Return-Path: Received: from rly-de05.mx.aol.com (rly-de05.mail.aol.com [172.19.170.141]) by air-de01.mail.aol.com (v123.4) with ESMTP id MAILINDE014-4db4a132dc7370; Tue, 19 May 2009 18:08:25 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-de05.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDE058-4db4a132dc7370; Tue, 19 May 2009 18:08:09 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M6XSx-0006lS-A8 for rs_out_1@blacksheep.org; Tue, 19 May 2009 23:07:19 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M6XSw-0006lJ-P0 for rsgb_lf_group@blacksheep.org; Tue, 19 May 2009 23:07:18 +0100 Received: from mail-bw0-f171.google.com ([209.85.218.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M6XSt-00058g-9D for rsgb_lf_group@blacksheep.org; Tue, 19 May 2009 23:07:18 +0100 Received: by bwz19 with SMTP id 19so105830bwz.4 for ; Tue, 19 May 2009 15:07:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=Ek2sdLjHysjK74mj3NH39PIKMQ8k9ixKYPUM7Ok/xOM=; b=wcET4CldHrTFPPUu69+8Cx4EKj7galixzqXMEqavea2eRJlQR3o8QD/uwQysCJvQLZ WVS5mWJm0Ho3AwzTd7Ahn8lT+X1zuXDKj95Jg6kjOEjP8yIAArCykVMUuH86JfMblFi/ njsa80EqNhdVsz79e05Ed1t1mwz0ltBLZKpBQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=t23XXi1m8AYFarhMy8ia7raj2cHkv1s8mE+9m+lP9QNLJyQfSOveSha4JLGEe/+B9l eSHhwY7MZeAj7KmfH+2v+RrrmrpINYcD6sjcoEJCXwb5BmPctgHxKIyfrr9t9MQDwSWU M1ANb2ve7xTGxC7UPM/HYphehMPKg1RKV4zOo= MIME-Version: 1.0 Received: by 10.204.52.146 with SMTP id i18mr503575bkg.82.1242770828756; Tue, 19 May 2009 15:07:08 -0700 (PDT) In-Reply-To: <20090519232905.l4n0cl7o5vk0oogs@webmail4.kuleuven.be> References: <003001c9d8c4$719e7710$6401a8c0@asus> <20090519232905.l4n0cl7o5vk0oogs@webmail4.kuleuven.be> Date: Tue, 19 May 2009 23:07:08 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: 518khz - Notch Filter. Content-Type: multipart/alternative; boundary=001636c5abdfc9081c046a4b2143 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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 X-AOL-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d275.1 ; domain : googlemail.com DKIM : pass X-Mailer: Unknown (No Version) --001636c5abdfc9081c046a4b2143 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Ansoft Designer came up with this solution. http://www.g4jnt.com/518kHz_BandStop.gif The component values aren't particulalrly nice, and there is almost certainly a nicer design with transformers to be found, but... Andy G4JNT 2009/5/19 Rik Strobbe > Gary, > > a simple series L-C notch works best when > - Q is high = you need a good coil (capacitor Q shouldn't be the problem) > - the output "sees" a high impedance (FET buffer) > - the source impedance is high compared to the loss resistance of the coil > (eventualy put a R of a few 100 Ohm in serie with the antenna) > But it will be a hard job to get a decent attenuation at 518 while passing > 501-506 without too much losses. > > An alternative would be a xtal filter as a passband filter for 501-506. > If you can find a number of 500kHz xtals and "polish" them up some kHz. > > 73, Rik ON7YD - OR7T > > > Quoting Gary - G4WGT : > > Hi LF, >> >> >> >> You may have seen an image of a NAVTEX signal on my 500KHz grabber at >> about >> 506KHz. The original of this image is at 518KHz. The receiver for this >> grabber is a Softrock Lite 455KHz module modified for 500KHz. >> >> >> >> I have attempted to notch the signal using a simple series or parallel >> filter but only succeeded in seriously degrading the whole band possibly >> due >> to the bandwidth of the filter?? >> >> >> >> Is there some simple narrow notch filter which I could use to remove the >> offending signal. >> >> >> >> 73, >> >> >> >> Gary - G4WGT - IO83QP. >> >> >> >> >> > > > --001636c5abdfc9081c046a4b2143 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Ansoft Designer came up with this solution.=A0
=A0
=A0
The component values=A0aren't=A0particulalrly nice, and there is al= most certainly a nicer design with transformers to be found, but...

Andy =A0G4JNT


2009/5/19 Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>= ;
Gary,

a simple series L-C n= otch works best when
- Q is high =3D you need a good coil (capacitor Q sh= ouldn't be the problem)
- the output "sees" a high impedance (FET buffer)
- the source=20= impedance is high compared to the loss resistance of the coil (eventualy put= a R of a few 100 Ohm in serie with the antenna)
But it will be a hard jo= b to get a decent attenuation at 518 while passing 501-506 without too much=20= losses.

An alternative would be a xtal filter as a passband filter for 501-506.<= br>If you can find a number of 500kHz xtals and "polish" them up s= ome kHz.

73, Rik =A0ON7YD - OR7T=20


Quoting Gary - G4WGT <g4wgt@tiscali.co.uk>:

Hi LF,



You may have= seen an image of a NAVTEX signal on my 500KHz grabber at about
506KHz. T= he original of this image is at 518KHz. The receiver for this
grabber is a Softrock Lite 455KHz module modified for 500KHz.


I have attempted to notch the signal using a simple series or parallel
f= ilter but only succeeded in seriously degrading the whole band possibly due<= br> to the bandwidth of the filter??



Is there some simple narrow=20= notch filter which I could use to remove the
offending signal.


73,



Gary - G4WGT - IO83QP.








--001636c5abdfc9081c046a4b2143--