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Date: Fri, 10 Dec 2010 20:12:49 +0000
Message-ID: <AANLkTi=kbSX_9c7EJSrjHyXq77_0uhUhEb8UxBZOXw1v@mail.gmail.com>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org, Chris Osborn <g3xiz@yahoo.co.uk>, 
	James Cowburn <james.cowburn@virgin.net>, G6ALB <andrew@tetrode.co.uk>
DomainKey-Status: good (testing) 
Subject: LF: Earth mode ranges
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A further observation from my 8.76kHz earth mode test today: with 17dB above
the noise signals at 5.1km using QRSS3 there is plenty of (theoretical)
range still to be had with utilities assisted earth mode, even using just
5W.

Assuming 18dB loss every time distance is doubled (an inverse cubed
attenuation rate for induction/conduction - is this right?) then almost 10km
should just be possible, assuming the utilities that are aiding propagation
are still there in the ground. Going from QRSS3 to QRSS30 should give
another 8-10dB (see http://www.qsl.net/on7yd/136narro.htm#QRSS). Increase
power from 5W to 100W gains another 13dB, so QRSS30 and 100W could give a
range of some 20km by utilities assisted earth mode in favourable places
based on my limited tests so far.

So, in some locations using the utilities buried in the ground all around us
could offer some quite decent ranges with an earth electrode "antenna" at
the TX end that requires minimal matching and no large loading coils, just a
step-up transformer.

What is less clear to me is what exactly is the signal being carried along?
Water pipes (often these are plastic now), overhead mains cables, gas pipes
(usually non-metallic), phone lines, rivers even?  And what about the
propagation along a sea coast with one electrode on a buoy 100m out from the
shore?

Not radiated VLF DX, but fascinating.

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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A further observation from my 8.76kHz earth mode test today: with 17dB abo=
ve the noise=20
signals at 5.1km using QRSS3 there is plenty of (theoretical) range=20
still to be had with utilities assisted earth mode, even using just 5W.<br=
>
<br>
Assuming 18dB loss every time distance is doubled (an inverse cubed=20
attenuation rate for induction/conduction - is this right?) then almost=20
10km should just be possible, assuming the utilities that are aiding=20
propagation are still there in the ground. Going from QRSS3 to QRSS30=20
should give another 8-10dB (see<a href=3D"http://www.qsl.net/on7yd/136narr=
o.htm#QRSS"> http://www.qsl.net/on7yd/136narro.htm#QRSS</a>).
 Increase power from 5W to 100W gains another 13dB, so QRSS30 and 100W=20
could give a range of some 20km by utilities assisted earth mode in=20
favourable places based on my limited tests so far.<br>
<br>
So, in some locations using the utilities buried in the ground all=20
around us could offer some quite decent ranges with an earth electrode=20
&quot;antenna&quot; at the TX end that requires minimal matching and no la=
rge=20
loading coils, just a step-up transformer.=A0 <br><br>What is less clear=
 to me is what exactly is the signal being carried=20
along? Water pipes (often these are plastic now), overhead mains cables,
 gas pipes (usually non-metallic), phone lines, rivers even?=A0
And what about the propagation along a sea coast with one electrode on a=
 buoy 100m out from the shore?<br><br>Not radiated VLF DX, but fascinating=
.<br><br>73s<br>Roger G3XBM<br clear=3D"all"><br>-- <br><a href=3D"http://=
g3xbm-qrp.blogspot.com/" target=3D"_blank">g3xbm-qrp.blogspot.com/</a><br>
<a href=3D"http://www.g3xbm.co.uk" target=3D"_blank">www.g3xbm.co.uk</a><b=
r><a href=3D"http://www.youtube.com/user/g3xbm" target=3D"_blank">www.yout=
ube.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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