The main advantages of FM over AM are:

The equipment for long distance communication is very important. Communication takes place either through heliograph signaling using a flashing mirror, electrical lamps, spot lights, colored disks, etc., or it is accomplished electrically by radio or by wires within the confined areas of the space station.

long distance communication. Definition English: Telephone and telegraph service over wire and radio systems between correspondents located at great (virtually unlimited) distances from each other.

• Improved signal to noise ratio (about 25dB) w.r.t. to man made interference.
• Smaller geographical interference between neighboring stations.
• Less radiated power.
• Well defined service areas for given transmitter power.

Frequency modulation is widely used for FM radio broadcasting. It is also used in telemetry, radar, seismic prospecting, and monitoring newborns for seizures via EEG, two-way radio systems, sound synthesis, magnetic tape-recording systems and some video-transmission systems.

There are two different types of frequency modulation used in telecommunications: analog frequency modulation and digital frequency modulation.

Noise is a form of amplitude variation and a FM receiver will reject such noise signals. (ii)The operating range is quite large. (iii) The efficiency of transmission is very high. (i) A much wider channel is required by FM.

FM uses a higher frequency range and a bigger bandwidth than AM. Each FM station is allocated 150 kHz of bandwidth, which is 15 times that of an AM station. This means that an FM station can transmit 15 times as much information as an AM station and explains why music sounds so much better on FM.

1. In Fm receivers the noise can be reduced by increasing the frequency deviation and hence Fm reception is immune to noise as compared to AM reception, 2.Fm transmitters are highly efficient than AM transmitters as in Am transmission most of the power goes waste in the transmitted carrier.

Disadvantages of FM over AM are FM systems have a much wider bandwidth than AM systems and therefore more prone to selective fading. FM transmitter and receiver require booster circuits as they have poorer signal to noise ratio at high audio frequencies.

Overmodulation is the condition that prevails in telecommunication when the instantaneous level of the modulating signal exceeds the value necessary to produce 100% modulation of the carrier. Overmodulation results in spurious emissions by the modulated carrier, and distortion of the recovered modulating signal.

AM Detector. The detection of AM radio signals is a diode application. The modulated AM carrier wave is received by the antenna of the radio receiver and is rectified by the action of a detector diode.

Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. A modem is an equipment that performs both modulation and demodulation.

Amplitude modulation detectors

• Envelope detector.
• Product detector.
• Phase detector.
• The Foster-Seeley discriminator.
• Ratio detector.
• Quadrature detector.
• Other FM detectors.