Return-Path: Received: (qmail 29322 invoked from network); 17 Jan 2003 19:42:06 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 17 Jan 2003 19:42:06 -0000 Received: (qmail 21537 invoked from network); 17 Jan 2003 19:43:29 -0000 Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 17 Jan 2003 19:43:29 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.12) id 18ZcNE-0001me-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 17 Jan 2003 19:41:52 +0000 Received: from [210.86.15.144] (helo=mta201-rme.xtra.co.nz) by post.thorcom.com with esmtp (Exim 4.12) id 18ZcND-0001mV-00 for rsgb_lf_group@blacksheep.org; Fri, 17 Jan 2003 19:41:51 +0000 Received: from mta1-rme.xtra.co.nz ([210.86.15.142]) by mta201-rme.xtra.co.nz with ESMTP id <20030117194118.SHKE1191.mta201-rme.xtra.co.nz@mta1-rme.xtra.co.nz> for ; Sat, 18 Jan 2003 08:41:18 +1300 Received: from xtr743187 ([210.54.99.25]) by mta1-rme.xtra.co.nz with SMTP id <20030117194117.MSNH15912.mta1-rme.xtra.co.nz@xtr743187> for ; Sat, 18 Jan 2003 08:41:17 +1300 Message-ID: <004d01c2be60$d37b3480$196336d2@xtr743187> From: "Vernall" To: rsgb_lf_group@blacksheep.org References: <000701c2be0d$16426ee0$6507a8c0@Main> Date: Sat, 18 Jan 2003 08:44:17 +1300 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Notch for DCF39 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=0.5 required=6.0tests=REFERENCES,SPAM_PHRASE_00_01,USER_AGENT_OEversion=2.43 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Alan G3NYK, OK on the notch filter design, but for a high impedance load. I have often wanted to try a notch filter in a low impedance feeder, for such purposes as reducing a TV line oscillator harmonic or other carrier type of unwanted signal that is a few kHz from the wanted signal, as the unwanted carrier can paralyse a noise blanker from working effectively (the bandwidth of the noise blanker is necessarily relatively wide). On searching for information on notch filters I found a very good series of articles in Wireless World. Part 2 of the series in September 1979 deals with low impedance notch filters. The circuit used in "example 4" is a variant of what you used, with L and C in the leg to ground. If you can locate old copies of WW you could try modelling a low impedance notch filter. 73, Bob ZL2CA