[IRCA] Max. Groundwave Propagation Distance?

[JKi5384486@xxxxxxx]

Jeff,
That's a tough one to summarize quickly.  Yes on of the factors is  
frequency, the lower on the dial the better
but more importantly the conductivity of the soil.
The FCC years ago published a conductivity map for the US which you  can 
download on their website.
It ranges for .5 to 30 over land.  Long Island and around Atlanta have  some 
of the worst conductivity.  Parts of the midwest and Texas are at or  near 30.
As a rule of thumb you occasionally find an area that matches the map but  
for the most part signal strength measurements  show the conductivity is a  lot 
less.  Most of Dallas for example is in a 30 but in reality is about a  four 
to a seven.
The real champ is the ocean rated at 5000.  A good example, Radio  Vision 
Christiana  in the Turks and Caicos on 530 can be heard along  Florida's east 
coast during the day as far north as St. Augustine, well over 700  miles thanks 
to the great conductivity.  I have personally listened during  midday to 
WMEN/640 from Royal Palm Beach, Fla in the Dominican Republic several  times which 
is pushing 800 miles.  About the best you'll find in the US is  a low frequency 
station getting 300 miles ground wave.
The more hills in the terrain the worst the conductivity, flat pasture land  
with fertile soil is the best, an exception being the Florida Everglades, 
rated  at an eight but more like a 15 due to the swampy soil.
Sand makes a lousy conductor as illustrated by the coastal area from New  
York to Florida.
Where I live we are in a 15 but a few miles north it's an eight and a few  
miles west it goes down to a          four as you head towards the mountains.  
The changes come gradually from  one conductivity to another.
Jerry Kiefer
Roswell, NM



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