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What is an In-Car FM Modulator?

What is an In-Car FM Modulator?


An in-car FM modulator is just a radio frequency modulator that is specifically designed for use in car audio systems. Radio frequency modulators are essentially just workaround devices that were originally designed to allow external components to be hooked up to televisions and home radios.


Since both televisions and home radios were originally designed to accept only RF inputs from antennas, RF modulators work by adding an audio or video signal, or even both, to a carrier wave, which can then be processed by a TV set or a head unit just as if it had been received via an over the air broadcast.


FM modulators are largely unnecessary in home theater setups today unless you are dealing with extremely old equipment. Modern televisions and audio receivers are built from the ground up with HDMI, RCA, optical, and other connections in mind.


Car radios are another matter, and basic car radios, even brand new ones, often lack any way to connect external equipment. Since the one thing just about every car radio does have is an FM radio, that opens the door for FM modulators.


Car FM Modulators and FM Transmitters

While car FM modulators and transmitters are very similar, there is one key difference in the way that the head unit receives the signal. Due to laws that restrict the power of unlicensed radio transmitters, car FM transmitters have to be very low power. They’re strong enough to transmit the few feet that typically separate them from the car antenna, but it’s easy for such a weak signal to be drowned out in an area where there aren’t any dead spaces on the FM dial.


Since car FM modulators pipe the signal directly into the head unit, there’s less of a chance for interference. These devices can still suffer from interference, and they usually can’t match the audio quality of an auxiliary port, but they are a good option for head units that don’t have auxiliary ports.