In high-frequency (HF) radio automatic link establishment, the wildcard character "?"

Usually associated with Automatic Link Establishment and HF radio data communications.

Automatic link establishment (ALE) has enabled continuous amateur radio networks to operate on the high frequency bands with global coverage.

ALE (Automatic Link Establishment)

Automatic soundings are primarily intended to increase the efficiency of the automatic link establishment (ALE) function, thereby increasing system throughput.

ALE (Automatic link establishment) is a protocol developed by the USA military and used mainly as an automatic signalling system between radios.

The need for interoperability on HF led to adaption of Automatic Link Establishment ALE open networks by hams.

Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications.

High Frequency Single sideband / Automatic link establishment (HF SSB/ALE)

See HFLINK for more information about Amateur Radio ALE Automatic Link Establishment.

The HF modem technologies include PACTOR, Winmor, and Automatic Link Establishment (ALE).

Data transmission may make use of encrypted RTTY, use Link-11 for radar tracking data, or use of Automatic link establishment modes to set up communication links automatically.

Note: In adaptive HF radio automatic link establishment, PBER is determined by the extent of error correction, such as by using the fraction of non-unanimous votes in the 2-of-3 majority decoder.

However, the development of Automatic Link Establishment technology based on MIL-STD-188-141 for automated connectivity and frequency selection, along with the high costs of satellite usage, have led to a renaissance in HF usage in government networks.

An amateur radio HFIP network called HFLINK uses Automatic Link Establishment for initiating data communications, with ARQ 8FSK frequency shift keying and PSK phase shift keying signals.

The amateur radio HFLink Automatic Link Establishment system uses an open net protocol to enable all amateur radio operators and amateur radio nets worldwide to participate in ALE and share the same ALE channels legally and interoperably.