Return-Path: Received: from mtain-db11.r1000.mx.aol.com (mtain-db11.r1000.mx.aol.com [172.29.64.95]) by air-dc02.mail.aol.com (v129.4) with ESMTP id MAILINDC022-86264c2ba62be6; Wed, 30 Jun 2010 16:16:43 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-db11.r1000.mx.aol.com (Internet Inbound) with ESMTP id 1733B3800007D; Wed, 30 Jun 2010 16:16:41 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OU3gm-0000bp-RF for rs_out_1@blacksheep.org; Wed, 30 Jun 2010 21:15:20 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OU3gm-0000bg-6d for rsgb_lf_group@blacksheep.org; Wed, 30 Jun 2010 21:15:20 +0100 Received: from mail-ww0-f49.google.com ([74.125.82.49]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OU3gl-0000vJ-B2 for rsgb_lf_group@blacksheep.org; Wed, 30 Jun 2010 21:15:20 +0100 Received: by wwi14 with SMTP id 14so135815wwi.18 for ; Wed, 30 Jun 2010 13:15:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:content-type; bh=ymsxZeX0Z+KF5TuTWxBJqzZ2ez2s99G8u6g9Hu6SXmw=; b=IDo3je8bFIkMlvNEvXH4qNkacDnEA0V1Du7uIWAwIVjWl0K1HNWzX3AvpOFvlq63OP MkO+MbTs7wk/MzZc8Pci9nZxoiyWdn+ugK9XIRl/eNZjzjI9la6H5PQwiRzNWMoYSy6j p2rt+VYmEa3BrotQC9SSkmMp95HVEvH11orPU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=JVjWF0lIzb+2Bp+sxVTu3o7lFfq+na/sQKk4bhijzB7jOoZ6b9WJCKqs9I087iKqdp 1bQYCLdsrYgNAJmyZZoUY9wJHChKnxJLGGfNgcvhyAHjjnw7uLKpns0ePLp36eh24pOZ BaXgkqTI2ZlNVzZd7EuKyteY+62ShgCQ2vNHE= MIME-Version: 1.0 Received: by 10.216.89.140 with SMTP id c12mr74217wef.78.1277928911319; Wed, 30 Jun 2010 13:15:11 -0700 (PDT) Received: by 10.216.175.12 with HTTP; Wed, 30 Jun 2010 13:15:11 -0700 (PDT) In-Reply-To: <004101cb188b$c3c576d0$0202a8c0@laptopcore2> References: <3678DF146BA54B2FA2E4F9A0D743F517@JohnPC> <004101cb188b$c3c576d0$0202a8c0@laptopcore2> Date: Wed, 30 Jun 2010 21:15:11 +0100 X-Google-Sender-Auth: WxUo5-hdmseEyqeJnCpuufD0GUs Message-ID: From: Gary - G4WGT To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,HTML_TAG_EXIST_TBODY=0.126 Subject: Re: LF: RE: Re: RE: Gas pipe Content-Type: multipart/alternative; boundary=0016e6d78475ceb38d048a450274 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, HTML_TAG_EXISTS_TBODY 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-d221.2 ; domain : gmail.com DKIM : fail x-aol-sid: 3039ac1d405f4c2ba6293a73 X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --0016e6d78475ceb38d048a450274 Content-Type: text/plain; charset=ISO-8859-1 Hi Edie & John, I found this mail in my bin from Jim M0BMU on the subject, could this be the one. Copy below. Gary - G4WGT. ****************************** Dear LF Group, On the subject of VLF signal propagation along buried conductors, and its use by cable locators, I thought it would be interesting to try one out, so I borrowed one (see attached picture)... The CAT detector part is a passive magnetic field sensor. It has an audible output and operates in 3 modes. "Power" mode detects 50Hz and harmonics from power cables, and also any other conductor that has some 50Hz common-mode current flowing in it, which is most conductors in practice! In "Radio" mode, it is a simple direct conversion VLF receiver with zero beat around 17.8kHz and bandwidth of a few kilohertz. This detects currents induced by signals from VLF utilities - it is quite sensitive, if you turn the gain control up you can hear several MSK signals and the background QRN too. I found the results rather ambiguous, since it is hard to decide if you are picking up a signal from a cable, or just the normal radiated signal. The "Generator" mode uses the seperate "Genny" unit to inject a signal into the cable you want to trace. It generates an on-off keyed CW signal at 32.768kHz; apparently the output current is 100mA. When the detector is switched to Generator mode, it acts as a 32.768kHz receiver with a bandwidth of a few hundred Hz, so you can hear the "beeps" from the generator. It is also quite sensitive in this mode; the literature says it can detect 5uA signal current 1m away. As a test, I connected one terminal of the generator to the mains earth in my house, and the the other terminal to some RF ground rods at the end of the garden. This gave a strong signal on the mains cable entering the house, and also apparently the gas main (which despite Mal's proclamations, stubbornly remains of a ferrous nature ;-)). It was possible to trace the various pipes and cables for hundreds of metres - the limiting factors seemed to be that as the pipes/cables branched off to other houses, street lighting, etc, the signal got weaker, presumably as an increasing portion of the signal current was diverted away from the main cable, and also some buzzing QRM appeared, which seemed to be associated with BT telecomms cables. Apparently, contractors are more or less obliged to have these detectors, so that if they accidentally dig up a pipe or a cable they can say they "took all reasonable precautions" for insurance purposes. But in use, the results certainly need to be interpreted with care - it is often unclear what is or isn't being detected. I suppose if you want to experiment with this kind of VLF transmission before an NoV is available, you could always say it wasn't radio, but a cable tracing experiment ;-) Cheers, Jim Moritz 73 de M0BMU [image: CATandGenny.jpg] *CATandGenny.jpg* 48K View Download ******************************* On 30 June 2010 20:38, g3zjo wrote: > > >Just north of here where I live there is such a line and only 5 miles > is a >pumping station and I was wondering if I would be able to receive > these >signals. This is off topic for this reflector but I was sure I > that I seen >it on one of these websites. Anyway thank you all for the > time and the >space. > > You are very welcome John. Either JNT or BMU I seem to remember borrowed > a pipe tracer and there was a write up with some colour pictures, I > can't seem to find it. > > Now why didn't say you were 'Dreaming' of hearing those signals, one > Brit will tell you you're a dreamer and wasting your time, another will > do some practical tests and a German will demonstrate that it is easy to > vastly exceed your dreams :-) > > 73 > > Eddie G3ZJO > > > --0016e6d78475ceb38d048a450274 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Edie & John,

