Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

LF: Earth mode ranges

To: [email protected], Chris Osborn <[email protected]>, James Cowburn <[email protected]>, G6ALB <[email protected]>
Subject: LF: Earth mode ranges
From: Roger Lapthorn <[email protected]>
Date: Fri, 10 Dec 2010 20:12:49 +0000
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:date:message-id :subject:from:to:content-type; bh=JMwP7H/8A8AfwRkD8tV8LnmxX0jNoKVlvP77I6uFLeo=; b=weZLZZ0zgNfpOWk+8J8H06ztMLRsoS34nEUQ5eMnCH5CbE7b5644a+2QQaGeBoGRDc D1sl6xu8HyXsD3Qs3aXpCIa4+ZVZ8AXrQq3tmIFBVQ04edC5nh3smkppk7QkgWMDRpT0 zlHI84hJQSA9Rd445GkvaK/pm1TlQhGtrDcvQ=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=VgGzKG43LLR1k+u32VxMtsyTytp+kboIwpjt7ddO/G5REhi6zMskINujY5OZjlOBrE swVRCrf6Cjbhh9Q2BnxRI1aUJOmzqp/pxHOyKqXEF5yL5dtblCrwKnhftxvw698Zeehy G7s+G02igMenHwarqvgPUGGMY2Le8jZM1zUcw=
Domainkey-status: good (testing)
Reply-to: [email protected]
Sender: [email protected]
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
G3XBM   GQRP 1678    ISWL G11088
<Prev in Thread] Current Thread [Next in Thread>