Before revision: In the United States, Part 15 of the U.S. Federal Communications Commission rules specifies that no license is needed if range of the transmitter does not exceed , although the Part 15 rules specify that the field strength should not exceed 250 µV/m (48db) at 3 meters, which is less than the service contour for commercial stations (60db), necessary for the satisfactory reception of FM stereo .
After revision: In the United States, Part 15 of the U.S. Federal Communications Commission rules specifies that no license is needed if range of the transmitter does not exceed , although the Part 15 rules specify that the field strength should not exceed 250 µV/m (48db) at 3 meters, equivalent to 0.01 microwatts ERP (actual power varies depending on the antenna length) .