[600MRG] FCC maps

[Marshall Cross]

Hi Rudy, I was about to send out an email saying what you said but better than I ever could. 73, Marshall W1HK, #41

Sent from my iPhone

> On Feb 5, 2016, at 12:36 PM, Rudy Severns <n6lf at epud.net> wrote:
> 
> 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
> 
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