Howard Stern, the expletive-ridden US radio presenter, last week announced he is to quit broadcast radio at the end of 2005 to join Sirius Satellite Radio, the struggling subscription service.

Despite (or more likely because of) his predilection for four-letter words, Stern commands a substantial audience of twelve million listeners daily and his raunchy ranting attracts around $100 million (€81.39m; £.11m) in advertising dollars every year – which will leave quite a hole to fill for his syndicator, Viacom-owned Infinity Broadcasting.

According to the Washington Post, his defection has triggered mild panic among some airwaves owners. They fear that the AM and FM industry will be injured, not only because of the loss of one of its most popular broadcasters, but also because the frequencies may be nearing a point of fiscal no return.

Possibly David J Field, chief executive of Entercom Communications which owns 100 radio stations, was whistling in the dark when he asked rhetorically: "What did it mean to late-night TV when Johnny Carson left? The reality is, that was not the demise of late-night TV."

But what intrigues most observers is Stern's motive for quitting an established medium for one that might yet fall flat on its face. Mucho dollars is obviously one answer; the other is freedom to talk real dirty and cuss to his digestive system's delight without threat of penalty from the Federal Communications Commission.

The FCC has no jurisdiction over the two US satellite radio operators: Sirius and XM, which between them boast a mere 3.1 million paid subscribers, respectively charging $12.95 and $9.95 monthly for access to more than 100 largely commercial-free stations.

The snaring of Stern could transform the fledgling industry, believes Walter Sabo, president of Sabo Media and a consultant to Sirius. "This deal has the potential to turn FM into AM and AM into shortwave," he crowed.

Data sourced from Washington Post Online; additional content by WARC staff