I found this mail in my bin from Ji= m M0BMU on the subject, could this be the one. Copy below.

<= /div>
Gary - G4WGT.

*************************= *****
Dear LF Group,

On the subject of VLF signal propagation along burie= d conductors, and its use by cable locators, I thought it would be interes= ting to try one out, so I borrowed one (see attached picture)...

Th= e CAT detector part is a passive magnetic field sensor. It has an audible= output and operates in 3 modes. "Power" mode detects 50Hz and= harmonics from power cables, and also any other conductor that has some= 50Hz common-mode current flowing in it, which is most conductors in pract= ice! In "Radio" mode, it is a simple direct conversion VLF recei= ver with zero beat around 17.8kHz and bandwidth of a few kilohertz. This= detects currents induced by signals from VLF utilities - it is quite sens= itive, if you turn the gain control up you can hear several MSK signals an= d the background QRN too. I found the results rather ambiguous, since it= is hard to decide if you are picking up a signal from a cable, or just th= e normal radiated signal.

The "Generator" mode uses the seperate "Genny" uni= t to inject a signal into the cable you want to trace. It generates an on-= off keyed CW signal at 32.768kHz; apparently the output current is 100mA.= When the detector is switched to Generator mode, it acts as a 32.768kHz= receiver with a bandwidth of a few hundred Hz, so you can hear the "= beeps" from the generator. It is also quite sensitive in this mode;= the literature says it can detect 5uA signal current 1m away.

As a test, I connected one terminal of the generator to the mains eart= h in my house, and the the other terminal to some RF ground rods at the en= d of the garden. This gave a strong signal on the mains cable entering the= house, and also apparently the=A0gas=A0main (which despite Mal's proclamations, stubbornly remains of= a ferrous nature ;-)). It was possible to trace the various pipes and cab= les for hundreds of metres - the limiting factors seemed to be that as the= pipes/cables branched off to other houses, street lighting, etc, the sign= al got weaker, presumably as an increasing portion of the signal current= was diverted away from the main cable, and also some buzzing QRM appeared= , which seemed to be associated with BT telecomms cables.

Apparently, contractors are more or less obliged to have these detecto= rs, so that if they accidentally dig up a pipe or a cable they can say the= y "took all reasonable precautions" for insurance purposes. But= in use, the results certainly need to be interpreted with care - it is of= ten unclear what is or isn't being detected. I suppose if you want to= experiment with this kind of VLF transmission before an NoV is available,= you could always say it wasn't radio, but a cable tracing experiment= ;-)

Cheers, Jim Moritz
73 de=A0M0BMU

3D"CATandGe= CATandGenny.jpg
4= 8K=A0=A0=A0View=A0=A0=A0Down= load=A0=A0

*******************************<= /div>

On 30 June 2010 20:38, g3zjo <g3zjo@npton.plus.com> wro= te:

>Just north of here where I live there is such a line and only 5 miles<= br> is a >pumping station and I was wondering if I would be able to receive=
these >signals. This is off topic for this reflector but I was sure I that I seen >it on one of these websites. Anyway thank you all for the<= br> time and the >space.

You are very welcome John. Either JNT or BMU I seem to remember borrowed a pipe tracer and there was a write up with some colour pictures, I
can't seem to find it.

Now why didn't say you were 'Dreaming' of hearing those signal= s, one
Brit will tell you you're a dreamer and wasting your time, another wil= l
do some practical tests and a German will demonstrate that it is easy to vastly exceed your dreams :-)

73

Eddie G3ZJO



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