W4RNL also points out how much poorer our soils generally are than we think
they are. We also have to be careful because a lot of his data is unverified
except through models which are also not verified.
The trend is, as we would expect, very good soils require smaller ground
systems. This is especially true with halfwave or "ground independent"
radiators, and less true with antennas with little height above ground. The
shorter the vertical antenna or closer to ground the horizontal antenna, the
more any given system requires a significant ground system.
Early on, Amateur Radio books used to describe a method of measuring soil
that gave totally misleading results using soil surface resistance probes to
measure resistance because it ignored the fact the media (soil) almost
always isn't even remotely close to being uniform.
We also have to be very careful with models, because the soil we have around
an antenna is virtually never homogeneous, and almost always not even
remotely close to homogeneous. It is a widely varying mix of moisture as
well as soil types.
Because of this, any model that treats the earth as a uniform media will not
be "accurate", even if we consider accurate + - 50% as "accurate".
While the idea that better soil makes better field strength is certainly
correct in any given case, I think it would be much more factual if we
reserved words like "accurate" for things that are proven with actual
verifying measurements, and not assumed.
I've seen far to many things that are initially thought to be verified or
accurate turn out to be not so accurate in a few years. Let's not confuse
trends with absolutes.
73 Tom
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