[600MRG] FCC maps

[Rudy Severns]

Thanks very much Steve for the link.  

 

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!

 

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. 

 

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.

 

73, Rudy N6LF