WASHINGTON (AP) _ Plough Broadcasting Co., Inc. is eligible for the first federal reimbursement of the cost of offsetting the effects of Cuban radio jamming, the Federal Communications Commission ruled Tuesday.

The $12,265 claim was for money Plough spent to modify its transmitting facilities to offset the effects of interference on its St. Petersburg, Fla., radio station WSUN, an AM station that Plough has since sold.

The fund to pay such claims was set up in the Radio Broadcasting to Cuba Act of 1983, which also created Radio Marti to broadcast news directly to Cuba from transmitters at Marathon, Fla.

Radio Marti is not yet on the air, although its Senate sponsor, Paula Hawkins R-Fla., had predicted it would start service by Christmas 1983.

The official purpose of Radio Marti is to give the people of Cuba an alternative source of information. Its inauguration has been delayed by difficulty in getting security clearances for enough employees to keep the station on the air for 141/2 hours a day, according to the Voice of America, which is responsible for running the station.

Since the revolution, all media in Cuba has been under strict government control.

WSUN was allowed to increase its power to combat interference from Cuban transmitters on June 3, 1983.

Cuba has threatened to use powerful transmitters to jam the broadcasts of U.S. commercial stations as retaliation for Radio Marti. The Castro government did just that one night during congressional debate on establishing Radio Marti, beaming music and propaganda that were heard on American stations from south Florida to Salt Lake City.

Money to pay the compensation comes from VOA, which must approve the claim and find the money to pay it.