47 CFR 74.536: Directional antenna required.

(a) Aural broadcast STL and ICR stations are required to use a directional antenna with the minimum beamwidth necessary, consistent with good engineering practice, to establish the link.

(b) An aural broadcast STL or intercity relay station operating in the 17.7-19.7 GHz band shall employ an antenna that meets the performance standards for Category A, except that in areas not subject to frequency congestion, antennas meeting standards for Category B may be employed. However, the Commission may require the replacement, at the licensee's expense, of any antenna or periscope antenna system of a permanent fixed station that does not meet performance Standard A, which is specified in the table in paragraph (c) of this section, upon a showing that said antenna causes or is likely to cause interference to (or receive interference from) any other authorized or proposed station; provided that an antenna meeting performance Standard A is unlikely to involve such interference.

(c) Licensees shall comply with the antenna standards table shown in this paragraph in the following manner:

(1) With either the maximum beamwidth to 3 dB points requirement or with the minimum antenna gain requirement; and

(2) With the minimum radiation suppression to angle requirement.

Antenna Standards

Frequency (GHz) Category Maximum beamwidth to 3 dB points 1 (included angle in degrees) Minimum antenna gain (dbi) Minimum radiation suppression to angle in degrees from centerline of main beam in decibels

5° to 10° 10° to 15° 15° to 20° 20° to 30° 30° to 100° 100° to 140° 140° to 180°

17.7 to 19.7 A B 2.2 2.2 38 38 25 20 29 24 33 28 36 32 42 35 55 36 55 36

1 If a licensee chooses to show compliance using maximum beamwidth to 3 dB points, the beamwidth limit shall apply in both the azimuth and the elevation planes.