[TowerTalk] TowerTalk Digest, Vol 158, Issue 20

[jimlux]

On 2/9/16 9:41 AM, Donald Chester wrote:
>> Also there is an averaging area dimension for the map - I don't remember
>> what it is - but any given soil in an area of less than that size,  can vary
>> quite a bit from the map values.
>
>> 73 John N5CQ
>
> Exactly.  Look at the map. Some adjacent sections jump abruptly from the lowest conductivity to the highest.
> Santa Fe, N Mexico is a good example, where it's 15 on one side of the line, and just to the north across
> the boundary, it's only 2. See section 15w.jpg on the FCC map.
>
> You know the actual contours would rarely, if ever, precisely follow the boundaries shown on the map,
> jumping abruptly from low conductivity at one point, to high conductivity just a few feet to the other side of the
> line.  Those maps, based on random samples, are virtually useless for predicting the soil conductivity at any
> specific site location. They might be somewhat useful as a preliminary guideline, but no substitute for actual
> measurement.


It's useful for deciding "are we building our AM transmitter in a good 
or bad conductivity location"