Return-Path: Received: from mtain-mp03.r1000.mx.aol.com (mtain-mp03.r1000.mx.aol.com [172.29.193.71]) by air-md02.mail.aol.com (v129.4) with ESMTP id MAILINMD021-8b784d9e05eb3cc; Thu, 07 Apr 2011 14:43:55 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mp03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 4876F380000EA; Thu, 7 Apr 2011 14:43:46 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q7u9S-0005xx-16 for rs_out_1@blacksheep.org; Thu, 07 Apr 2011 19:41:54 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q7u9R-0005xo-Ic for rsgb_lf_group@blacksheep.org; Thu, 07 Apr 2011 19:41:53 +0100 Received: from mail-ww0-f41.google.com ([74.125.82.41]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q7u9O-0006DU-VC for rsgb_lf_group@blacksheep.org; Thu, 07 Apr 2011 19:41:53 +0100 Received: by wwi18 with SMTP id 18so5576360wwi.4 for ; Thu, 07 Apr 2011 11:41:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=GSetKX3T4D+qqaDiSCdwDuBgdIG2B/+XGwHjcWgRtsE=; b=G4urZiz+AU7VqUlfdFFliKkRq1XIgwxWBprt+2ZZP8htdzCBW01CuU1q/hhP8yHQPi Zmwgtc9OIbG/fLeC+559h6eKDL0ihbFr41o0t4T1OwSR4l/cERItq8gOZI/HKHDrdKHj M96j/E/DyO0CIi0oJj4V/v26xSGGD6NAu/3iE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=T+4tghG+kxVqpcZAPwjd1BZa6Vg32g7q9sUlz4Yy8NNWYp1j8n7GOOOHMumroNOl2V +0HvTCzkwa8KpB0brmS0LP/IgPQ/uyL/37cYNSlBI3V8wkcQFcjNl9rUuD1NtLcyjVi5 GhwDNGjD9iwUQkywXqsGE2XsMoQQp24QqY/qE= MIME-Version: 1.0 Received: by 10.227.150.207 with SMTP id z15mr1288189wbv.149.1302201700754; Thu, 07 Apr 2011 11:41:40 -0700 (PDT) Received: by 10.216.37.200 with HTTP; Thu, 7 Apr 2011 11:41:40 -0700 (PDT) In-Reply-To: <695A83CA124D4749BE18FDA582116731@JimPC> References: <4D9DE551.9020508@talktalk.net> <695A83CA124D4749BE18FDA582116731@JimPC> Date: Thu, 7 Apr 2011 19:41:40 +0100 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: VLF QRM puzzle - why not the same in a split screen on SL? Content-Type: multipart/alternative; boundary=0016e6ddab61cca4da04a058752b 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=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-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d017.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1dc1474d9e05e205a6 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --0016e6ddab61cca4da04a058752b Content-Type: text/plain; charset=ISO-8859-1 Thanks for this explanation Jim. People on this list are so helpful. 73s Roger G3XBM On 7 April 2011 19:33, James Moritz wrote: > Dear Roger, LF Group, > > These vertical stripes are indeed due to harmonics of the mains frequency, > specifically the 179th harmonic at nominally 8950Hz. If you watch these > harmonics with, say, "QRSS3" spectrogram settings, you will see wandering > "carriers" at multiples of 50Hz, that drift around in a range of a few 10s > of Hz near 9kHz, and may change frequency at a rate of several Hz per > minute. However, with a millihertz-resolution spectrogram, this drift rate > is fast enough that some energy appears in most of the displayed FFT bins on > the screen during one FFT window period, then drifts completely out of the > displayed range. Hence the result is a vertical streak of noise. 8970Hz/179 > is apparently close to the limit of how far the mains frequency is allowed > to drift; I usually see these bands of noise a few times a day around > 8970Hz, but it rarely reaches 8976Hz > > Cheers, Jim Moritz > 73 de M0BMU > > -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm https://sites.google.com/site/sub9khz/ --0016e6ddab61cca4da04a058752b Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Thanks for this explanation Jim.

People on this list are so helpful= .

73s
Roger G3XBM

On 7 April= 2011 19:33, James Moritz <james.moritz@btopenworld.com> wrote:
Dear Roger, LF Group,

These vertical stripes are indeed due to harmonics of the mains frequency,= specifically the 179th harmonic at nominally 8950Hz. If you watch these= harmonics with, say, "QRSS3" spectrogram settings, you will see= wandering "carriers" at multiples of 50Hz, that drift around in= a range of a few 10s of Hz near 9kHz, and may change frequency at a rate= of several Hz per minute. However, with a millihertz-resolution spectrogr= am, this drift rate is fast enough that some energy appears in most of the= displayed FFT bins on the screen during one FFT window period, then drift= s completely out of the displayed range. Hence the result is a vertical st= reak of noise. 8970Hz/179 is apparently close to the limit of how far the= mains frequency is allowed to drift; I usually see these bands of noise= a few times a day around 8970Hz, but it rarely reaches 8976Hz

Cheers, Jim Moritz
73 de M0BMU




--
http://g3xbm-qrp.blogspot.com/<= br>http://www.g3xbm.c= o.uk
http://www= .youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
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