reduce the bandwidth from 30 Hz to 6 Hz with steep slopes. At present I am using two of these filters in cascade, 12 Hz and 6 Hz wide at a centre frequency of 500 Hz. The fixed tuning resistors have been replaced by multiturn trimmers of 1 K. Aligning section 1 and 3 for maximum signal at 495 Hz and section 2 and 4 at 505 Hz, yields a 3 dB bandwidth of 10 Hz. This is wide enough to copy 20 WPM morse code. Best regards, Roelof Bakker, pa0rdt