The FM modulator or FM transmitter is a device used to play your plug-and-play Satellite radio receiver through your vehicle's FM stereo. FM transmitters can also be used to play other digital audio devices like iPods, CD and MD players.
Normally second choice to an audio cassette adaptor because of sound quality, the FM modulator is still a very quick and simple way to get your plug-and-play Satellite radio receiver working in your vehicle.
Although sometimes only used if all else fails, the FM modulator at least provides an option for listeners who not audiophiles, want an easy way to hook up their receiver, or simply do not have a built-in cassette player in their vehicle.
Enough degrading these devices; there are probably thousands of Satellite radio listeners out there who will tell you that they experience good reception using an FM modulator. However, there is no doubt about it, an FM modulator, if used, can and will on occasions degrade the quality of audio output from your plug-and-play Satellite radio receiver.
An FM modulator converts the audio signal from the plug-and-play receiver into an FM signal, which is then transmitted over an unused FM frequency or station selected by the listener. The limitations of the FM frequency band mean this in no way represents what the signal actually sounds like.
There are two types of modulator available; wireless and hardwired.
The wireless modulator is built-in to a power adaptor that plugs into the cigarette lighter socket, the docking station or cradle that houses the plug-and-play receiver, or, more recently, the plug-and-play receiver itself. The receiver's audio output is transmitted over the air to an unused FM frequency.
The wireless modulator is convenient, easy to install and configure, but broadcasts only a very short-range signal prone to fading and with interference; comparatively weaker compared to a hardwired modulator.
The hardwired modulator is placed in between the vehicle's stereo unit and antenna. The modulator connects directly into the stereo's FM antenna socket to provide a better frequency response and a signal with less interference that is less lightly to fade.
It is recommended that a hardwired modulator be installed professionally, as it requires a connection to the antenna socket on the rear of the vehicle's stereo and to the electrical system, all located behind the dashboard.
The amount of interference, static and fading you experience, using either of these devices, depends on where you are geographically located in the US, quality of the in-built tuner or broadcast and the type of modulator installed in your vehicle.
For example, somebody living in a major metropolitan area, using a wireless modulator, will no doubt experience poor reception along with the frequent and often debilitating interference from other radio stations.
With regard to sound quality, the wireless modulator rests at the bottom of the pile with the hardwired version above it. However, depending on circumstances, hardwired modulators can be as good as cassette adaptors if not better.
