47 CFR § 73.510
Antenna systems
February 16, 2021
(a) All noncommercial educational stations operating with more than 10 watts transmitter output power shall be subject to the provisions of §73.316 concerning antenna systems contained in subpart B of this part.
(b) Directional antenna. No application for a construction permit of a new station, or change in channel, or change in an existing facility on the same channel will be accepted for filing if a directional antenna with a maximum-to-minimum ratio of more than 15 dB is proposed.
[42 FR 36829, July 18, 1977]