So I bought this cheapo FM transmitter off eBay and I haven't got a clue on how to use it:
LCD FM Transmitter Car Charger 4 iPhone iPhone 3G iPod - eBay (item 190387654039 end time Sep-05-10 18:37:28 PDT)

I turn the transmitter to an open frequency, I tune my radio to that frequency, I play a song on my iPhone 3G... and my radio is quiet. I only hear the music out of my iPhone's speakers, not the cars.

What did I do wrong?