An FM modulator allows you to be able to hook up an auxiliary device (such as an iPod or satellite radio receiver) through a car's regular radio channels. FM modulators come in many shapes and sizes and have a wide price range.
FM modulators come in two forms: wireless and hard-wired. A wireless FM modulator (also referred to as an FM Transmitter) plugs a listening device straight into your car's cigarette lighter socket. The wireless FM modulator then broadcasts a weak, low-range signal so your car's radio can pick it up and play it. A hard-wired FM modulator is connected via wires directly to your car's antenna unit, creating a solid connection for the listening device.
Pros and Cons
The wireless and hard-wired FM modulators have pros and cons. For instance, a wireless FM modulator is far cheaper but it has a weak connection to the radio and poor sound quality results from outside radio interference. A hard-wired FM modulator will have a clean signal almost all the time; however, it costs more because (to ensure proper installation quality) it must be professionally installed.
An FM modulator is a beneficial tool. No longer do you need CDs or cassettes in your car. In fact, you never have to listen to the radio anymore. You can simply plug your iPod or other listening device straight into your car's cigarette lighter socket and play your own music. Of course, depending on how much you are willing to spend determines the sound quality an FM modulator will provide.