Definitely illegal. If you live in a big city like London or NYC, then I'd worry about getting busted. But if you live in Fuckwitzville, USA then I'd say your chances of getting busted are slim, especially if you broadcast on different frequencies (and aren't interfering) and at different times. If you want to broadcast 5 miles, then I think you'd need a pretty powerful amp, unless you wanna mount a 20 foot antenna on your car. I'd say for about a grand you could get a high quality, powerful amp. Hook that biatch up to your 12v, plug your empeg RCA's into it, rig up an antenna and you're all set. Then go to local businesses and ask if they want to advertise on your new radio station....