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Re: AOG antennas (was Re: LF: BODGE ANTENNAS)

To: <[email protected]>
Subject: Re: AOG antennas (was Re: LF: BODGE ANTENNAS)
From: "mal hamilton" <[email protected]>
Date: Tue, 14 Dec 2010 20:33:34 -0000
References: <007901cb9bbf$2c223810$0401a8c0@xphd97xgq27nyf> <[email protected]> <[email protected]>
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John
For your specific application short range Underground to Above ground that seems the ideal environment for Earth mode induction/propagation methods.
however others are distorting the facts by claiming to be using earth mode antennas when in fact they are using grounded loops and lossy dipoles by their own admission.
also
other factors distort the facts like enhanced propagation along a sewer pipe route, gas mains, water mains pipes and ancient burial grounds, bone density etc
To avoid any ambiguity I use the traditional methods like the commercial operators and use an elevated antenna as high in the air as possible and insulated radials for the ground plane and avoid lossy buried ground wires.
Some years ago the buried wire earth systems were replaced by elevated radials on ground aeronautical DF and ground/air MF/HF installitions.
de g3kev
 
----- Original Message -----
Sent: Tuesday, December 14, 2010 7:49 PM
Subject: AOG antennas (was Re: LF: BODGE ANTENNAS)

On 14 Dec 2010, at 20:10CET, Roger Lapthorn wrote:

Mal,

Please, I make no magical claims for the earth electrode antenna I use. All I say is that, in certain circumstances, it works rather better than one might expect both on RX and TX on VLF/LF/MF.

For cave-to-surface communications we have found that, in general, an earth electrode system is much better than a tuned loop.   When we tried both systems at Kingsdale Master Cave  Valley Entrance (a standard CREG test site) the earth current antenna gave a 32 dB greater signal at the surface than did the loop.

It all seems to depend on the geology.  If the top layer of the overburden is essentially organic, then the loop tends to give better results.

We still do not have a theoretical explanation for all this, but it works.

John F5VLF

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