AIR Mathura

7/27/2019 AIR Mathura

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TRAINING PRESENTATION ON

Submitted to :Prof. H.S. SIYAN

Department Of Electronics & Communication

Presented By :ROHIT NARAIN

ECE-D

AJAY KUMAR GARG ENGINEERING COLLEGE

STUDIO CHAIN & FM TRANSMITTERS

ALL INDIA RADIO(AIR) & DOORDARSHAN,MATHURA(U.P.)


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CONTENTS

IntroductionHistory and present scenarioMethodology of Radio TransmissionStudy of Studio ChainFM Modulators/Demodulators


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INTRODUCTION TO A.I.R

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A.I.R is one of the largest radio networks inthe world.

A national service planned, developed andoperated by the Prasar Bharati BroadcastingCorporation of India

All India Radio, Mathura was established at29 January 1967 .

The Satellite Earth station was established at

21st March,1944.


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HISTORY AND PRESENT SCENERIO

The first radio program in India was broadcast by the Radio Clubof Mumbai in June 1923 .

In 1926 the private Indian Broadcasting Company (IBC) wasgranted permission to operate two radio stations; the Bombay

station was inaugurated on July 23, 1927, the Calcutta stationfollowed on August 26, 1927.

The introduction of the commercial channel Vividh Bharti inOctober 1957 increased the interest and popularity of radio.


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METHODOLOGY OF RADIO TRANSMISSION

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BASEBAND SIGNAL MODULATED SIGNAL IS SENT


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STUDY OF STUDIO CHAIN IN ALL INDIA RADIO

Studio center Broadcast station Mixing Control room Recording room

STUDIO CENTER CONSISTS OF VARIOUS TYPES OF MICROPHONESDEPENDING UPON THEIR USE:

CONDENSOR TYPERIBBON TYPEDYNAMIC TYPE


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CLASSIFICATION OF MICROPHONES

CONDENSOR TYPE

Simplest of all the microphones.

work by converting signals caused by acousticenergy to electrical energy resulting in astronger signal.

Use energy from battery supply.RIBBON TYPE

a velocity microphone , which means thatsuch usually respond to the velocity of the air that is produced by the sound .

Ribbon microphones operate bysuspending loosely small elements in amagnetic field that is quite strong .


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DYNAMIC TYPE

These are the kind of microphonesthat generate signals by a conductor which is in magnetic field being inmotion.

FREQUENCY RESPONSE OF MICROPHONE DEPENDS UPON:

Direction of Arrival of Sound.DirectivityDistance between the source and the microphone.


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BROADCASTING HUB

AIR has now accomodated FM Transmitters & Receivers as they aremore clear,good quality Listening,Low interference.

AIR in Mathura has 26 transmitters of 1 KW each. These are AMTransmitters operating at 1584Khz.

BLOCK DIAGRAM OF FM TRANSMITTERDescription can beexplained into 2 phases:-

PHASE-1PHASE-2


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PHASE-1

The L and R audio signals are converted intothe stereo signal by a stereo coder. The stereosignal, also called the MULTIPLEXED (MPX)signal.

This frequency modulates the VHF oscillator which is a voltage controlled oscillator (VCO)of the phase locked loop (PLL).

The PLL is an automatic frequency control (AFC)system in the FM transmitter .

Phase of the VHF oscillator is compared withthat of a reference crystal oscillator operatingat 10 MHz the frequency of the referenceoscillator is divided by 1/1000 with the help of three decade counters in cascade to bring it

down to the audio range (10khz)


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PHASE-2

The phases of the outputs from the twofrequency dividers are then compared ina phase comparator.

The resultant error voltage is amplified,rectified and filtered to get a DC error voltage of positive or negative polaritywhich corrects and drift in the VHFoscillator frequency.

The operating frequency and the variablefactor N are synthesized with the help of digital frequency synthesis techniques.

The FM signal obtained at the output of VHF oscillator is then amplified in a VHFPower Amplifier with an output power of 1.5 kW


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ANTENNA SYSTEM OF TRANSMITTER


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RECEIVER SIDE: RADIO NETWORKING TERMINAL

RNT acts as a groundterminal for satellite signalreception.

Parabolic Dish Antenna :Circular polarization of INSAT broadcast is used as

it does not require anyadjustment of feed or polarization matching.

Low Noise Amplifier (LNA) :It contains two LNA PCBs tohave 100% redundancy.

Front end converter : It hasalso got two chains for redundancy. Any one chaincan be selected by RFswitch provided at its input


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RECORDING

RECORDING is done in AllIndia Radio through magnetictapes.

Magnetic recording is madepossible due to magnetismremaining behind after themagnetizing force is removed.

The magnetic material used inrecording is magnetic oxide of iron Fe 2O 3 and Fe 2O 4 .This ismixed with suitable adhesives,plasticizers, fillers etc. andapplied in the form of anextremely smooth, even andthin coating (0.4 to 0.6 mils) onto a PVC backing (1.0 to 1.5mils thick ).


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AIR Mathura

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