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.