Transmit range

I know it is the most asked question "How far can I transmit?" This formula is for seagoing craft so it applies to circle, flat with no obstructions, terrain etc.

Range in miles = 1.6 times the square root of your antenna height above surface. Example- an antenna 100 feet above the surface would have a range of 16 miles. This is for HF radio and does not allow for "skip" or other reflection of signal.

If the antenna of the receiver were 100 feet up, you would have a range of about 30 miles. The receiver antenna would have a line of sight on the transmitted signal. "A transmitted signal has a slight bend over the horizon"

Line of sight over water is 1.4 times the square root of height above water. A six foot tall man standing on the surface would have a horizon of about 3.4 miles. A hand held transmitter would have a range of about 3.9 miles when held at eye level.