|RTTY & Facsimile Equipment|
ACARS (Aircraft Communications Addressing and Reporting System) is a radioteletype mode developed in the early eighties as an addressable, digital data link for commercial and business aircraft. It was produced to reduce the flight crew's work-load by using modern computer technology to exchange many routine reports and messages. This improves the safety and efficiency of modern air travel.
ACARS uses the AM mode because the same airborne VHF radio is often also used for voice communications. Burst transmissions are used with a limit of 220 characters per message. Transmissions often last less than one second! Therefore when monitoring ACARS it is important to leave your receiver's squelch off. To monitor ACARS transmissions you will need a VHF scanner or receiver capable of tuning the VHF (AM) aircraft band 118 to 136 MHz and a decoder such as the ARD-2 to decode and display (or print) the text messages.
ACARS messages are very structured. Each position in the message has a specific function.