Topband: Topband ground characteristics

Tom W8JI w8ji at
Wed Oct 3 13:35:38 EDT 2012

> I have not been able to locate these FCC curves (and it appears that they
> may have been withdrawn). It would be interesting to know how the FCC 
> curves
> were derived in the first place as it assumes that someone had extensive
> area ground conductivity information.
I think the charts are not on the common FCC Internet CFR site, but are 
available by request.

As  I recall, the charts are derived from formula.

Since this is a slope and not an exact field value, it does not matter how 
the measurement device is calibrated so long as it is:

1.) Linearly marked for response over the measurement level range

2.) Stable in sensitivity over the measurement time

What I have done in the past here was build a good small loop and use a 
battery powered selective level meter, a Serria 303B.

Then, no matter what changes at a distant source or local calibration, all 
we need do is measure slope.

This does not seem that major, although it does require unchanged 
measurement points and open areas. It would NOT work for local site 
conductivity, but it would work for proofing the idea we can measure the 
very surface and conclude what happens at depth.

73 Tom 

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