Section 87.349 - Frequencies(a) The frequency assigned to an aeronautical utility station at an airport served by a control tower, RCO or FAA flight service station is the frequency used by the control tower for ground traffic control or by the flight service station for communications with vehicles. In addition to the ground control frequency, an aeronautical utility station at an airport served by a control tower or RCO may be assigned the tower or RCO frequency if the assignment is specifically approved by the FAA as provided for in § 87.347(c) . The frequencies assigned are normally from the band 121.600-121.925 MHz.(b) The frequency assigned to the unicom is available to aeronautical utility stations on a noninterference basis at airports which have a part-time control tower, part-time RCO or part-time FAA flight service station and a unicom.(c) At airports which have a unicom but no control tower, RCO or FAA flight service station, the frequency assigned to the unicom is available to aeronautical utility stations on a noninterference basis. The frequencies available for assignment to unicoms are described in subpart G of this part.(d) At airports which have no control tower, RCO, flight service station or unicom, the frequency 122.900 MHz is available for assignment to aeronautical utility stations.(e) The frequency 978.0 MHz is authorized for Universal Access Transceiver data transmission.(f) The Commission will assign frequency 1090 MHz for use by aeronautical utility mobile stations for ground vehicle identification and collision avoidance after coordination with the FAA, subject to the following conditions:(1) The applicant must notify the appropriate Regional Office of the FAA prior to submission to the Commission of an application for a new station or for modification of an existing station. Each application must include the FAA Regional Office notified and date of notification.(2) Eligibility is restricted to airport operators holding an FAA Airport Operating Certificate, and other entities approved by the FAA on a case-by-case basis to use frequency 1090 MHz for use by aeronautical utility mobile stations for ground vehicle identification and collision avoidance;(3) No more than two hundred 1090 MHz aeronautical utility mobile stations will be authorized at one airport;(4) Licenses are limited to only those locations that are within the vicinity of an FAA ASDE-X multilateration system or ADS-B equipment, and/or where the primary purpose for seeking transmit authorization is to provide surface data to aircraft and air traffic control authorities.(5) Message transmission rates are limited as indicated in the table below: | ADS-B Message | Rate when moving | Rate when stationary |
| Surface Position Message (Types 5, 6, 7, 8) | Every 0.4 to 0.6 seconds | Every 4.8 to 5.2 seconds. |
| Aircraft Operational Status (Type 31) | Every 4.8 to 5.2 seconds | Every 4.8 to 5.2 seconds. |
| Aircraft Identification and Type (Type 2) | Every 4.8 to 5.2 seconds | Every 9.8 to 10.2 seconds. |
55 FR 30464, July 26, 1990, as amended at 55 FR 30908, July 30, 1990; 71 FR 70680 , Dec. 6, 2006; 78 FR 61207 , Oct. 3, 2013