Topband: ground characteristics

[Jim Brown]

On 10/3/2012 12:35 AM, Bob Kupps wrote:
> "It is impossible to make a direct measurement of ground characteristics".

Horsepucky.  Now, what IS difficult is to make a direct measurement to 
great depth!  But N6LF has shown a simple method to measure to the depth 
of whatever length of rod you are willing (and able) to drive.

The "slope of the decay of field strength" method is a very good method 
for frequencies for which good data is published,  but to get good data 
you've got to take a lot of data points along a radial from the test 
transmitter site.  More than fifty years ago, I worked for a broadcast 
consultant who did that as part of his applications for new licenses in 
a band that had been full for 30 years. )  My job was to plot his data 
and extract the conductivity data.

You could, for example, use this method with a local broadcaster 
operating near the high end of the AM broadcast band. BUT -- you need 
calibrated instrumentation to get accurate field strength measurements, 
and you need to make a LOT of measurements at a chosen azimuth that 
covers the area of interest along a line drawn from the transmitter to 
and past the area of interest.  You must then plot that data of field 
strength vs. distance, then compare it to FCC curves for that operating 
frequency, matching the SLOPE of your data to one of the several 
families of curves in the FCC data.

This is NOT a trivial exercise!

73, Jim K9YC