36132194 pdf training report prasar bharati new delhi

7/31/2019 36132194 PDF Training Report Prasar Bharati New Delhi

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INDUSTRIAL TRAINING REPORT

Submitted in the Partial Fulfillment for the Award of the Degree Of

Bachelor of TechnologyIn

Electronics and Communication Engineering.NORTH EASTERN REGIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY NIRJULI::791109 ARUNACHAL PRADESH

SUBMITTED To:H. O. D. Electronics and Communication NERIST

SUBMITTED By:RAJUL KUMAR PANDEY DE-09-EC-06 BIRAJ CHITROKAR DE-09-EC-32

31st MAY 20th JULY, 2010


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ACKNOWLEDGEMENT

This report is an outcome of the practical training which I have gone through atPrasar Bharti Doordarshan (Broadcasting Corporation of India) Staff Training Institute (Technical) Kingsway Camp, Delhi - 110009. I would like to express deepsense of gratitude towards Mr. N. A. Khan, Director, STI(T) who permitted us toundergo this training. I would like to express my special thanks to Mr. Deepak Thukral, Dy. Director(Engg.), STI(T) and Mr.Rajesh Chandra, Assistant Director, STI(T) our Training Coordinator, who prepared our training schedule and for helping me in understanding the technical aspects of Broadcasting. It is a great pleasure to express my heart full thanks to the staff of STI (T) who helped me directly or indirectly throughout the successful completion of my training.

(RAJUL KR. PANDEY) & (BIRAJ CHITROKAR)


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PREFACEWith the ongoing revolution in Electronics and Communication where innovations are taking place at the blink of eye, it is impossible to keep pace with the emerging trends. Excellence is an attitude that the whole of the human race is bornwith. It is the environment that makes sure that whether the result of this attitude is visible or otherwise. A well planned, properly executed and evaluated industrial training helps a lot in developing a professional attitude. It providesa linkage between a student and industry to develop an awareness of industrialapproach to problem solving, based on a broad understanding of process and modeof operation of organization. During this period, the student gets the real experience for working in the industry environment. Most of the theoretical knowledge that has been gained during the course of their studies is put to test here. Apart from this the student gets an opportunity to learn the latest technology, which immensely helps in them in building their career. I had the opportunity tohave a real experience on many ventures, which increased my sphere of knowledgeto great extent. I got a chance to learn many new technologies and also interfaced to many instruments. All this credit goes to the organization Prasar Bharti Doordarshan.


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CERTIFICATEThis is to certify that Rajul Kumar Pandey, a student of Bachelor of Technology(3rd year, ECE) of North Eastern Regional Institute of Science and Technology ,Nirjuli (A.P) has successfully completed his Industrial Training under the

guidance of Mr. N. A. Khan (Director) and Mr. Rajesh Chandra (Assistant Director) in Prasar Bharti Doordarshan (Broadcasting Corporation of India) Staff Training Institute (Technical) Kingsway Camp, Delhi 110009 for a period starting from 31st May , 2010 to 9th July, 2010. A project titled A STUDY on HDTV was assigned to him during this period. He worked hard and diligently completed his presentation in time. He took a lot of initiative in learning about HDTV and various applications. His overall performance during the project was excellent. We wish his all success in his career.

Mr. Rajesh Chandra Assistant Director STI (T) Kingsway Camp, Delhi

Mr. N.A. Khan Director STI (T) Kingsway Camp, Delhi


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CERTIFICATEThis is to certify that Biraj Chitrokar, a student of Bachelor of Technology (3rd year, ECE) of North Eastern Regional Institute of Science and Technology , Nirjuli (A.P) has successfully completed his Industrial Training under the guidanceof Mr. N. A. Khan (Director) and Mr. Rajesh Chandra (Assistant Director) in Prasar Bharti Doordarshan (Broadcasting Corporation of India) Staff Training Institute (Technical) Kingsway Camp, Delhi 110009 for a period starting from 31st May, 2010 to 9th July, 2010. A project titled A STUDY on HDTV was assigned to him during this period. He worked hard and diligently completed his presentation in time. He took a lot of initiative in learning about HDTV and various applications.His overall performance during the project was excellent. We wish his all success in his career.

