X-GM-THRID: 1219400842795700733 X-Gmail-Labels: rsgb lf X-Gmail-Received: 09c98958223d01ee417959e08ef631407f747708 Delivered-To: daveyxm@gmail.com Received: by 10.78.127.1 with SMTP id z1cs70956huc; Tue, 7 Nov 2006 13:25:43 -0800 (PST) Received: by 10.67.22.14 with SMTP id z14mr9749600ugi.1162934742821; Tue, 07 Nov 2006 13:25:42 -0800 (PST) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id 32si6954442ugf.2006.11.07.13.25.40; Tue, 07 Nov 2006 13:25:42 -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 1GhYN1-0007Hb-Ty for rs_out_1@blacksheep.org; Tue, 07 Nov 2006 21:20:35 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1GhYMz-0007HS-7o for rsgb_lf_group@blacksheep.org; Tue, 07 Nov 2006 21:20:33 +0000 Received: from rwcrmhc15.comcast.net ([204.127.192.85]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1GhYMw-0005xF-Bk for rsgb_lf_group@blacksheep.org; Tue, 07 Nov 2006 21:20:33 +0000 Received: from rmailcenter06.comcast.net ([204.127.197.116]) by comcast.net (rwcrmhc15) with SMTP id <20061107212023m1500bsb35e>; Tue, 7 Nov 2006 21:20:23 +0000 Received: from [24.91.125.179] by rmailcenter06.comcast.net; Tue, 07 Nov 2006 21:20:22 +0000 From: k2ors@comcast.net (Warren K2ORS/WD2XGJ/WD2XSH/23) To: rsgb_lf_group@blacksheep.org, Cc: "Roelof Bakker" Date: Tue, 07 Nov 2006 21:20:22 +0000 Message-Id: <110720062120.13773.4550F89600039AAC000035CD22007348300B97010D0A020E06979D0E03@comcast.net> X-Mailer: AT&T Message Center Version 1 (Oct 4 2006) X-Authenticated-Sender: bWFyeWphbmVib3lkQGNvbWNhc3QubmV0 X-Spam-Score: 0.9 (/) X-Spam-Report: autolearn=disabled,AWL=-1.442,DNS_FROM_RFC_POST=1.44,DNS_FROM_RFC_WHOIS=0.879 Subject: Re: LF: Re: DSP-filter for aural CW 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: 3725 Roelof, Where can I find plans for the PA0LQ filter? Thanks, -- 73 Warren K2ORS/WD2XGJ/WD2XSH/23 FN42hi http://www.w4dex.com/wd2xgj.htm -------------- Original message ---------------------- From: "Roelof Bakker" > 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 > > >