The ACARS system sends and receives communications through which channel?

The ACARS (Aircraft Communications Addressing and Reporting System) primarily utilizes VHF radio channels for its communications. In particular, it is commonly associated with VHF 1 and VHF 2. These VHF channels are well-suited for ACARS because they provide reliable line-of-sight communication capabilities that enable data transmissions and message receptions between aircraft and ground stations.

While HF (High Frequency) radio is used for long-range communications, it is not typically employed for ACARS due to its various limitations and the advantageous characteristics of VHF channels in aviation environments. HF radio can be subject to atmospheric conditions, leading to variable quality and availability, which does not align with the need for reliable and timely data exchange required by ACARS.

Therefore, the correct perception is that ACARS communicates over VHF channels, specifically using VHF 1 or VHF 2, rather than VHF 3 or HF radio.