Mr. Rajesh Chandra Assistant Director STI (T) Kingsway Camp, Delhi

Mr. N.A. Khan Director STI (T) Kingsway Camp, Delhi


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Table of ContentsAIR AND DOORDARSHAN .................................................................................................................. 1 History ............................................................................................................................................... 2 Birth ................................................................................................................................................... 3 Important events .............................................................................................................................. 3 Purposes and Objectives ................................................................................................................... 3 INTRODUCTION TO AIR AND DOORDARSHAN ..................................................................................... 4 Introduction to AIR ........................................................................................................................... 5 Studios and lab intro.......................................................................................................................... 6 Services .............................................................................................................................................. 6

AIR AND DOORDARSHAN STUDIO SET UP .......................................................................................... 1 History ............................................................................................................................................... 2 Birth .................................................................................................................

.................................. 3 Important events ..........................................................................................................

.................... 3 Purposes and Objectives .................................

................................................................................

.. 3 STUDIO ACOUSTICS ..........................................................

.................................................................. 4 Introduction to AIR ........................................................................................................................... 5 Studios and lab intro.......................................................................................................................... 6 Services .............................................................................................................................................. 6 OPTICAL FIBRE COMMUNICATIONS ................................................................................................

... 1 History ............................................................................................................................................... 2Birth ................................................................................................................................................... 3 Important events .............................................................................................................................. 3 Purposes and Objectives ................................................................................................................... 3 SATELLITE BROADCASTING ................................................................................................................. 4


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Introduction to AIR ........................................................................................................................... 5 Studios and lab intro.......................................................................................................................... 6 Services .............................................................................................................................................. 6

EARTHING ARRANGEMENT FOR BROADCAST STATIONS ...................................................................... 1 History ............................................................................................................................................... 2 Birth ................................................................................................................................................... 3 Important events .............................................................................................................................. 3 Purposes and Objectives ................................................................................................................... 3 AM TRANSMITTERS............................................................................................................................ 4 Introduction to AIR ........................................................................................................................... 5 Studios and lab intro.......................................................................................................................... 6 Services .............................................................................................................................................. 6 FM TRANSMITTERS .........................................

................................................................................... 4 Introduction to AIR ......................................................

..................................................................... 5 Studiosand lab intro.......................................................................................................................... 6 Services .............................................................................................................................................. 6 ACTIVITIES IN TV STUDIO ................................................................................................................... 1 History ............................................................................................................................................... 2 Birth ................................................................................................................................................... 3 Important events .......................................

....................................................................................... 3 Purposes and Objectives ..............................................

..................................................................... 3 MICROPHONES .................................................................................................................................. 4 Introduction to AIR ........................................................................................................................... 5

MICROPHONES .................................................................................................................................. 4 Introduction toAIR ........................................................................................................................... 5


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ALL INDIA RADIO & DOORDARSHANHISTORY: BIRTH OF ALL INDIA RADIO:The idea of regular broadcasting in India took shape for the first time in 1926,in the form of agreement enlarged between the gov.of India & private company called the Indian broadcasting Ltd. under that agreement ,a license for the const.of 2 station one at BOMBAY and other at CALCUTTA. Unexpectedly after about 3 rdyear ,the company went into liquidation on 1st march,1930 . It locked as throughintroduction of broadcasting has failed in India. While the other countries were making good programs. In march,1935 a separate dept.under a controller of broadcasting was constituted to work under the department of India & labour. The name of dept. was again changed to the dept. of information & broadcasting from 10sept,1946.

