FM broadcasting
VHF Radio waves do not travel far beyond the visual horizon, so reception distances for FM stations are usually limited to 30–40 miles (50–65 km) They can also be blocked by hills or buildings.
Title 47 CFR Part 15
Unlicensed broadcasts on the FM broadcast band (88 to 108 MHz) are limited to a field strength of 250 µV/m at a distance of 3 meters from the antenna. This is roughly equivalent to 0.01 microwatts. Emissions must be kept within the 88.0 to 108.0 MHz band under Part 15 rules.