Radiation Systems Inc. of Sterling was awarded a $34.4 million contract from Unisys Corp. for the manufacture and testing of 37 radar array antenna transmitters for the U.S. Air Force's North Warning System, for which Unisys was awarded the production contract.

The system's 37 unmanned antennas in the Arctic will be used to detect low-flying cruise missiles in the Northern Hemisphere, specifically coming from the Soviet Union, according to Radiation Systems President Richard Thomas.

Radiation Systems, which had revenue last year of $85.2 million, has been expecting this contract for almost two years. From 1986 to 1988 the firm manufactured and tested three engineering development models for Unisys as part of the initial operation phases leading to the award of the production contract.

Maryland Environmental Systems Inc. of Columbia, Md., a commercial and residential heating, ventilating and air conditioning contractor, acquired Baltimore-based Mechanical Services Inc., which provides commercial plumbing services in addition to heating and air conditioning. Terms were not disclosed.

Before the acquisition, Mechanical Services had about 25 employees. According to a company spokesman, Maryland Environmental, which now has 150 employees, acquired the firm because of its plumbing capabilities and its variety of commercial contracts.

Creative Communications Inc. of East Providence, R.I., an international corporate communications firm, acquired International Communications Group Ltd. of Falls Church for an undisclosed amount. International Communications Group is a media consulting firm with about five employees.

Creative Communications produces the nationally syndicated program "Crime Stoppers 800"and has offices in Detroit and London.

InterCon Systems Corp. of Herndon and Performance Systems International of Reston entered a joint-development agreement aimed at improving a system they created that allows users on Apple's Macintosh computers to access the Internet network with full TCP/IP and OSI capabilities.

Performance Systems International provides the dial-up service for local Macintosh users to access Internet, and InterCon provides the applicable based software. A spokesman for Performance Systems said the new agreement, which also includes a provision for the companies to market each other's products, is aimed at improving the overall quality of the system.

Hughes Network Systems Inc. of Germantown was awarded a contract by Datacom Technologies Ltd. of Wellington, New Zealand, to supply advanced packet switching equipment for Datanet, a packet-switching network used by the New Zealand government and private customers. The contract is initially valued at $400,000.

Ogden/ERC Government Systems of Fairfax, a subsidiary of New York-based Ogden Corp., was awarded a subcontract by KPMG Peat Marwick to support the acquisition and implementation of a new integrated financial management information system for the Department of Agriculture's Food and Nutrition Service. The contract is worth up to $1.2 million over four years, with options for additional years of services.

Caterair International Corp. of Washington was awarded a contract by Canadian Airlines to provide meals to the company's aircraft in Vancouver, Calgary, Toronto and Montreal. As part of the agreement, Caterair will build a flight kitchen in Vancouver, which will include a section to prepare Japanese food. Terms of the contract were not disclosed.

Announcements of news and developments affecting Washington area companies should be sent to Regional Report, Business News Department, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.