Important event of broadcasting:June, 1923 Nov , 1923 March, 1935 8June, 1936 Nov, 1937 broadcast of programmersby radio club of Bombay Calcutta radio club puts out programme. A new dep.controlle of broadcasting constitude India state broadcasting service become All India Radio AIR comes under the dept. of comm..


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23Feb, 1946 1947

AIR comes under info & arts. six radio station in India Delhi Bombay Calcutta Madras Tiruchirapalli Lucknow

After Independence:20 july, 1952 first national programmers of music broadcast from AIR. national programmers of talks commence from AIR Vividh Bharti service started. first TV station in Delhi

29 april, 1953 3 oct, 1957 1959

Purpose of the constitution of All India Radio: For the efficient supervision of programmer and for maintains of high standardsin several type of broadcasting. Programmer professionals with a background andtaste 4 music culture, current affairs, literature, agriculture , family welfare, public rel. etc. Broadcasting in India is a national service developed &operate of Gov. of India. ALL INDIA RADIO or AKASHVANI is the biggest of the 14 media unit of the ministry of information & broadcasting.

Objective of All India Radio : Broadcasting in India being a nation service constitute the most powerful mediumof mass comm..it play a significant role as a medium of info. & education. In the developing country of India Through its broadcasting AIR seek to promte educa

tion, national integration &also develop Various aspect of India culture .it also give timely assistance to public & Gov. department by quick dissemination of info. during natural damities


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INTRODUCTIONPrasar Bharati Doordarshan (broadcasting corporation of India) Delhi.Introduction to A I R.A national service planned, developed and operated by the Prasar Bharati Broadcasting Corporation of India Sound broadcasting started in India in 1927 with theproliferation of private radio clubs. The operations of All India Radio began formally in 1936, as a government organisation, with clear objectives to inform, educate and entertain the masses. When India attained Independence in 1947, AIR had a network of six stations and a complement of 18 transmitters. The coverage was 2.5% of the area and just 11% of the population. Rapid expansion of the network took place post Independence. AIR today has a network of 232 broadcasting centres with 149 medium frequency(MW), 54 high frequency (SW) and 171 FM transmitters. The coverage is 91.79% of the area , serving 99.14% of the people in the largest democracy of the world. AIR covers 24 Languages and 146 dialects in home services. In Externel services, it covers 27 languages; 17 national and 10 foreignlanguages. All India Radio (abbreviated as AIR), officially known as Akashvaniis the radio broadcaster of India and a division of Prasar Bharati Act providesfor establishment of April 1930 Broadcasting was placed under the direct controlof Government under the title 'Indian State Broadcasting Service' (ISBS) to beknown (Broadcasting Corporation of India), an autonomous corporation of the Ministry of Information and Broadcasting, Government of India. Established in 1936,[1], today, it is the sister service of Prasar Bharati's Doordarshan, the national television broadcaster. The word Akashavani was coined by Professor Dr. M.V. Gopalaswamy for his radio station in Mysore during 1936. All India Radio is one o

f the largest radio networks in the world. The headquarters is at the AkashwaniBhavan, New Delhi. Akashwani Bhavan houses the drama section, the FM section andthe National service. The Doordarshan Kendra (Delhi) is also located on the 6thfloor of Akashvani Bhavan.


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STUDIO & LABS INTRO: A TV studio is an acoustically treated compact anechoic room. It is suitably furnished and equipped with flood light for proper light effected. The use of dimmer states with flood lights enables suitable illumination level of any particular area of the studio depending on the scene to be televisedSeveral cameras are used to telecast the scene from different angles. Similarlya large number of microphones are provided at different locations to pick up sound associated with programme. The camera and microphone outputs are fed into thecontrol room by coaxial cables. The control room has several monitors to view picture picked up by different cameras. A monitor is a TV receiver that containsno provisions for receiving broadcast signals but operates on a direct input ofunpopulated signal. A large number of such monitors are used to keep a check onht contest and quality of pictures being telecast.

