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HF communications standards, created by the US Govern-ment, NATO, and other organizations, greatly influence the design of HF equipment and systems. These standards apply to equipment specifications, waveform design, communication protocols, and computer control. They serve to:

Ensure interoperability among systems used by different organizations.

Reduce ambiguous descriptions of equipment and systems by providing a common language in equipment specifications and in defining the operating environment.

Allow more accurate comparison between different equip-ment by defining test conditions.

A summary of some of the most important HF radio communi-cation
standards are:

Federal Standard 1045A, HF Radio Automatic Link Establishment. Specifies automated radio features, including frequency scanning, selective calling, ALE, LQA, and sounding, which ensure interoperability of radio systems.

Federal Standard 1052, HF Radio Modems. Defines design objectives for data modems and performance requirements for a data link protocol compatible with the ALE standards estab-lished by FED-STD 1045A.

MIL-STD-188-100 Notice 1, Common Long Haul and Tactical Communications System Technical Standards. Specifies requirements for interconnecting long-haul and tactical systems for voice and data service.

MIL-STD-188-110A, Interoperability and Performance Standards for Data Modems. Establishes requirements and design objectives that ensure specified levels of performance of voice-frequency data modems used in communications systems.

MIL-STD-188-141A, Interoperability and Performance Standards for Medium- and High-Frequency Radio Equipment. Establishes requirements and design objectives that ensure interoperability and specified levels of perfor-mance for HF radio equipment. Includes details about imple-menting
ALE systems, waveforms, signal structures, protocols, and LQA.

NATO STANAG 4285, Characteristics of 1200/2400/3600 bps Single-Tone Modulators/Demodulators for HF Radio Links. Defines the parameters that ensure interoperability between single-tone modems designed for communicating via HF radio links at bit rates of 1200, 2400, or 3600 bps.

NATO STANAG 4529, Modification of NATO STANAG 4285 to deliver data and voice in 1240 Hz bandwidth.