Links for HF ALE
About ALE - Quoted from wikipedia.org - Automatic Link Establishment
Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system, that enables the radio station to make contact, or initiate a circuit, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels.
How ALE Works
A standalone ALE radio combines an HF SSB radio transceiver with an internal microprocessor and MFSK modem. It is programmed with a unique ALE Address, similar to a phone number (or on newer generations, a username). When not actively in contact with another station, the HF SSB transceiver constantly scans through a list of HF frequencies called channels, listening for any ALE signals transmitted by other radio stations. It decodes calls and soundings sent by other stations and uses the Bit error rate to store a quality score for that frequency and sender-address.
To reach a specific station, the caller enters the ALE Address. On many ALE radios this is similar to dialing a phone number. The ALE controller selects the best available idle channel for that destination address. After confirming the channel is indeed idle, it then sends a brief selective calling signal identifying the intended recipient. When the distant scanning station detects ALE activity, it stops scanning and stays on that channel until it can confirm whether or not the call it for it. The two stations' ALE controllers automatically handshake to confirm that a link of sufficient quality has been established, then notify the operators that the link is up. If the callee fails to respond or the handshaking fails, the originating ALE node usually selects another frequency either at random or by making a guess of varying sophistication.
Upon successful linking, the receiving station generally emits an audible alarm and shows a visual alert to the operator, thus indicating the incoming call. It also indicates the callsign or other identifying information of the linked station, similar to Caller ID. The operator then un-mutes the radio and answers the call then can talk in a regular conversation or negotiates a data link using voice or the ALE built-in short text message format. Alternatively, digital data can be exchanged via a built-in or external modem (such as a STANAG 5066 or MIL-STD-188-110B serial tone modem)depending on needs and availability. The ALE built-in text messaging facility can be used to transfer short text messages as an "orderwire" to allow operators to coordinate external equipment such as phone patches or non-embedded digital links, or for short tactical messages.
To top of this page
ALE use in international amateur radio
Amateur Radio operators began sporadic ALE operation on a limited basis in the early to mid 1990s, with commercial ALE radios and ALE controllers. In 2000, the first widely available software ALE controller for the Personal Computer, PCALE, became available, and hams started to set up stations based on it. In 2001, the first organized and coordinated global ALE nets for International Amateur Radio began. In August 2005, ham radio operators supporting communications for emergency Red Cross shelters used ALE for Disaster Relief operations during the Hurricane Katrina disaster. After the event, hams developed more permanent ALE emergency/disaster relief networks, including internet connectivity, with a focus on interoperation between organizations. The amateur radio 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 interoperably. Amateur radio operators may use it to call each other for voice or data communications.
ALE adaptations to amateur radio for interoperability
Amateur radio operators commonly provide local, regional, national, and international emergency / disaster relief communications. The need for interoperability on HF led to adaption of Automatic Link Establishment ALE open networks by hams. Amateur radio adapted 2G ALE techniques, by utilizing a common denominator the 2G ALE protocol, with a limited subset of features found in the majority of all ALE radios and controllers. Each amateur radio ALE station uses the operator's callsign as the address, also known as the ALE Address, in the ALE radio controller. The lowest common denominator technique enables any manufacturer's radios or software to be utilized for interoperative communication and networking. Known as Ham-Friendly ALE, the amateur radio ALE standard is used to establish radio-communications, through a combination of active ALE on internationally recognized automatic data frequencies, and passive ALE scanning on voice channels and all other channels. In this technique, active ALE frequencies include pseudo-random periodic polite station identification, while passive ALE frequencies are silently scanned for selective calling. Ham-Friendly ALE technique is also known as 2.5G ALE, because it maintains 2G ALE compatibility while employing some of the adaptive channel management features of 3G ALE, but without the accurate GPS time synchronization of 3G ALE.
End of quote from wikipedia.org
To top of this page
ALE Links
HFLink - International resource for ALE Automatic Link Establishment High Frequency Communications
Homepage for Amateur Radio ALE Comms
Wikipedia - ALE background and information
ARRL Technical Information Service Page on ALE
High-frequency Radio Automatic Link Establishment (ALE) Application Handbook, September 1998
HFLink - Ham Radio ALE High Frequency Network
HFLink - ALE Channel List - Ham Radio
HFLink - Hardware Recommended for Use With PCALE
HFLink - ALE Software