In addition to live studio. Video tape recording and telecoms machine rooms arelocated close to the control room. In most cases, programmes as enacted in the studio are recorded on video tape recorder (VTR) through the control. These are later broadcast with VTR output passing through the same control room. All theserooms are interconnected by co-axial cables and shielding wires.

SERVICES:AIR has many different services each catering to different regions/languages across India. One of the most famous services of the AIR is the Vividh Bharati Seva

(roughly translating to "MultiIndian service"). Vividh Bharati celebrated its Golden Jubilee on 3 October 2007. Vividh Bharati has the only comprehensive database of songs from the so termed "Golden Era" of Hindi film music (roughly from 1940s to 1980s). This service is the most commercial of all and is popular in Mumbai and other cities of India. This service offers a wide range of programmes including news, film music, comedy shows, etc. The Vividh Bharti service operateson different MW band frequencies for each city as shown below. Some programs broadcast on the Vividh Bharti:

Hawa-mahal - Skit (Radio Play) based on some novels/plays.

Santogen ki mehfil - Jokes & humour.


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AIR studio set up & Doordarshan studio setupObjectives: To originate program from studios either for live telecast or for recording on avideo tape. To knit various other sources of programs available at the production desk - camera output from studios, feed from other Kendra, outdoor, playbackfrom pre recorded tape, video graphics and characters generator etc. Processing/distribution of different sources to various destinations in technical areas. Routing of mixed program for recording/transmission via master switching room andMicrowave to the transmitter or any other desired destinations.

STUDIO CENTER:Activities in a television studio can be divided into three major areas such as:1.Studio floor/ Action area, 2.Production control room, and 3.Master control room/Central apparatus room, 4.Other facilities

Studio floor/ Action area:The studio floor is the actual stage on which the actions that will be recordedtake place. A studio floor has the following characteristics and installations decoration: sets cameras on pedestals (pod) microphones lighting rigs and the asociated controlling equipment video monitors for visual feedback from the production control room talkback system for communication

Production control room:


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Video monitor : monitors for program, preview, videotape machines, cameras, graphics and other video sources Video Switcher : a device where all video sources are controlled and taken to air. Also known as a special effects generator Audiomixing console and other audio equipment such as effects devices Character generator : creates the majority of the names and full screen graphics that are inserted into the program

Master control room:The master control room houses equipment that is too noisy. It also makes sure that wire lengths and installation requirements are within manageable lengths. This can include: Network Operations Center Transmission Control Room the actual circuitry and connection boxes of the vision mixer and character generator Central Apparatus Room Camera control units

Audio switcher


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Studio AcousticIntroduction

A broadcasting studio is a room in studio complex which has been specially designed and constructed to serve the purpose of originating broadcasting programs. Whenever any musician sings and we sit in front of a performing musician to listen to him, we enjoy the program by virtue of the superb qualities of our sensoryorgans namely ears. However, when we listen to the same program over the broadcast chain at our home though domestic receivers, the conditions are entirely different. We as broadcasters, are continuously engaged in the task of ensuring themaximum pleasure for the listener at home when the artists are performing insidethe studios. In order to achieve our goal we must thoroughly understand the characteristic of the different components involved in the broadcast chain, and inthis process we must preserve the original quality of sound produced by the artists inside the studio. The science of sound is often called Acoustics. It would bethus prudent to understand the field of acoustics as applied to broadcasting.

