BERKELEY, Calif.-For most of his life, Stephen Dunifer did not hesitate to speak out or become involved in causes, from saving redwoods to protesting the Persian Gulf war. But the only cause that has put him in the limelight is his current one: the battle to open the nation's airwaves to small, low-power stations like his Free Radio Berkeley.

His fight began on a night four years ago when he hiked into the Berkeley hills with a radio transmitter tucked in his backpack and sent his voice out over the local airwaves. The battle has since moved to federal court, where Dunifer is challenging Federal Communications Commission regulations that set a minimum transmission power standard of 100 watts for any radio station with a broadcast license.

For two generations, Berkeley has been synonymous with rebellion against the status quo, with contrarianÑnot to mention utopian -- thinking. Dunifer's notion that anyone with a transmitter should be able to start a radio station fits the egalitarian tenor of the town. The bearded, genial Dunifer considers his Free Radio Berkeley broadcasts an exercise in free speech and a galvanizing force for listeners. The station's mix of news, music, and political commentary in half a dozen languages, he says, gives a voice to segments of the area ignored by larger stations.

But by operating it, he is ignoring federal rules. As the FCC continues its efforts to legally enjoin him from broadcasting, the fight that the 46-year-old self-taught electronics engineer and computer-system designer is waging has become a cause celebre for many of the perhaps 1,000 unlicensed broadcasters nationwide. Many of them, in fact, are his customers; he also sells the equipment needed to start a low-power station.

In their 1993 rebuttal to the FCC's attempt to fine Dunifer $20,000, his lawyers wrote that "the fundamental problem is that the FCC has not provided procedures by which micro radio broadcasters can become licensed. ... ." But if Dunifer's advocates see him as a free-speech crusader and the Johnny Appleseed of low-power radio, the FCC, the legal guardian of the common property of the airwaves, sees him as a radio "pirate" who is breaking the law, disrupting licensed broadcasters, and posing a threat to public safety.

The heart of Dunifer's argument is that the FCC's regulations, particularly a 1978 rule requiring an applicant for a radio license to use a transmitter with a minimum power of 100 watts, are based on outmoded technological assumptions and set an insurmountable economic barrier for many would-be broadcasters.

In one filing, Dunifer's lawyers wrote: "The cost of owning and operating a radio station has skyrocketed into the hundreds of thousands and even million-dollar range," effectively limiting participation in the broadcast media to large corporations only. Since 1993, when Dunifer's court battle with the FCC began, he has achieved a partial victory. Judge Claudia Wilkin refused in November to grant an injunction sought by the FCC that would have shut Dunifer's station down pending arguments on his contention that existing rules amount to an unconstitutional restraint on free speech.

But as far as the FCC is concerned, Dunifer is flouting rules that other broadcasters must live with. In a telephone interview last week, William E. Kennard, the new chairman of the FCC, said that the commission had studied proposals to license small radio stations, "and I think they rejected that approach because of interference concerns."

"It's a terrible safety problem," Kennard said. "Some of these unlicensed broadcasters have chosen bands adjacent to air traffic control channels. We just can't allow a situation where you have illegal broadcasters disrupting communications between pilots and control towers." That argument means little to Dunifer. "The air-to-ground frequencies are 118 to 135 megahertz," he said. "There would be no reason for anyone operating in those bands, because no one will be able to hear them." Commercial FM radio operates between 88 and 108 megahertz.

Dunifer is not the only pirate broadcaster in the FCC's sights. The commission's push against low-power broadcasters has taken two such stations off the air in the last two months: Radio Free Allston, a noncommercial low-power station in the Boston area, which the agency shut down on Oct. 28, and "Tampa's Party Pirate" in Florida, which was closed last month. In New York City, the Steal This Radio collective, at 88.7 FM, started its station in 1995 on the Lower East Side with an antenna built from plumbing supplies. It remains on the air. Such broadcasters, Dunifer argues, serve a vital function in their communities, giving more voices a chance to be heard. The FCC, he declares, should accommodate them. "This is an important case because it shows the really corrupt nature of broadcast policy," said Robert W. McChesney, a scholar who has written several books on mass media. "The reality is that the commercial broadcast lobby is the single most powerful lobby in the country. Given their immense power, it's virtually impossible for any public participation, so the laws are simply undemocratic and corrupt."

In the spring of 1993, the FCC, perhaps acting on a complaint, began monitoring Free Radio Berkeley broadcasts, then sent Dunifer a notice that he would be fined $20,000. Dunifer's lawyers contested the fine, leading the FCC to seek an injunction against his broadcasts. Dunifer was gleeful. "We've gotten our fondest wish, which is to be in federal court," he said recently. "This was being done basically as a free-speech statement and a challenge to their regulatory and statutory structure."

The focus of his challenge, currently before the Federal District Court for the Northern District of California, is a 1978 FCC regulation limiting the award of new broadcast licenses to stations operating at a minimum of 100 watts. The rule was adopted in an effort to eliminate clutter and overlapping signals, but it also had the effect of raising the price of entry for broadcasters.

"This is the moment for this kind of thing to come together because the technology has made it possible," said Ron Sakolsky, a public policy professor at the University of Illinois. "If you get an FCC license, you have to initially invest $50,000 to $100,000," he said. "Now, it's possible to do it for a much smaller cost, and people are saying, 'Why can't we go on the air?' "

For those in a hurry to get their soapbox on the air, Dunifer sells a package for $595 that includes equipment for a half-watt station. It does not include audio gear, but "$1,500 can get you on the air," he said. Half a watt of power sends a signal strong enough to cover about half a mile.

Dunifer said he emphasized with all would-be broadcasters the importance of taking every precaution to prevent interference with other signals.

Not surprisingly, broadcasters who have paid their license fees and are protective of the clarity of their signals are working with the FCC to shut down low-power stations. The National Association of Broadcasters says the number of unlicensed micro-broadcasters has been growing as the price of broadcasting equipment drops.

"We want to make sure unlicensed broadcasters and their illegal activities won't be tolerated," said John Earnhardt, a spokesman for the association, which has pushed the FCC to step up enforcement.

Still, in his interview, Kennard emphasized that he was open to changing the face of the radio spectrum.