By Daniel Emery
Technology reporter, BBC News website
DJ Paul Edwards: The listeners, they appreciate what I do, I don't really look at it as illegal
Drive through any big city, turn on your car radio, and the odds are that you will stumble across a pirate radio station.
For some they are the sound of the street and a way of getting new music out to the masses. For others, they are a nuisance that can drown out legitimate radio stations.
It is 1000 on a Monday morning. In a property in south London, Paul Edwards, a DJ for Supreme Dance FM, is filling the airways with house, funk and electronic music, with its listeners texting or e-mailing the show. The DJ name checks each of them with a 'shout'.
Ben Ando goes with police raiding a suspected pirate radio station
For the audience, it is a way of hearing new music before it is even in the shops, let alone before it gets played on commercial radio stations. For the authorities, the pirate station is breaching the 2003 Communications Act.
It is thought there are now more than 150 pirate radio stations operating across the UK, half of which operate in London and the South East of England.
Turn on, tune in
Many stations serve a particular genre of music, or demographic, with clear transmission localised to a few square miles.
Ray Gambeno, a record producer from south London, told the BBC that pirate radio gave up and coming artists the opportunity for exposure and airplay that would be hard, if not impossible, to get on commercial radio stations.
"Pirate Radio stations are able to play what they want to play.
"With a legal radio station, they have a set play list, so you're not going to get to hear what you want to hear."
Record producer Ray Gambeno defends pirate radio
Last week, officers from the Metropolitan Police and officials from Ofcom pulled the plug on one alleged pirate radio station in north London.
Ofcom had received more than 100 complaints that a transmission had been interfering with the commercial broadcaster LBC and the regulator was out to "put them out of business".
The operation was supposed to get under way just after 1400 GMT, as soon as the adverts on the station had finished, although it was 40 minutes before the last advert was over and a new DJ started his set.
It did not last long.
Officers stormed a business centre in Tottenham and, after some initial confusion, located a radio studio. Five people were arrested, music and broadcast equipment was seized and a considerable amount of money was found on the premises.
Technicians on the roof, examining a microwave link to a remote transmitter, also found a cable linking to a second alleged pirate station, that while not transmitting, contained radio equipment which officials also seized.An unexpected bonus for the officers on the raid.
One of the criticisms levelled at pirate radio stations is that they are just in it for the money.
Not all bad
There are some stations who seek to serve the community
However, Ofcom's head of investigations, Paul Mercer, told the BBC that while some stations were purely driven by profit that was not always the case.
"As we tune into illegal broadcast radio stations, we become acutely aware of some stations that carry lots of advertisements of night club events. And those that never seem to have any advertisements
"We take from that there are some stations who seek to serve the community, rather than generate some of the vast sums of money that can be generated through pirate radio."
So what motivates people to set up and play on a pirate radio station?
Steve, who manages the pirate radio station Ice Cold FM, told the BBC that most people did it for the love of music.
"I still have to hold down a full time job. If I was raking it in, I wouldn't be getting up for work at seven every morning."
Certainly the people working at Supreme Dance FM appear to be doing it for the love of music, rather than trying to make a fast buck. The station is remarkably free of adverts and the owners say they do their best to ensure the station keeps a clean signal which does not cause any interference.
While those involved in pirate radio acknowledge that Ofcom's job is to enforce the law, many are blase about the illegality of their broadcasts.
Ofcom raided 43 pirate radio stations in 2008
Speaking to the BBC, DJ Solution - a pirate radio DJ from west London - said that the illegality had never bothered him.
"I'm not harming anyone, I'm just playing my music. We're not swearing, we're not promoting guns or selling drugs."
Ray Gambeno said that many in pirate radio would want to go legal, but as long as it did not compromise the music that they wanted to play.
"They must feel bad about it, because they must wake up in the morning thinking that not everything they do is completely legitimate."
Of course, there are ways to run a radio station and not fall foul of the law. One way is to set up as a community radio station.
Steve from Ice Cold FM said that it was difficult to win a community radio station licence.
"I wanted to go legal. We tried to get a community based licence and even went off air for a while.
"But once we looked into it, they wanted us to show that we had £25,000 in sponsorship to prove that we could establish the business for a length of time, which is far more than we would actually need.
"Even to apply costs money and Ofcom can still say no, so it's just not worth the effort."
Another way is to set up as an internet radio station. You don't need a licence; copyright notwithstanding, you can play whatever you like and then stream it all over broadband.
Internet radio is legal and can reach a global audience
Many pirate stations already stream on the internet, but with the majority of their listeners either driving a vehicle, or living in parts of the community where a PC and broadband is an unaffordable luxury, they are unlikely to put an end to their illegal broadcasts.
Paul Edwards explained why, for now, Supreme Dance would continue to broadcast on FM radio.
"Radio is a major part of my life. People can listen to it in their cars, it's great.
"You can always have a radio near you, but with the internet, sometimes you can't get the access to listen to the music when you want and where you want."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.