Sitting in his son's bedroom, Allan Kamerow's could hear the gunfire. It was muffled, like machine guns behind a wall of pillows. But the staccato sound was amazingly clear for having traveled 5,100 miles.

"I just happened to be pointing my antenna toward Africa," said Kamerow, an Alexandria attorney and a ham radio operator. "Suddenly I was eavesdropping on a revolution."

The revolution was in Liberia, a West African country established in 1847 by freed American slaves. Two weeks ago the old order was violently overthrown. In the coup, Liberian President William R. Tolbert and 27 members of his family and political supporters were executed.

For Americans in Liberia, the overthrow led to hours of anxiety. Against a background of gunfire, they waited uncertainly for the new order to define its relationship to them. For their relatives and friends in this country, the uncertainty was considerably longer. Rumors crossed the Atlantic faster than the real news Women had been abducted. American citizens were under arrest. Officials communication was cut off.

The only reliable contact with Liberia came via a ham radio station operated by Baptist missionaries in Monrovia. It was that station Kamerow picked up on his radio Monday evening, April 14. During the next three days, with time off for work and sleep, Kamerow served as a local information center.

"They (the missionaries) were looking for people in different parts of the country to carry messages for them," said Kamerow, who remained turned into the station from 8 p.m. April 14 until 3 a.m. April 15, slept for three hours, then tuned in again. "I don't know how many phone calls I made. I was really hyped up."

Along with other ham operators in the area, Kamerow helped spread the calming word to worried area residents. By Thursday, April 16, when the situation in Liberia was stabilizing, Kamerow lost contact with the missionaries.

"I haven't been able to get them since," Kamerow said last week as he played with the dials of his compact radio setup the second floor of his Alexandria home.

For Kamerow, who has had his ham radio license just three months, the Liberian affair was a heady initiation into airwave assistance. But it was only the latest episode of aid provided by local ham radio operators, a group that numbers approximately 7,000 in the metopolitan area.

In 1968 an Annapolis ham, John Hutchins, intercepted an appeal from Brazil for anti-coagulant drugs needed for an emergency cerebral hemorhage operation. Within three hours the drugs were on a plane for Brazil.

In 1972 Richard Hayman, of Potomac, picked up an SOS from Ecuador asking for special surgical mesh needed to save the life of a 6-month-old boy. Hayman relayed the message to Holy Cross Hospital in Silver Spring, which supplied the mesh and helped save the infant's life.

Last year Lee Winde, of Laurel, and Dick Price, of Potomac, suddenly found themselves listening to news of the capture of the American embassy in Tehran and, like Kamerow, helped relay information to families of the 53 hostages. Since then, however, the few friendly ham operators in Iran have been able to offer little useful information, say local amateur operators.

Local ham operators have contacted sailors in the Antarctica, served as conduits between Alaska and Argentina during disaster and once even helped a Georgetown University graduate get a PhD. Since her professor was in South America she defended her thesis by radio.

"During the severe hurricanes last summer in Central America, amateurs (hams) organized a network to report positions of the hurricane to Carribean island stations," says Steve Glickstein, president of the Northern Virginia FM Association, which includes 682 amateur radio operators.

Amateur radio enthusiasts take pride in their record of global assistance. They also take pains to point out that the ham radio crowd is very different from Citizen Band (CB) "good buddies," whom they generally regard as airwave pollutants.

Sen. Barry Goldwater (R-Ariz.), a dedicated ham, said in 1977 that many CB enthusiasts "abused the system" and often used profanity on the air. He further complained that prostitutes around the country had been heard soliciting over the air.

Goldwater's complaints were in response to a column written that year by Jack Anderson, who harrumphed that the approximately 300,000 hams then operating in this country had 100 times more airspace than the 9 million CB enthusiasts.

That issue is no longer being debated, but not because the proportion of air space has changed. What has changed, dramatically, is the popularity of CB radio. While licensed ham operators now number almost 400,000, CB clubs have been decimated.

"I couldn't feed a mouse on the income from CB nowadays," says Lou Raines, owner of what used to be called Universal CB in Alexandria, which was one of the largest CB supply shops in Northern Virginia. The company is now called Metro Antenna and TV Specialists. "I'd say (CB) business is off 95 percent at least. We've about gotten completely out of it and diversified into other fields."

Raines gives the same reason for the CB crash as former CBers who switched to ham radio. Getting a CB radio was too easy. As a result, the airwaves became crowded and rudeness prevailed.

"A lot of average people who went into CB were disappointed with what they found," said Glickstein.

To operate ham radio, on the other hand, a license has to be earned by passing a battery of tests. Operators must be able to send at least 13 words a minute by Morse Code and be conversant with vectors, electronic theory and advanced math.

"My kids taught me algebra. My newphew helped me with electronics . . . and I flunked," said Kamerow, who took the final exam three times before passing it. Much of what he learned he will never have to use. The stringent exams are meant to protect the airwaves, says Kamerow, from abuse.

Now that the Liberian drama has passed, Kamerow has returned to more normal conversations with ham operators around the world. He has chatted with English-speaking hams from Tokyo to Moscow.

"This morning I got up early, I tuned in Europe and had delightful conversation with a fellow in Italy who runs a wood shop. Yesterday I talked to a fella in Japan . . ..," said Kamerow last week. "There's a lot of fantasy involved."

And sometimes the sound of gunfire.