WASHINGTON (AP) _ Radio Marti, the Reagan administration's bid to broadcast the ''truth'' to the Cuban people, is still silent 14 months after being authorized, causing widespread uneasiness among its supporters.

Officials at the station have decided not to go on the air until it is ready to fulfill its target of 141/2 broadcast hours daily. Some have urged that the station begin operations immediately with a less ambitious schedule.

''We are ready to go on the air 6 to 7 hours a day,'' said one disgruntled official at Voice of America, the agency responsible for station.

The official purpose of Radio Marti is to give the people of Cuba an alternate source of information. Since the revolution, all media in Cuba have been under strict government control, and the editorial line is decidedly anti-American.

Last Nov. 28, President Reagan told Sen. Paula Hawkins, R-Fla., that he knew of no reason why the station could not go on the air on Jan. 28, the anniversary of Marti's birth, according to an aide to the senator. But officials at the station said no target date has been set.

In a statement Thursday, Mrs. Hawkins said, ''Radio Marti could broadcast several hours of material a day starting Jan. 28. This would be an effective way to celebrate the birth of Cuba's greatest freedom fighter.

''Quality broadcast material is on the shelf; the Cuban people are ready, and I feel Radio Marti is also.''

Marti was a 19th Century Cuban patriot who fought Spanish rule.

Also expressing concern to Reagan over the delay have been Rep. Dante Fascell, D-Fla., Sen. Lawton Chiles, D-Fla., Sen. Steve Symms, R-Idaho, and Rep. Jack Kemp, R-N.Y.

Six weeks ago, Fascell, a Miami Democrat who is chairman of the House Foreign Affairs Committee, wrote a letter to Reagan expressing ''deep disappointment'' over the delay. Charles Z. Wick, director of the U.S. Information Agency, which oversees VOA, sent a letter to Fascell on Thursday promising him all is being done to get the station on the air ''as quickly as possible,'' Fascell's office said Friday.

''The time frame at the Radio Marti Program compares favorably with the time required to start a new language service at the VOA, the BBC and Radio Free Europe-Radio Liberty,'' Wick wrote.

''It is one thing to have the right kind of substantive programming capability, which indeed we have assembled. It is another thing to have it broadcast professionally.''

Rogene Waite, a VOA spokeswoman, said another problem involves getting security clearances for scores of prospective employees, many of whom were born in Cuba. Ensuring that those hired will be trustworthy is a ''horrendous'' task, she said, adding, ''The hiring process takes time.''

Of the 188 employees authorized by Congress, the station has hired about 100, Ms. Waite said. The candidates for the remaining positions, she added, are undergoing security checks or are ''under evaluation.''

In his letter to Fascell, Wick also acknowledged he has had difficulty finding a director for Radio Marti.

One prospective director was dropped last year after failing to reach an agreement with VOA over moving his family to Washington. In December, veteran broadcaster Paul Drew was named director but left the post for unexplained reasons after just a month on the job. A replacement has not yet been named.

The station plans to offer a mixture of music, news and commentary, with emphasis on issues normally not discussed in the Cuban media. One such issue is the situation in Angola, rarely mentioned in the Cuban media even though Cuba has more than 20,000 troops stationed there. Also planned are in-depth reports on other troubled Soviet bloc countries, including Ethiopia and Poland.

A VOA official, who spoke only on condition of not being identified, said Cuba has been upgrading its entertainment fare at movie theaters and on television recently, apparently concerned that many Cubans may tune in Radio Marti once its programming begins. The official said more first-run American movies are being shown in Cuban theaters than before.

The official said there has been surprisingly little disagreement over the content of Radio Marti programming. The most contentious debate focussed on whether President Fidel Castro should be referred to as ''President Castro'' or just ''Castro.'' The latter option was chosen, he said.

One administration concern is just what Castro will do once the station finally becomes operational. Some VOA officials predict a ''radio war,'' with Cuba using its powerful transmitters to jam U.S. commercial stations.

When Radio Marti was under debate in Congress two years ago, Cuba, in what was viewed as a warning, beamed music and propaganda that were heard on American stations ranging from south Florida to Salt Lake City.