Return-Path: Received: from mtain-mh05.r1000.mx.aol.com (mtain-mh05.r1000.mx.aol.com [172.29.96.217]) by air-db09.mail.aol.com (v129.4) with ESMTP id MAILINDB091-85f54d9dea9f2d9; Thu, 07 Apr 2011 12:47:27 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mh05.r1000.mx.aol.com (Internet Inbound) with ESMTP id A0A8C38000114; Thu, 7 Apr 2011 12:47:24 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q7sLC-0004XX-3w for rs_out_1@blacksheep.org; Thu, 07 Apr 2011 17:45:54 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q7sLB-0004XO-OD for rsgb_lf_group@blacksheep.org; Thu, 07 Apr 2011 17:45:53 +0100 Received: from mhost02c.leeds.ac.uk ([129.11.76.154]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q7sL9-00040G-BR for rsgb_lf_group@blacksheep.org; Thu, 07 Apr 2011 17:45:53 +0100 Received: from APOLLO1.ds.leeds.ac.uk (apollo1.leeds.ac.uk [129.11.5.4]) by mhost02c.leeds.ac.uk (8.14.4/8.14.4) with ESMTP id p37Gjj1D019679 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NOT) for ; Thu, 7 Apr 2011 17:45:45 +0100 (BST) Received: from HERMES8.ds.leeds.ac.uk ([fe80::39ce:23e:d0b5:7e24]) by APOLLO1.ds.leeds.ac.uk ([129.11.5.4]) with mapi; Thu, 7 Apr 2011 17:45:45 +0100 From: Chris Trayner To: "rsgb_lf_group@blacksheep.org" Date: Thu, 7 Apr 2011 17:45:43 +0100 Thread-Topic: LF: VLF QRM puzzle - why not the same in a split screen on SL? Thread-Index: Acv1QzxxusrYBsVfS3+jfFz80aMfyg== Message-ID: References: <4D9DE551.9020508@talktalk.net> In-Reply-To: <4D9DE551.9020508@talktalk.net> Accept-Language: en-US, en-GB Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, en-GB MIME-Version: 1.0 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: VLF QRM puzzle - why not the same in a split screen on SL? Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=TO_ADDRESS_EQ_REAL 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-global-disposition: G x-aol-sid: 3039ac1d60d94d9dea982682 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : temperror X-Mailer: Unknown (No Version) On 7 Apr 2011, at 17:24, qrss wrote: > Considering they=20 > originate from a 50Hz source they are strongest at lower frequencies,=20 > rarely climbing above 6kHz but peaks sometimes get to 8.971kHz not much= =20 > higher.. Yes, but they disappear between 8970.03 Hz and 9876.57 Hz - that's a very= small band for anything to knock them out. It's 0.00105 of an octave. If= something is acting like a low-pass filter, at 6dB/octave/order, it'd hav= e to be something like a 500th order filter to drop the signal by 3dB. I agree, it does look strange.=20 73, Chris G4OKW =20 ----------------------- Dr Chris Trayner School of Electronic & Electrical Engineering, The University of Leeds, Leeds LS2 9JT, United Kingdom Tel: +44 113 34 32053 Fax: +44 113 34 32032