AM TRANSMITTER

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AM TRANSMITTER In an  AM  ( amplitude modulation )  transmitter  the amplitude (strength) of the carrier wave is varied in proportion to the modulation signal. In an FM (frequency modulation)  transmitter  the frequency of the carrier is varied by the modulation signal. There are two basic configuration for transmitters. High level modulation low level modulation  High level modulation In high power modulation signal,the carrier voltage is modulated at highest power level.the require power level is obtained by class c power amplifier.The block diagram of high level modulation as shown in fig(a). low level modulation In the low level modulation system, the carrier is modulated at low power level and the carrier power is subsequently raised to the desire level in the class B amplifier . transmitters using high power level are widely use at present .The block diagram of high level modulation as shown in fig(b). advantage AM sign
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Frequency division multiplexing (fdm)

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Frequency-division multiplexing (FDM) is a scheme in which numerous signals are combined for transmission on a single communications line or channel. Each signal is assigned a different frequency within the main channel.

Transmitter
Receiver 
     Advantage
•         It does not need synchronization between its transmitter and receiver.
•         Frequency division  multiplexing is simpler and easy demodulation..
•         It is used for analog signals.
•         A large number of signals (channels) can be transmitted simultaneously

Disadvantage

  •  It is suffers problem of cross-talk.
  •  It is used only when a few low speed channels are desired.
  •  Intermodulation distortion takes place.

    Application
•      It is used to public telephones and in cable TV systems.
•      It is used in broad casting.
•      It is used in AM and FM broadcasting.
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