From: John Rabson <john.rabson@numeo.fr>
Mime-Version: 1.0 (Apple Message framework v1082)
Date: Thu, 3 Feb 2011 19:36:12 +0100
In-Reply-To: <AANLkTik25SxY1Uo0BLO5wCPPak_xr4ZnQzp4CbDqkAON@mail.gmail.com>
To: rsgb_lf_group@blacksheep.org
References: <AANLkTik25SxY1Uo0BLO5wCPPak_xr4ZnQzp4CbDqkAON@mail.gmail.com>
Message-Id: <6156A530-183D-4560-9CC1-3F2EE72300EC@numeo.fr>
Content-Type: multipart/alternative; boundary=Apple-Mail-23-623393048
Subject: Re: LF: Earth-mode or not earth-mode
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


--Apple-Mail-23-623393048
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
	charset=us-ascii

Roger,

Yes, this is the place to tell people about VLF work.  Although the title=
 of the reflector refers to LF, there is a lot of traffic about 500 kHz,=
 and other frequencies when relevant.

As these involved in caving and tunnel communications know well, this part=
 of the spectrum has many uses - it is not necessarily a question of how=
 many countries you can work.

73
John F5VLF

On 3 Feb 2011, at 18:12CET, Roger Lapthorn wrote:

> Thanks for feedback and questions from Rik, Chris, Mal, Stefan and other=
s on and off this list.=20
>=20
> I'm still waiting for someone to explain to me why, if this is (mainly)=
 conduction along metal pipes, which I am sure it is, best results are not=
 obtained with a galvanic connection to the pipe at each end and why best=
 receive results are with an E-field probe. I remain puzzled. Answers plea=
se!
>=20
> May I reply on a few general points raised by some?
>=20
> What is the definition of earth-mode?
>=20
> I could not find one, but my understanding is "communication between two=
 points essentially using conduction through the ground". In the modern wo=
rld it is almost impossible to find anywhere, except remote moors, that is=
 not criss-crossed with buried cables and pipes. My interpretation of eart=
h-mode therefore includes utilising these as a means of helping a signal=
 get from (a) to (b). Hence my term "utilities assisted earth-mode". In mi=
ning and military use of earth-mode I think this is also accepted. What I=
 also mean is communicating from (a) to (b) not using a radiated signal or=
 induction as the prime means of propagation.=20
>=20
> Why experiment with this form of VLF/ULF communication?=20
>=20
> From my tests last year it was clear that local communication "piggy-bac=
king" on these buried utilities seemed to be possible over many kilometres=
 without the need for large and complex antenna systems that are essential=
 to get even a tiny VLF signal actually radiated, as Ossi, Gerhard, Stefan=
 and Chris know only too well.=20
>=20
> Questions I'm trying to answer are:
> How best to launch a signal?
> What in the ground (apart from water, soil and rock) helps the signal ge=
t from (a) to (b)?
> What works best to pick up the VLF/ULF signal at the far end of the link=
?
> What frequencies work best?
> What are the noise sources and how can these be minimised?
> How close to buried utilities does one really have to be for it to work?
> Can one use rivers, canals or the sea coast for earth-mode?=20
> How little/much power is needed for a given range?
> What modes are most effective?
> What is the practical range limit?
> Is there a practical use for this form of communication?
> Also, I'd welcome suggestions for further practical tests.  A lot of the=
 experience is directly useful in the reception of DX radiated VLF signals=
.=20
>=20
> Results have been shared here because others are known to be interested=
 in this aspect of VLF work, but if people think the LF-reflector is not=
 the right place please say so.=20
>=20
>=20
> 73s
> Roger G3XBM
>=20
> --=20
> g3xbm-qrp.blogspot.com/
> www.g3xbm.co.uk
> www.youtube.com/user/g3xbm
> G3XBM   GQRP 1678    ISWL G11088

--Apple-Mail-23-623393048
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html;
	charset=us-ascii

