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Old 01-14-2010, 6:55 PM
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gmclam gmclam is offline
Join Date: Sep 2006
Location: Fair Oaks, CA
Posts: 5,314
Smile It's not the power, it's antenna height!

Originally Posted by kb2vxa View Post
Relaying this information from reliable engineering sources the rule of thumb is one mile per watt effective radiated power direct line of sight on VHF FM.
That seems unrealistic. Consider that NOAA transmitter not too far from here, high on a mountain top, with 100K of power, on 162.400 or 162.550 MHz broadcasting on a 15khz wide channel. They don't go 100 miles, let alone 100,000.

Originally Posted by SkipSanders
Let's see, if it's 1 watt = 1 mile, my, that means that a nice FM broadcaster, with 5000 watts, can get 5000 miles... nope. 40 miles, maybe. Maybe 90, if they have a good high antenna site.
Another thing to consider is bandwidth. Commercial FM broadcasters are using 200khz wide channels, not 10,15,or 25khz wide.

Originally Posted by SkipSanders
The only rule of thumb I've seen from Motorola was one using antenna height, not power.

Take the height of your antenna in feet. Find the square root. That's your expected reliable range in miles. Do the same for the antenna on the other end, add the two results.
I totally agree.
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