X-GM-THRID: 1234888028149353688 X-Gmail-Labels: rsgb lf Delivered-To: daveyxm@gmail.com Received: by 10.35.22.5 with SMTP id z5cs321183pyi; Fri, 27 Apr 2007 08:38:37 -0700 (PDT) Received: by 10.66.224.3 with SMTP id w3mr2137056ugg.1177688317407; Fri, 27 Apr 2007 08:38:37 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id e23si7244037ugd.2007.04.27.08.38.33; Fri, 27 Apr 2007 08:38:37 -0700 (PDT) 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) DomainKey-Status: good (test mode) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1HhSRL-00061H-5R for rs_out_1@blacksheep.org; Fri, 27 Apr 2007 16:32:55 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1HhSRK-000618-FE for rsgb_lf_group@blacksheep.org; Fri, 27 Apr 2007 16:32:54 +0100 Received: from wx-out-0506.google.com ([66.249.82.232]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1HhSRJ-0001yF-IP for rsgb_lf_group@blacksheep.org; Fri, 27 Apr 2007 16:32:54 +0100 Received: by wx-out-0506.google.com with SMTP id t12so964980wxc for ; Fri, 27 Apr 2007 08:32:52 -0700 (PDT) DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed; d=googlemail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=VYKTbOH13P3qhiQkMAL3wVMlSIJxlOuHUGPnLklLE4usW28FgfafsmwAH1EQt74gJE2s+C0PPtIG3Y6r5qlZEZlX0kAc1BBTCPH4n+xnfGcH8aqzlubYTokWTYmu9gaAVvyEO5SMAWyTdmPdkO0TYDQhauWm8HnBZaPK8E404i8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=EsQy4SUcSEVrRvO+qho+gEwa/YhqzgcXih4WYfVWYCJObVDqHikLaP0it/jE9kXNZX75I1XC2lJYV/+S3uFpBrpfM2FK3iakb1CTSrmmsKagl38DIg+MBXzcltsqlaXSTsNKiuH5GzmOprMAKi0e/hZ+RLN6ewxn5psNVU70SS8= Received: by 10.90.99.20 with SMTP id w20mr3547560agb.1177687972232; Fri, 27 Apr 2007 08:32:52 -0700 (PDT) Received: by 10.90.50.7 with HTTP; Fri, 27 Apr 2007 08:32:51 -0700 (PDT) Message-ID: Date: Fri, 27 Apr 2007 16:32:51 +0100 From: "Andy Talbot" To: rsgb_lf_group@blacksheep.org In-Reply-To: <001701c788d3$612266f0$6405a8c0@MJUSonyLaptop> MIME-Version: 1.0 References: <001701c788d3$612266f0$6405a8c0@MJUSonyLaptop> DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: RE: Filter expert needed - Mystery of the lost real zero. Content-Type: multipart/alternative; boundary="----=_Part_10563_8708612.1177687971916" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40, HTML_FONTCOLOR_UNKNOWN,HTML_MESSAGE 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: 2009 ------=_Part_10563_8708612.1177687971916 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline hi Mike - No I don't want a zero there. For all practical purposes I'm more than happy with what the filter actually does at the moment. My puzzle is that there should be one and there isn't. An inductor coupling non-adjacent resonators appears to put a zero into the pass band; at least it puts a huge dip there - the last thing I want. Andy G4JNT On 27/04/07, Mike Underhill wrote: > > Andy > > > > A correction: I should have said 'in series with' and not 'across'. So > that my post should read: > > > > "For a second zero on the HF side try an inductor 'in series with' the > 'zero' capacitor. The trouble is that it will have to have the same > reactance as this 1.5p capacitor and that may not be easily realisable in > practice. The inductor could also go between resonators 1 and 3 or 3 and 5 > I think. If the inductor value is too high you can use a small 'link' coil > on each of the resonators to be inductively coupled and connect these by a > pair of twisted wires. Getting the coupling right can be fiddly. You can > get another LF zero rather than the wanted HF zero, I think, if you get the > phasing wrong." . > > > > I hope this helps but as I said it is some time since I taught this stuff! > Good luck. > > > ------=_Part_10563_8708612.1177687971916 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
hi Mike -
No I don't want a zero there.  For all practical purposes I'm more than happy with what the filter actually does at the moment.
 
My puzzle is that there should be one and there isn't.  
 
An inductor coupling non-adjacent resonators appears to put a zero into the pass band;  at least it puts a huge dip there - the last thing I want.
 
Andy  G4JNT

 
On 27/04/07, Mike Underhill <mike@underhill.co.uk> wrote:

Andy

 

A correction: I should have said 'in series with' and not 'across'.  So that my post should read:

 

"For a second zero on the HF side try an inductor 'in series with' the 'zero' capacitor.  The trouble is that it will have to have the same reactance as this 1.5p capacitor and that may not be easily realisable in practice.  The inductor could also go between resonators 1 and 3 or 3 and 5 I think.  If the inductor value is too high you can use a small 'link' coil on each of the resonators to be inductively coupled and connect these by a pair of twisted wires.  Getting the coupling right can be fiddly. You can get another LF zero rather than the wanted HF zero, I think, if you get the phasing wrong."  . 

 

I hope this helps but as I said it is some time since I taught this stuff!  Good luck.

 

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