Section 73.510 - Antenna systems(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