Return-Path: Received: from rly-de11.mx.aol.com (rly-de11.mail.aol.com [172.19.170.147]) by air-de08.mail.aol.com (v123.4) with ESMTP id MAILINDE082-5174a1463661d2; Wed, 20 May 2009 16:09:23 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-de11.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDE118-5174a1463661d2; Wed, 20 May 2009 16:09:13 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M6s56-0005Iw-IL for rs_out_1@blacksheep.org; Wed, 20 May 2009 21:08:04 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M6s56-0005In-1i for rsgb_lf_group@blacksheep.org; Wed, 20 May 2009 21:08:04 +0100 Received: from fk-out-0910.google.com ([209.85.128.191]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M6s52-0003Wq-Ef for rsgb_lf_group@blacksheep.org; Wed, 20 May 2009 21:08:03 +0100 Received: by fk-out-0910.google.com with SMTP id k31so325120fkk.4 for ; Wed, 20 May 2009 13:07:57 -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=QkfShf8ACkURJle38odFCUJVqhmhHyL+lCKYX5euyG4=; b=yAxWwNP8HQIM9vonKoHvc2qYFvW1PIC8kzxxjcIyBNYMjQTUhMKcnBa8Wk2ZPvzAq6 k6FRuZEVJox1m8vPf3cI2OUl3kYiPkt3KxQtTHbH/wS+966xveetyFVbx9iEeYddTj1k uQETGtYxOI/mcmdnFMiTcNUUidi2NNA64z0ok= 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=sIhWjc8pEheU+MNERVtWlLCeyYqFx+29t40sBrjEhWjEeZw8kqzDvCgbb+f0qvlZ5w 8OF9aw5m8KLbqwau9cWBq4Z5vYYiZgZhOvgS2YuqAkNNtcQAlJ30YIPVxAm3H5qEjS8I h93PrvGvYXg05e+ryujN59QLnKKBDkl+pIkY8= MIME-Version: 1.0 Received: by 10.204.55.15 with SMTP id s15mr1603665bkg.53.1242850077398; Wed, 20 May 2009 13:07:57 -0700 (PDT) In-Reply-To: <117598D055BB4752B434D00FED548617@lindavideo> References: <003001c9d8c4$719e7710$6401a8c0@asus> <20090519232905.l4n0cl7o5vk0oogs@webmail4.kuleuven.be> <117598D055BB4752B434D00FED548617@lindavideo> Date: Wed, 20 May 2009 21:07:57 +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=001636c5990b5f5843046a5d9553 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,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-d252.2 ; domain : googlemail.com DKIM : pass X-Mailer: Unknown (No Version) --001636c5990b5f5843046a5d9553 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Answers to all comments. It was modelled with lossless components. I didn't have to time to do any mofre than a basic cesign.. But its a relativlely benign filter so inductors with Qu of 40 pluss should be OK. Ansoft Designer is downloadable from Ansoft http://www.ansoft.com/ansoftdesignersv/ You need to register, but teh student version is free. Its BIG ! Andy G4JNT wobbleU cubed .g4jnt.kom 2009/5/20 Ken > Hi Andy. > Where can I obtain a copy of Ansoft Designer from, I usually use Addie for > filters, a second option would be worth having. > > 73 > Ken > > M0KHW > > ----- Original Message ----- > *From:* Andy Talbot > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Tuesday, May 19, 2009 11:07 PM > *Subject:* Re: LF: 518khz - Notch Filter. > > 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. >>> >>> >>> >>> >>> >> >> >> > --001636c5990b5f5843046a5d9553 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Answers to all comments.
=A0
It was modelled with lossless components.=A0 I didn't have to time=20= to do any mofre than a basic cesign..=A0=A0 But its a relativlely benign fil= ter so inductors with Qu of 40 pluss should be OK.
=A0
Ansoft Designer is downloadable from Ansoft=A0 http://www.ansoft.com/ansoftdesignersv/=A0 Y= ou need to register, but teh student version is free.=A0=A0=A0
=A0
Its BIG !
=A0
=A0

Andy =A0G4JNT
wobbleU cubed .g4jnt.kom


=
2009/5/20 Ken <ken.h.wright@btinternet.com>=
Hi Andy.
Where can I obtain a copy of Ansoft Des= igner from, I usually use Addie for filters, a second option would be worth=20= having.
=A0
73
Ken
=A0
M0KHW=A0
----- Original Message -----
Sent: Tuesday, May 19, 2009 11:07 PM<= /div>
Subject: Re: LF: 518khz - Notch Filte= r.

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.









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