From: "Ford Peterson" <ford@cmgate.com>
To: <topband@contesting.com>
Date sent: Wed, 5 Mar 2003 00:52:10 -0600
Subject: Topband: Apparent ground
> I have a question about the "quality" of the ground around my station. I
> have also been pondering an interesting experiment but am only interested in
> attempting it if the results would provide meaningful results.
>
> I believe I have very good ground--rich black loam to about 3-5 ft deep,
> floating on very clay-like material, resting on crushed gravel and a water
> "table" about 30-40 ft deep.
>
> If I had a 1 foot diameter hole, down to the water table, and dropped a
> broadcast band receiver down that hole, how deep would I have to drop that
> receiver before I could no longer hear a local 50KW AM broadcast station at
> 1600KHz? Would this observation provide any indication as to the "depth" or
> "quality" of that particular ground structure on 160M?
>
> No, I have no intention of digging such a hole. ($3000 for the first 30'
> and $10 a foot thereafter) But I know a local well contractor that may
> allow me to drop a receiver down a shaft these guys dig in ground, similar
> to mine, on a weekly basis. My question is, what would it tell me about the
> nature of ground nearby? My thinking is, the results could provide an
> indication of the "apparent depth of ground" in similar soil structures.
>
> Has anybody pondered or conducted such an experiment?
>
> Ford-N0FP
> ford@cmgate.com
>
Hi, Ford-
I know little about the MF ground shielding aspects of the
experiment, but would suggest that to implement it properly,
you would want to avoid any metallic conductors going down
the hole, as they might pick up 1600KHz and conduct it right
down to the radio. In order to run a 'clean' experiment, you
would want to use perhaps an optical link up to the
surface, or else perhaps do a conversion to VHF radio
etc. and receive the recovered audio, if any, converted
up there in the spectrum. 73, David K3KY
P.S. Another uncontrolled variable- if the radio runs off of
a ferrite loopstick, how do you guard against accidentally
orienting that antenna such that the 50KW guy is right in
the antenna null?
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