A personal FM transmitter is a low-power FM radio transmitter that broadcasts signals from portable audio devices, such as MP3 players, onto a standard FM radio. Among these transmitters, some plug into the headphone jack of the device, some through wireless Bluetooth Bluetooth technology (e.g., with a Bluetooth FM transmitter), and then broadcast the signal through the FM broadcast band frequency so that any radio nearby can receive it. This allows portable audio devices to take advantage of louder or better sound quality from home audio systems or automotive stereo systems without the need for a wired connection. They are commonly used in cars, but may also be used in fixed locations.
Due to national regulatory restrictions, these transmitters have low power and short service distances, depending on the quality of the receiver, obstacles, and altitude.
Test requirements of national regulations
Note: Most of the other regions refer to the requirements of European standards, and some regions may have special requirements.
Test site and equipment requirements
FM transmitter is generally tested in a 3-meter semi-electric wave anechoic chamber, using an audio analyzer to provide audio signals to the product, and measuring the product's main wave power, frequency offset, bandwidth, transmission spurs, transmission time and other test items with the measurement receiver.