"The Free Voice of Iran" came through loud and clear tonight, broadcasting a mixture of news, reviews and music not found on Iran's official Islamic radio station.

Beamed from outside the country -- probably Iraq, though some speculate it comes from a ship in the Persian Gulf -- the station carried a message from the "army for the liberation of Iran" which said the present Iranian government led by Ayatollah Ruhollah Khomeini, is "racist and fascist" and will be overthrown very soon.

"This is the time to take guns in your hands. This is the duty of all Iranians," continued the broadcast in a manner reminiscent of Western programs beamed to Eastern Europe in the 1950s that encouraged Hungarian freedom fighters to attack Soviet tanks in the vain hope that help from the West would soon be coming.

While the radio broadcasts, which are believed to have started earlier this month, are listened to here, there is little indication that the call to arms is being heeded, except, in the rebellious provinces of Kurdistan and Khuzestan which were fighting for greater autonomy long before the clandestine station went on the air.

This lack of support for rebellion does not mean complete and widespread favor for the authorities currently running Iran. Increasingly, discontent is heard in the streets and the bazaars as well as among middle- and upper class Iranians who miss the good life.

This discontent -- based mainly on sharply rising prices and the inability of the authorities to ease unemployment -- is not aimed at Khomeini, the country's religious and political leader who has attained the status here of a demigod, but at the people around him.

There appears to be little if any support for the return of the deposed shah, who was overthrown and forced into exile 15 months ago.

Nonetheless, the broadcasts reinforce the fears of many Iranians who support the present Islamic revolution that the United States is fueling insurgent activities in an effort to return the shah to the throne, the way it did in 1953 when a CIA-led coup overthrew Prime Minister Mohammed Mossadegh and restored the shah to power.

This fear, in the eyes of most analyst here, is real and pervasive.

"Everybody here thinks the Americans will try and replace the revolution," said one young Iranian.

One reason many here believe the militants seized the 50 American hostages in the U.S. Embassy last November was the fear that the shah's trip to America had nothing to do with his medical condition. Instead many here believe, it was a way to arrange a clandestine meeting among him, his old generals and United States military and intelligence authorities to plan a replay of the 1953 coup.

Such fears, never far under the surface, intensified here after America's abortiave April 24 attempt to rescue the hostages. Hard-liners among the mullahs running the country charge that the United States intends to stage an internal coup through its secret supporters in the Army, who were blamed for letting the American aircraft land on Iranian territory.

While the official government line is that the failed rescue attempt proves that America is a paper tiger militarily, thoughtful Iranians are worried about the country's poor air defenses that allowed American helicopters and transport planes to penetrate so deeply into this country.

The fears of another attack also are fueled by reports, such as the one carried 10 days ago in The Washington Post from Paris, that former members of the shah's governmet still command support in the Army and are looking to take over the country again.

Even President Abol Hassan Bani-Sadr contributed to the mood of suspicion when he said the United States had infiltrated 96 Americans and 16 Iranians, who had lived in the United States for long periods of time, to carry out sabotage operations here.

It took a statement from Khomeini to calm these fears. He said a coup is impossible because the people in the armed forces support the Islamic revolution. "You cannot make a coup with a tiny number of opponents," he said.

There are even reports that some of the shah's former generals have visited Iraq and from there have entered Kurdistan to help the anti-government fighters.

The fears of further American military action are so great that some responsible Iranians -- people who played a major part in the Islamic revolution that brought Khomeini to power -- talk privately of getting some guarantees from the United States that it will not try to topple the government or attack the country once the hostages are let go.

While these fears appear silly to Americans, who see the intransigence of the Iranian authorities as violating both Islamic and international law in holding the hostages for more than 200 days, they are widely believed here and most diplomats think they are a force that must be reckoned with in any attempt to get the American diplomats freed.

The radio broadcasts, which are being widely talked about among Iranians who learn of them through word of mouth while shopping and walking through the parks, are viewed by diplomats here as a deterrent to any quick release of the hostages.