Topband: Ground conductivity, permittivity measurement

[Tom W8JI]

Cristi,

Thank you for the thoughtful answer.

If I was of a mind to verify the use of probes, I would look at the 
attenuation slope of sample signal from a distance source across the area 
being measured and carefully record that slope. THIS DOES NOT require a 
calibrated instrument to a certain field intensity reference or a certain 
radiated power, because we are only determining the slope along a distance. 
We don't care if it is mV/m or Cris per meter, or Tom per meter. We only 
care that we measure the slope.

Then I would sample the earth with my proposed method, in this case the 
probes, and record that data.

If the two correlate over seasonal, temperature, or moisture changes, then 
it appears logical the probes have value over that particular frequency and 
soil type.

The problem with probes or buried lines is they at best only sample a very 
small cross section of earth near the surface. It is very easy to understand 
this might not correlate at all with fields that extend many meters deep. It 
is like looking at the thin skin to detect what happens deep inside. 
Obviously if the field is mostly gone past the thin skin, we only need look 
at the skin. Likewise if the field extends far beyond the skin, we are not 
measuring anything meaningful for the wave.

I think a scholarly person wanting to verify a method like this would make a 
test like this over a variety of soils, but I cannot find such verification. 
Without such a test it is a matter of blind faith that what happens in the 
first meter or less is what happens several meters down.

I would agree with your idea about multiple points making it meaningful if 
you also moved the probes deep below ground, to a depth where the field 
diminished to unimportant values. I think this is a case of not being able 
to do things right, so we dismiss what probably is a problem.

73 Tom