<html><head></head><body style=3D"word-wrap: break-word; -webkit-nbsp-mode=
: space; -webkit-line-break: after-white-space; ">Roger,<div><br></div><di=
v>Yes, this is the place to tell people about VLF work. &nbsp;Although the=
 title of the reflector refers to LF, there is a lot of traffic about 500=
 kHz, and other frequencies when relevant.</div><div><br></div><div>As the=
se involved in caving and tunnel communications know well, this part of th=
e spectrum has many uses - it is not necessarily a question of how many co=
untries you can work.</div><div><br></div><div>73</div><div>John F5VLF</di=
v><div><br><div><div>On 3 Feb 2011, at 18:12CET, Roger Lapthorn wrote:</di=
v><br class=3D"Apple-interchange-newline"><blockquote type=3D"cite">Thanks=
 for feedback and questions from Rik, Chris, Mal, Stefan and others on and=
 off this list. <br><br><b>I'm still waiting for someone to explain to me=
 why, if this is (mainly) conduction along metal pipes, which I am sure it=
 is, best results are <i>not</i> obtained with a galvanic connection to th=
e pipe at each end and why best receive results are with an E-field probe.=
 I remain puzzled. Answers please!</b><br>
<br>May I reply on a few general points raised by some?<br><br><div style=
=3D"margin-left: 40px;"><u><b>What is the definition of earth-mode?</b></u=
><br><br>I could not find one, but my understanding is "<u>communication=
 between two points essentially using conduction through the ground</u>".=
 In the modern world it is almost impossible to find anywhere, except remo=
te moors, that is not criss-crossed with buried cables and pipes. My inter=
pretation of earth-mode therefore includes utilising these as a means of=
 helping a signal get from (a) to (b). Hence my term "utilities assisted=
 earth-mode". In mining and military use of earth-mode I think this is als=
o accepted. What I also mean is communicating from (a) to (b) <i>not</i>=
 using a radiated signal or induction as the <i>prime</i> means of propaga=
tion. <br>
<br><u><b>Why experiment with this form of VLF/ULF communication? </b></u>=
<br><br>From my tests last year it was clear that local communication "pig=
gy-backing" on these buried utilities seemed to be possible over many kilo=
metres without the need for large and complex antenna systems that are ess=
ential to get even a tiny VLF signal actually <i>radiated</i>, as Ossi, Ge=
rhard, Stefan and Chris know only too well. <br>
<br>Questions I'm trying to answer are:<br></div>=20

<ul style=3D"margin-left: 40px;"><li>How best to launch a signal?</li>
<li>What in the ground (apart from water, soil and rock) helps the signal=
 get from (a) to (b)?</li><li>What works best to pick up the VLF/ULF signa=
l at the far end of the link?</li><li>What frequencies work best?</li><li>
What are the noise sources and how can these be minimised?<br></li><li>How=
 close to buried utilities does one really have to be for it to work? </li=
>
<li>Can one use rivers, canals or the sea coast for earth-mode? <br></li><=
li>How little/much power is needed for a given range?</li><li>What modes=
 are most effective?</li><li>What is the practical range limit?</li><li>Is=
 there a practical use for this form of communication?<br>
</li></ul><font color=3D"#000000">Also, I'd welcome suggestions for furthe=
r practical tests.&nbsp; </font><font color=3D"#000000">A lot of the exper=
ience is directly useful in the reception of DX <i>radiated</i> VLF signal=
s. </font><font color=3D"#000000"><br>
<br>Results have been shared here because others are known to be intereste=
d in this aspect of VLF work, but if people think the LF-reflector is <i>n=
ot</i> the right place please say so. <br><br>
<br>73s<br>Roger G3XBM<br><br></font><span style=3D"color: rgb(255, 0, 0);=
"></span>-- <br><a href=3D"http://g3xbm-qrp.blogspot.com/" target=3D"_blan=
k">g3xbm-qrp.blogspot.com/</a><br><a href=3D"http://www.g3xbm.co.uk/" targ=
et=3D"_blank">www.g3xbm.co.uk</a><br>

<a href=3D"http://www.youtube.com/user/g3xbm" target=3D"_blank">www.youtub=
e.com/user/g3xbm</a><br><a href=3D"http://vlf_grabber/" target=3D"_blank">=
</a>G3XBM&nbsp;&nbsp; GQRP 1678&nbsp;&nbsp;&nbsp; ISWL G11088<br>
</blockquote></div><br></div></body></html>=3D

--Apple-Mail-23-623393048--