ALE (Automatic Link Establishment)

Introduction to ALE (extracts from ARRL Web site) :

General : Automatic Link Establishment (ALE) was developed to automatically select a frequency that will support automatic linking between stations in a network or point-to-point communication.without operator assistance.
In high-frequency (HF) radio, ALE makes possible for a station to make contact, or initiate a circuit, between itself and another specified radio station, without human intervention and usually under processor control.

Allowed functions : ALE techniques include automatic signaling, selective calling, and automatic handshaking. Other automatic techniques that are related to ALE are automatic channel scanning, link quality analysis (LQA), polling, sounding, message store-and-forward, address protection, exchange of orderwire commands and messages.

- Standard mode
Description (standard) :
Baud rate : 125 bauds
Speed : about 76 wpm
Modulation : FSK 8 tones (3 bits)
Reception mode : only one side (USB or LSB), USB is recommended
Character set : ASCII characters
Shape of pulse : rectangular
Space between tones : 250 Hz,
Bandwidth : 2000 Hz,
Demodulation : non-coherent,
Synchronization : automatic using the signal
Coding : Golay and average on 3 frames (with a 2/3 voting logic)
Interleaving : yes (within a block of 48 bits)
Drift tolerance : 10 à 20 Hz/mn according to signal-to-noise ratio,
Pmean/Ppeak : 1
Lowest S/N : -4 dB

Note : pieces of information about this mode can be found on the FS-1045A specification ("Telecommunications: HF radio Automatic Link Establishment")

Before each frame, it is transmitted 12 symbols, alternately on the lowest frequency and then on the highest frequency, so for a duration of about 0.1 second (12/125 s). This is aimed to permit the symbol synchronization just before the frame reception. This does not exist within the FS-1045A specification:

More on ALE FAE ARQ CLICK HERE

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