[BC] Signal Strength Question

[Tom Spencer]

I've been working with the folks who are programming one of the two AM 
stations on Key West - the one on 1500; 250 watts DA-1, a figure-8 
pattern along the length of the island, TX at the isthmus.  The other 
station is on 1600, ND, with 500 watts, and from the pattern, most of 
that 500 watts is being received by the fishies... (and yes, 1500 is 
using SPL :-P )

For an FM, depending on exactly where, once you're clear of the mainland 
6 kW at 100 meters should cover it all quite well; if you're trying for 
ALL of the keys, say from Marathon trying to hit Key West, then yeah, 
you'd need a bit more altitude and/or power...

A C3 would get just over 50 miles to the 100 microvolt (40 dBu) curve - 
and since that's over the ocean, it doesn't get much flatter, so the 
range predictor programs should be pretty close.  That puts the western 
beaches of Key West right at the 40 dBu curve, BTW.  A half-power C2 
would give a bit more range (25 kW @ 150 m); about 5 or 6 miles; a full 
- power C2 should make it over 60 miles - but MOST of that is the 
fishies... or the fishing boats.

Now, if you want to reach the Dry Tortugas from Marathon (120 miles)... 
you'd need to move the TX to Key West. <grin>.  A full powered C is just 
over 70 miles to the 40 dBu curve.  And would you want a 300 meter / 
1000 ft tower in the heart of hurricane country?  on an island?  I'm not 
sure even a B-K tower could handle the winds at that altitude; although 
there probably are some towers that tall near Miami or Tampa...

--
Tom S