Broadcast
A broadcast is a transmission of information not directed to a specific station or requiring a response. In aviation, pilots make position broadcasts on ATF and MF frequencies to advise other traffic of their position and intentions. ATC makes general broadcasts (e.g., weather alerts, PIREP dissemination) on guard (121.5 MHz) or other designated frequencies.
Types of Aviation Broadcasts
- ATF/MF self-announcement: Pilot broadcasts position, altitude, and intentions to other traffic in the circuit area
- UNICOM advisory: Ground station broadcasts runway and weather information
- ATIS broadcast: Automated continuous recording of airport weather, active runway, and NOTAMs
- Guard frequency broadcast: Urgency or distress traffic; also used for position broadcasts when no other frequency is available
Blind Transmission
A blind transmission is a broadcast made when two-way communication cannot be established, in the hope that the other station can receive even if it cannot transmit. ATC may issue a blind transmission to an aircraft that has lost its transmitter but may still be able to receive.