Howard Walker, an electronics buff, says he saw it as a challenge: Could he build a homemade decoder that would unscramble Super TV's signal?

"Why does a person climb a mountain? Because it's there," says Walker, 31, a communications satellite company technician whose small Manassas Park home is packed with radio, television and computer gadgetry. "I did it just for the hell of it."

The McLean-based pay-television company that broadcasts Super TV viewed it differently. The year-old firm, which claims nearly 70,000 subscribers in the Washington and Baltimore areas, sued Walker for $1.25 million, accusing him of engaging in criminal piracy by assembling and selling decoders to homeowners who wanted to watch Super TV without paying its $24.90-a-month fees.

The pay-TV industry contends it is plagued by illegal pirating. "What we're trying to do at this point is get a handle on it very early," said Ric Clay, Super TV's operations director. He promised aggressive legal actions against any "black market" dealer uncovered by his company.

The federal court contest--one of a growing number of lawsuits and criminal prosecutions here and across the nation--provides a tale of human ingenuity and corporate detective work in the booming, rapidly changing telecommunications arena. Super TV broadcasts movies, sports events, adult movies, and other special programs over Channel 50 to Washington-area subscribers, chiefly during evening hours.

"They're using an elephant gun on a gnat. I'm not a threat to them," complained Walker during an interview at his suburban home, which is overshadowed by radio and television towers. "I didn't think I was doing anything wrong. I guess I'm a babe in the woods or very naive."

Walker, a college dropout who earns about $28,000 a year working for TeleSystems Inc., a Comsat subsidiary, was lured into electronics by radio-repair training he received in the Air Force in the mid-1970s. Since then, he said, he has also worked for six other Washington-area firms and briefly free-lanced as a communications contractor.

In his spare hours, he installed a homemade computer beside his front door and used it to help his older son with schoolwork. He is a ham radio operator. In a tiny workroom jammed with circuit boards, tuners and other devices, Walker is currently trying to rebuild a 1951 circular-tubed Capehart-Farnsworth Corp. television set--a collector's item, he said.

Walker started trying to break Super TV's code, he said, about the time the pay-TV company began broadcasting in November 1981. The project was to occupy his evenings for months. He hooked up a tuner and an oscilloscope to study the scrambled signal, watching the play of green lights on a picture tube. His system, he said, was to "hunt and peck."

A breakthrough occurred, he said, when he accidently spotted a single television line--one of 262 on a TV screen--that carried clues to unlocking the code. This line, he said, "gives it away." Then he began putting together his decoder, a small rectangular box filled with circuits. By early summer, he had succeeded.

"The first thing I remember seeing was Beatles singer Paul McCartney's face. I said: 'God, it works.' It's great," Walker recalled. "I was overwhelmed. After all this time, I finally did it."

Walker invited friends to see his little contraption. Soon, he said, he got telephone calls from acquaintances and others who had heard about his decoder. They had been turned down by Super TV, he said, because they lived too far away from the station's transmitter in Northwest Washington for adequate reception. He suggested installing bigger antennas and amplifiers and eventually, he said, he built decoders for some of them.

Walker sold the decoders to about 12 to 15 homeowners in Fauquier and Loudoun counties, he said, for $350 to $375 each--about what the equipment cost him. He contended that all the decoders went to homeowners previously rebuffed by Super TV--a statement that operations chief Clay later challenged. One Fauquier resident, who asked not to be identified, said in an interview that Walker sold her a decoder only after she was twice rejected by Super TV.

According to affidavits filed with the lawsuit in U.S. District Court in Alexandria, the company learned about Walker's decoder through an anonymous tip from a Citizens Band radio buff, who claimed 10 to 15 pirate decoders were being sold weekly. Walker denies that.

In November, according to the affidavits, a Super TV employe, posing as a customer and accompanied by a plain clothes Manassas Park policeman, bought a decoder from Walker for $375. Subscription Television of Greater Washington, the firm that broadcasts Super TV, went to court and was granted a temporary restraining order. The Dec. 22 order, issued by Judge Richard L. Williams, bars Walker from further decoder operations.

One affidavit quoted Walker as telling the Super TV employe posing as a customer: "I got 10 coming up tomorrow--got to get ready for the Christmas rush." In an interview Walker described the remark as a joke.

"There is a booming business in this country with pirates," contended William Wewer, Super TV's lawyer and general counsel for the Subscription Television Association, a national industry group. Wewer cited lawsuits by pay-TV broadcasters in New York, Detroit, Los Angeles and Phoenix and said there may already be as many as 500,000 or more illegal decoders in use.

Although the suit against Walker was the first filed by the McLean firm for alleged piracy, several similar court actions have been brought by Washington-area pay TV firms.

Marquee Television Network, a Rockville pay-TV firm, won more than $100,000 in damages last June in a federal court suit against a District of Columbia company engaged in sales of rooftop antennas that intercepted its signals. An Arlington woman pleaded guilty in November to charges of illegally tapping into the Arlington TeleCommunications Corp. (ARTEC) cable TV system.

Walker does not regard himself as a pirate. "I've done this as a hobby," he said. "I don't have anything to hide. I don't have a large installation going. To tell you the truth, I'm scared to death."

The $1.25 million lawsuit has stunned him. "It's a bad dream," Walker said. "It's more than I'll ever make in my life."