[600MRG] FCC maps

[Kenneth G. Gordon]

On 5 Feb 2016 at 9:34, Rudy Severns wrote:

> Thanks very much Steve for the link.

Yes. Thank you.
  
> But we need to be a bit cautious when using them.  The FCC soil conductivity
> maps are great for BC ground wave coverage analysis but they are much too coarse
> for an individual QTH.  The maps can be grossly misleading!

I had wondered about that.

> For example:  at my QTH the measured soil conductivity at 475 kHz is in the
> range 7-15 mS/m depending on the season (wet or dry).  At other places nearby
> the conductivities are even higher.  The FCC soil map for western Oregon says 4
> mS/m but this is an average of rich valley floor soil (mine) with very poor
> mountain soils. 

OK.

> For antenna design it's the soil characteristics in the immediate vicinity
> of the antenna we need to know.  It's not very hard to make your own
> measurements and well worth the trouble.

Can you point me/us to an article on how to do this?

Ken W7EKB