> >> As a quick and dirty method, the radio horizon (RH) is: > >> > >> Distance (in miles) = Square Root of (2 * height in feet).
> This equation is ok, but for a perfect spheer. Is a good place to >start. Here in FL where max altitude is about 330 ft ASL it works >pretty well although the lower the antenna the worse the actual >coverage results. We have plenty of repeaters at 200 ft that have >noticably better coverage than 20 miles with a mobile. I agree that it's not the perfect formula, but if someone is asking the question of how much power do I need, then they need to look at the height formula first to get them in the ball park. When it comes to range, nothing matters more than height. Doubling the height increases the range by about 50%. With power, you have to 10 times the effective power to double the range (until the RH limit). Since the original question was for flat terrain, the RH will be real close. HAAT = AGL. Dwayne Kincaid WD8OYG
