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Old 01-14-2010, 1:58 PM
SkipSanders SkipSanders is offline
Silent Key
Join Date: Dec 2002
Posts: 1,125

Once you have 1-2 watts of power at VHF, and especially at UHF (Like the FRS radios mentioned), power is almost meaningless.

Line of Sight is everything.

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.

Meanwhile, I had no trouble talking to a station 150 miles away, with 2 watts... oh, it happened that the other station was on the Space Shuttle, though...

I had no trouble talking to/through a ham VHF repeater 16 miles away, with 100 milliwatts... because it was at a good high mountain, and I'm at a 250 foot level, with no obstructions between.

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.

A pair of handie talkies: Antenna height, 5 feet. Range, 2.24 miles (each), for (call it) 4.5 miles expected reliable range. This is only over flat, unobstructed ground, though. Buildings and hills obstruct. At UHF, trees aren't helpful, either.

Now have one end stand on a 200 foot hill. Combining the two again, 16.5 miles.

Now, in reality, you may see as much as double this range, in perfect conditions. In not so perfect conditions, you may see half... or less.

Typical urban setting range between handie talkies is 1/2 to 1 mile, maybe 2 miles if you're lucky.
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