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Saturday, December 31, 2011

Automatic Link Establishment

Each radio ALE station uses a callsign or address in the ALE controller.When not actively in communication with another station, each HF SSB transceiver constantly scans through a list of frequencies, listening for its callsign. To reach a specific station, the caller simply enters the callsign just like dialing a phone number. The ALE controller selects the best available frequency and sends out brief digital selective calling signals containing the callsigns. When the distant scanning station detects the first few characters of its callsign, it stops scanning and stays on that frequency. The two stations’ ALE controllers automatically handshake to confirm that a link is established and they are ready to communicate. The receiving station, which was muted up until now, will typically emit an audible alarm and visual alert for the receiving operator of the incoming call. It also indicates the callsign of the linked station. The operators then can talk in a regular conversation. At the conclusion of the QSO, one of the stations sends a disconnect signal to the other station, and they each return their ALE stations to the scanning mode. Some military / commercial HF transceivers are available with ALE options. Amateur radio operators commonly use the PCALE soundcard software ALE controller, interfaced to a ham transceiver via RS-232 CAT port, multi-frequency antenna. Automatic Link Establishment is a great tool for the purpose of communicating between stations in real-time, while avoiding guesswork, beacon listening, and complicated HF prediction charts altogether. ALE is most commonly used for hooking up operators for voice communications on SSB and for internet messaging, but there are many other useful features.

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