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Date: Thu, 3 Feb 2011 17:12:12 +0000
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From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: LF: Earth-mode or not earth-mode
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Thanks for feedback and questions from Rik, Chris, Mal, Stefan and others on
and off this list.

*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
notobtained 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 please!
*

May I reply on a few general points raised by some?

*What is the definition of earth-mode?*

I could not find one, but my understanding is "*communication between two
points essentially using conduction through the ground*". In the modern
world it is almost impossible to find anywhere, except remote moors, that is
not criss-crossed with buried cables and pipes. My interpretation 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 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.

*Why experiment with this form of VLF/ULF communication? *

>From my tests last year it was clear that local communication
"piggy-backing" 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.

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
   get 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?
   - 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.


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.


73s
Roger G3XBM

-- 
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
<http://vlf_grabber>G3XBM   GQRP 1678    ISWL G11088

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Thanks for feedback and questions from Rik, Chris, Mal, Stefan and others=
 on and off this list. <br><br><b>I&#39;m still waiting for someone to exp=
lain 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 conne=
ction to the pipe at each end and why best receive results are with an E-f=
ield 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 &quot;<u>communicat=
ion between two points essentially using conduction through the ground</u>=
&quot;. In the modern world it is almost impossible to find anywhere, exce=
pt remote moors, that is not criss-crossed with buried cables and pipes.=
 My interpretation of earth-mode therefore includes utilising these as a=
 means of helping a signal get from (a) to (b). Hence my term &quot;utilit=
ies assisted earth-mode&quot;. In mining and military use of earth-mode I=
 think this is also 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 propagation. <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 &quo=
t;piggy-backing&quot; on these buried utilities seemed to be possible over=
 many kilometres without the need for large and complex antenna systems th=
at are essential to get even a tiny VLF signal actually <i>radiated</i>,=
 as Ossi, Gerhard, Stefan and Chris know only too well. <br>
<br>Questions I&#39;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&#39;d welcome suggestions for fu=
rther practical tests.=A0 </font><font color=3D"#000000">A lot of the expe=
rience is directly useful in the reception of DX <i>radiated</i> VLF signa=
ls. </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" targe=
t=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=A0=A0 GQRP 1678=A0=A0=A0 ISWL G11088<br>

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