Section 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 points1
(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.
48 FR 50333, Nov. 1, 1983, as amended at 49 FR 7130, Feb. 27, 1984; 50 FR 48599, Nov. 26, 1985; 51 FR 19840, June 3, 1986; 62 FR 4922, Feb. 3, 1997; 68 FR 12767 , Mar. 17, 2003