Requesting Songs on The Radio

wassup yall! well my question is that when i make requests on da radio they haven't been played. i have requested a tight song by the ying yang twins ft. pitbull called "shake" several times and has never been played. is it because that song doesn't have enough requests? in general how many requests are needed to get a song played on the air especially if it's a brand new song? the funny thing is i hear the song "shake" on other hip hop stations. i don't know whether my requests are being ignored, the station always says that they'll play anything you want to here. so big von man please help a brother out and tell me how this request thing works. holla back.