Topband: Apparent ground

Tom Rauch w8ji at
Thu Mar 6 05:59:17 EST 2003

> I wonder about the value of knowing the "Apparent Depth of Ground?"
> Comments on this reflector suggest that if an antenna ground plane is
> more than a few inches below the surface it would be irrelevant so far
> as antenna performance is concerned.  Losses in the top layer of soil
> would make it inaccessible to the currents flowing in the
> antenna-counterpoise system.

That is an overstatement of what actually occurs. Even a deep ground (say a
foot or two deep) helps, it's just that closer to the surface is better. The
skin depth on 160 is several feet to perhaps 50 feet.

The radio test would not tell you anything except a combination of how
sensitive the radio was and how much attenuation there was.

Both noise and signal would fall at the same gradually increased attenuation
with increased depth. This is the same problem in submarine communications.
The signal is there, it becomes weaker in exactly the same proportion as
external noise until eventually S/N is limited by internal receiver noise.

73 Tom

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