X-GM-THRID: 1235384865678835942 X-Gmail-Labels: rsgb lf Delivered-To: daveyxm@gmail.com Received: by 10.35.12.7 with SMTP id p7cs40576pyi; Thu, 3 May 2007 02:03:39 -0700 (PDT) Received: by 10.66.253.17 with SMTP id a17mr1754246ugi.1178183019045; Thu, 03 May 2007 02:03:39 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id j3si2301094ugd.2007.05.03.02.03.36; Thu, 03 May 2007 02:03:39 -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) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1HjX9R-0003Hl-Ql for rs_out_1@blacksheep.org; Thu, 03 May 2007 09:59:01 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1HjX9R-0003Hc-C7 for rsgb_lf_group@blacksheep.org; Thu, 03 May 2007 09:59:01 +0100 Received: from imo-d21.mx.aol.com ([205.188.144.207]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1HjX9O-0001mm-JA for rsgb_lf_group@blacksheep.org; Thu, 03 May 2007 09:59:01 +0100 Received: from GandalfG8@aol.com by imo-d21.mx.aol.com (mail_out_v38_r9.2.) id l.cd1.dc8ce2d (42808) for ; Thu, 3 May 2007 04:58:48 -0400 (EDT) From: GandalfG8@aol.com Message-ID: Date: Thu, 3 May 2007 04:58:48 EDT To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: 9.0 SE for Windows sub 5022 X-Spam-Flag: NO X-Spam-Score: 0.6 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,NO_REAL_NAME=0.55 Subject: Re: LF: Re: Re: Passive high-pass filter circuits? Content-Type: multipart/alternative; boundary="-----------------------------1178182728" 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_20_30,HTML_MESSAGE, NO_REAL_NAME 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: 1738 -------------------------------1178182728 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 03/05/2007 02:09:27 GMT Daylight Time, weazle@hurontel.on.ca writes: If the roll off was such that the strength was around 6 dB down at 250 Hz. it would satisfy my requirements. What I'm after is reducing mains hum and its first few harmonics to a level where they are below the strength of the desired signals, which fall in the range of 1 to 4.5 kHz. ------------------------------------------ Take a look at this...... _http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=2874_ (http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=2874) As it stands, it does have quite high passband loss, around 10dB, but less stages could reduce passband loss at the expense of a less steep roll off. There should be plenty of info online allowing you to design a simple CR filter like this, it's standard textbook stuff, and there's probably sites where you can just feed in your requirements and have it churn out the results:-) If you want lower pass band losses and sharper cut off then you would probably need to consider active filters. regards Nigel GM8PZR -------------------------------1178182728 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 03/05/2007 02:09:27 GMT Daylight Time,=20 weazle@hurontel.on.ca writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>If the=20 roll off was such that the strength was around 6 dB down
at 250 Hz. it=20 would satisfy my requirements.  What I'm after is
reducing mains h= um=20 and its first few harmonics to a level where
they are below the strengt= h of=20 the desired signals, which fall in
the range of 1 to 4.5=20 kHz.
------------------------------------------
Take a look at this......
 
http://www.elecdesign.com/Articles/Index.cfm?AD=3D1&ArticleID= =3D2874
 
As it stands, it does have quite high passband loss, around 10dB, but l= ess=20 stages could reduce passband loss at the expense of a less steep roll off.
 
There should be plenty of info online allowing you to design a simple C= R=20 filter like this, it's standard textbook stuff, and there's probably sites w= here=20 you can just feed in your requirements and have it churn out the=20 results:-)
 
If you want lower pass band losses and sharper cut off then you wo= uld=20 probably need to consider active filters.
 
regards
 
Nigel
GM8PZR
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