Zk50group07 Frequency Modulation (FM) Application

FM Transmitter

Frequency modulation (FM) can be defined as a technique that conveys information over carrier wave by varying its instantaneous frequency. FM is widely used in telecommunications and signal processing especially broadcasting of music and speech, in two way- radio system, in magnetic tape recording system and some video transmission system. In order to use FM as the medium to transmit information, we need an equipment that called FM transmitter. The FM Transmitter is designed to transmit any audio to any FM Receiver. We can transmit satellite audio to any receiver or car stereo, transmit Internet audio from your computer to your portable radio, and also transmit audio from your MP3 player to your home stereo or car.

An FM transmitter is a portable device that plugs into the headphone jack or proprietary output port of a portable audio or video device, such as a portable media player, CD player, or satellite radio system. The sound is then broadcast through the transmitter, and plays through an FM broadcast band frequency. Purposes for an FM transmitter include playing music from a device through a car stereo, or any radio.
The FM-transmitter plugs into the audio output of audio devices and converts the audio output into an FM radio signal, which can then be picked up by appliances such as car or portable radios. Most devices on the market typically have a short range of up to 30 feet (9 meters) with any average radio (up to about 75 feet (23 meters) with a very good radio under perfect conditions) and can broadcast on any FMfrequency from 76.0 to 108.0 MHz
This FM Transmitter transmits high-fidelity audio from any audio source such as Computer, TV, or CD player to any FM radio receiver. Superior engineering and construction techniques were used to bring you the highest quality FM transmitter possible. Never before has this level of performance been available at such a low price. Digital tuning and Phase Locked Loop technology have been incorporated for full FM band frequency coverage, with stability and superb audio quality.

To transmit audio from the FM Transmitter, it is best to find a clear FM frequency that is not being broadcast on and free from interference.

1) Start with a radio and scan through the entire FM band (using adigital radio will be easiest). We are looking for the largest gap in between stations, so we find a gap, select a frequency located somewhere in the middle. Example: There are no stations broadcasting between 90.1 - 93.5, select 91.5. Preferably there won’t be a station broadcasting on either side of the frequency that we have selected.

2) Turn the power on of FM Transmitter. Use the up or down tuning arrows to
select the same frequency as on our radio. Hold the arrows down for faster tuning.

3) With the FM Transmitter plugged into the radio or other audio source, make sure we have adequate volume. The red LED light indicates there is too much volume. Adjust the input level control on the side of the unit or adjust the volume of audio source until the light goes off. Futhermore, too much audio may cause distortion for FM Transmitter.

If we are using a needle and dial radio, this transmitter must to tune to the general vicinity. If this frequency not match exactly, we may need to fine tune your radio to the frequency. If we have a second radio to plug the FM Transmitter into, we can tune the FM Transmitter until we can get the clearest signal on your first radio. This FM Transmitter also has itself antenna orientation. We can start with the antenna straight up and fully extended then orientate the antenna to help transmit the signal a certain direction.

The relatively low power output of FM transmitters sometimes makes it unsuitable for use in some large urban areas because of the number of other radio signals. This is compounded by the fact that strong FM signals can bleed over into neighboring frequencies making the frequencies unusable with the transmitter. Removing a car's radio antenna has been found to significantly improve transmitter reception.

Some models which connect via ports other than the headphone jack have no means of controlling the volume, which can force the sound to transmit out from the device harshly (causing over modulation, audio distortion and possible radio interference), or too low. In theory a device could use an automatic level control or audio limiter circuit to overcome this problem.

In addition to make this FM transmitter work more better, we must located this device at optimum place as usually away from other electronic devices and objects. The higher the transmitter is located the better. The transmitter can be helped by placing it on something that will act as a ground plane like a metal filing cabinet or a refrigerator. Try moving it around for best performance. More than that, range is subject to many variables, including obstructions such as walls and FM signal overload in your area. The range of the FM Transmitter is between 30 and 75 feet, line of sight with no obstructions.