Introduction :
The master oscillator generates a stable sub harmonic carrier frequency (i.e. the fraction of a desired carrier frequency). This stable sub-harmonic oscillation is generated by using a crystal oscillator and then frequency is raised to the desired value by harmonic generator. The carrier frequency ought to be very stable. Any change in the master oscillator frequency will cause interference with other transmitting stations and receiver will accept programmes from more than one transmitter.
Buffer Amplifier:-
This is a tuned amplifier providing high input impedance at the master oscillator frequency. Any variation in load current does not affect the master oscillator due to this high input impedance of buffer amplifier at the operating frequency of the master oscillator. Thus, buffer amplifier isolates the MO from the succeeding stages, so that the loading effect may not change the frequency of the master oscillator.
Harmonic Generator:-
It is an electronic circuit that generates harmonics of its input frequency. The principle of harmonic generation is the same as that of a non-linear modulator. When a signal is applied to a non-linear circuit, it generates harmonics of input frequency. The desired harmonic is selected by a properly tuned circuit. The circuit uses a class C tuned amplifier.
One or more stages of a class C tuned amplifier are used to increase the power level of a carrier signal to provide a large drive to the modulated class C amplifier. The output of the harmonic generator provides a low power carrier signal. This power is amplified to raise power to desired level to drive the final amplifier stage. This stage is termed as driver amplifier or intermediate power amplifier.
Modulation system:-
The collector modulation circuit is used for modulation in high power transmitters. The modulating amplifier is a class A, or class B amplifier amplifying the base band signal.
Feeder and Antenna:-
The transmitter power is fed to a transmitting antenna for effective radiation. The length of the antenna (a conductor) should be of the order of the wavelength for effective radiation. The antenna is normally located at a distance from the transmitter and hence power from the transmitter is fed to the antenna through a properly designed transmission line called feeder.
Block diagram of AM transmitter is shown below.
Parts of am Transmitter:
Master Oscillator:-The master oscillator generates a stable sub harmonic carrier frequency (i.e. the fraction of a desired carrier frequency). This stable sub-harmonic oscillation is generated by using a crystal oscillator and then frequency is raised to the desired value by harmonic generator. The carrier frequency ought to be very stable. Any change in the master oscillator frequency will cause interference with other transmitting stations and receiver will accept programmes from more than one transmitter.
Buffer Amplifier:-
This is a tuned amplifier providing high input impedance at the master oscillator frequency. Any variation in load current does not affect the master oscillator due to this high input impedance of buffer amplifier at the operating frequency of the master oscillator. Thus, buffer amplifier isolates the MO from the succeeding stages, so that the loading effect may not change the frequency of the master oscillator.
Harmonic Generator:-
It is an electronic circuit that generates harmonics of its input frequency. The principle of harmonic generation is the same as that of a non-linear modulator. When a signal is applied to a non-linear circuit, it generates harmonics of input frequency. The desired harmonic is selected by a properly tuned circuit. The circuit uses a class C tuned amplifier.
Parts of am Transmitter:
Driver Amplifier or Intermediate Power Amplifier:-One or more stages of a class C tuned amplifier are used to increase the power level of a carrier signal to provide a large drive to the modulated class C amplifier. The output of the harmonic generator provides a low power carrier signal. This power is amplified to raise power to desired level to drive the final amplifier stage. This stage is termed as driver amplifier or intermediate power amplifier.
Modulation system:-
The collector modulation circuit is used for modulation in high power transmitters. The modulating amplifier is a class A, or class B amplifier amplifying the base band signal.
Feeder and Antenna:-
The transmitter power is fed to a transmitting antenna for effective radiation. The length of the antenna (a conductor) should be of the order of the wavelength for effective radiation. The antenna is normally located at a distance from the transmitter and hence power from the transmitter is fed to the antenna through a properly designed transmission line called feeder.
I like to share this what is amplitude modulation with you all through my article.
Check my best blog Extraction of organic compounds.
No comments:
Post a Comment