The Senate on Thursday added $2.5 million to a defense spending bill to evaluate a low-profile tactical radio antenna design developed by the Eyring Research Co., of Provo. The money, inserted in the bill at the request of Sen. Jake Garn, R-Utah, would be split between the Army and the Air Force, Garn said, to pay for competitively bid contracts for production of test quantities of such antennas. The winning bidder would be required to match the federal funds.

Eyring Research is likely to get both awards, as the company has developed the UHF/VHF design, an aide to Garn said. The coil-shaped antennas are said to be less visible in forward combat areas than conventional antennas.Eyring Research, bought recently by John Harmer, has been working on the design for four years. A Garn aide said the antenna has been successfully tested but that Pentagon procurement agents have given spending priority to service-developed projects. Congress added $17.5 million to the defense bill this week to test similar small-company military equipment that has been refused by the Defense Department.