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From: Roger Lapthorn <rogerlapthorn@gmail.com>
In-Reply-To: <1292031730.7870.14.camel@vaio3rd>
Message-Id: <74719884-7F8A-4D69-BA13-80D7FC4BC223@gmail.com>
Date: Sat, 11 Dec 2010 07:55:43 +0000
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Subject: Re: LF: Earth mode ranges
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Rick

My proposed experiment would be one electrode in the sea and one 100m or=
 so in from the shore on land. I expect good range is achievable along the=
 coast to a similar station using another pair of earth electrodes in a si=
milar orientation.=20

73s
Roger G3XBM

Sent from my iPod Touch 4g

On 11 Dec 2010, at 01:42, Rick Wakatori <7l1rll@dp.u-netsurf.ne.jp> wrote:

> Hi Roger,
> Try more.
> The following grabber site has used the two electrodes earth antenna
> and good receiving QRSS/DFCW at 136kHz.
> http://www16.ocn.ne.jp/~macoco/grabber.html
> Depending on the circumstance the two electrodes earth antenna detects
> E-field between two electrodes. If this assumption is correct, lake side
> or shore side including on the sea using buoy make two electrodes short
> condition.
>  We will try to do experiment at 2200m band.
> 73
> Rick - 7L1RLL
>=20
> On Fri, 2010-12-10 at 20:12 +0000, Roger Lapthorn wrote:
>> 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.
>>=20
>> 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.
>>=20
>> 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. =20
>>=20
>> 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?
>>=20
>> Not radiated VLF DX, but fascinating.
>>=20
>> 73s
>> Roger G3XBM
>>=20
>> --=20
>> g3xbm-qrp.blogspot.com/
>> www.g3xbm.co.uk
>> www.youtube.com/user/g3xbm
>> G3XBM   GQRP 1678    ISWL G11088
>=20
>=20