Some interesting reading perhaps - In a former life Ive spent hours, sometimes days wandering around neighborhoods with my DF set and SG browns tracking painful tv/radio interference issues and can vouch for the interaction!
http://www.netl.doe.gov/technologies/oil-gas/publications/td/FG113004.PDF
Laurence
Date: Wed, 23 Jun 2010 08:42:56 +0100
From: [email protected]
To: [email protected]
Subject: Re: LF: RE: VLF QRP Earth mode: 5.1km DX tonight but no such thing as a free lunch
Rik (et al),
One earth rod in the sea at each end and another driven into the chalk rock 300m inland at each end and would almost guarantee a QSO on 1kHz across the channel by earth-mode. Anyone crossing the channel would be able to detect the signal with a loop in a boat. Two rods in the sea at each end would not work.
Also, you do wonder with the network of gas pipes, water pipes, electricity pylons, phone lines etc criss-crossing vast swathes of countryside just how far "utility assisted" (for the want of a better term) earth mode VLF comms could travel. From my own QRP tests this week I conclude a LOT further than I'd previously thought possible. Of course no direct physical connection is needed, just the ability to induce power into these by placing wire loops or earth electrode loops nearby.
This raises another point. However unintentionally, 136kHz, 500kHz and 1.8MHz signals must, at times, couple into utilities and be "helped" to radiate more effectively by the presence of cables and pipes. I am now almost sure that the same mechanism used to conduct my 838Hz signal a very long way last night must have helped my 500kHz WSPR signal cross the UK last weekend: there is a signal flowing in the earth electrode "loop in the ground" as well as a signal flowing around the streets via copper water pipes. Whether the mechanism at 500kHz or 137kHz is as a result of a loop or a very long e-field antenna (the copper pipes in the streets) just below the surface of the earth is open to debate.
Fascinating.
73s
Roger G3XBM
On 23 June 2010 08:15, Rik Strobbe <[email protected]> wrote:
Yet another thought:
salt water is a rather good conductor.
What about a couple of rods into the sea near Dover and another pair near Cap Griz Nez ?
Distance is 34 km.
73, Rik ON7YD
- At greater distances (3-5kms) the signal reaches its destination by conduction through the ground aided by pipes in the roads and with inductive coupling into the loop at the RX.
Roger,
very interesting.
There are huge gas pipelines running across the country (and even across Europe).
I wonder how far one would get with a ground antenna near one of these.
The 2 rods of the ground antenna each at one side of the pipeline would give optimal coupling.
73, Rik ON7YD
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