Acoustic TreatmentGood acoustics is a pre-requisite of high quality broadcasting or recording. Acoustic treatment is provided in studios, control rooms, and other technical areasin order to achieve the acoustic conditions which have been found from experience to be suitable for the various types of programmes. In this section problemsand design aspects of internal acoustics of a broadcast studio are explained. a)Propagation of Sound Waves

Sound waves emanating from a sound source are propagated in all directions. These sound waves are subject to reflection, absorption and refraction on encountering an obstacle. Extent to which each of these phenomenon takes place depends upon the structure and shape of the obstacle, and also on the frequency of sound waves. In close rooms, the sound would be reflected and re-reflected till the intensity weakens and it dies down. Physical characteristics of sound waves are thusmodified in various ways before they reach the human ear. These reflected wavescan create echo effect in the room. To achieve the desirable effects of the reflected sound, the dimensions and shape of the room are decided with due care andacoustic treatments are also provided on the various surfaces.


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b)

Reverberation Time(R/T)

In any enclosed room when a sound is switched off, it takes a finite length of time to decay to inaudibility. The hanging-on of the sound in a room after the exciting signal has been removed, is called reverberation and the time taken for the sound to decay to one millionth of its initial value, i.e. 60 dB, after the source has stopped, is termed Reverberation Time(R/T).c)

Factor Covering Reverberation Time

R/T of a room depends upon shape and size of room and on the total absorption offered on boundary surfaces. For a room of given volume and surface area, the R/Tcan be derived by Eyrings formulaR/Twhere R/T V S

= = = =

0.049 V S ln (1 ) Reverberation time in seconds Volume in cubic ft. Total surfa

e area of room in Sq.ft. Average absorption coefficient

Average absorption coefficient ( ) is given by S11 S 2 2 ......... S n n S1 S 2 ....... Sn

Where S1, S2.Sn are the areas (in sq. ft.) of different materials provided, and 1 ,2 n are the absorption coefficients of these materials. of acoustic material is ined as the ratio of absorbed sound to the total incident energy of sound. An open window absorbs/allows to pass all of the sound energy striking it and reflects none. Thus it has of unity. of practically all acoustic materials vary with frequency.d)

Effects of Reverberation on Programme It influences the audio

Reverberation is the most important single parameter of a room. programs in following ways:

Volume of program increases due to reverberation of sound. This is a desirable feature, however, too much of reverberation may impair the quality of proram and,therefore, should be controlled.


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Reverberation results in prolongation of sound inside the room. This leads to blending of one sound with the next and produces a very pleasant continuity in theflow of music. Too much of prolongation, however, may create loss in intelligibility of program due to decrease in clarity. Reverberation time of a room is dependent on frequency. Therefore, it modifies the frequency characteristics of thetotal sound field inside the room. High R/T at mid and high frequencies lead toincreased liveness and that at low frequencies increases warmth. This effect can beused judiciously for desirable qualities. Acoustic absorbers

e)

Acoustic absorbers are provided on the inner surfaces of the room to achieve optimum R/T characteristics. Different absorbers have different absorption characteristics. No single absorber generally provides uniform absorption over the complete frequency spectrum. Some of the commonly used absorbers are: i) Porous Materials: Mineral wool, glass wool, etc. are members of this class. These materialsare very good absorber and are most effective in mid and high frequencies, however, these cannot be used without some facing material. Carpets and curtains alsofall in this category. ii) Fibrous Materials: Celotak, insulation boards, perfotiles, jolly-lowtone tiles etc. fall in this category. Absorption of these mater

ials depends upon their softness. Absorption efficiency of these materials depends upon the trapping and dissipation of sound energy in tiny pores. Absorption gets reduced if the surface pores are filled with paints etc. These materials have very poor absorption on low frequencies. However appreciable improvement at these frequencies is possible by providing air-gap behind. iii) Panel Absorbers: Panel absorbers are thin sheets/membranes with an air cavity behind. The mass ofthe panel and the springiness of the air in the cavity resonant at some particular frequency. Panel absorbers with 3mm teak ply-facing + 50mm air gap + 25mm mineral wool resonates at about 125Hz. This is generally used as low frequency absorber(LFA). iv) Perforated Panel Absorbers: Perforated hardboard (PHB) spaced from the wall constitute a resonant type of sound absorber. The absorption can be considerably enhanced by inserting a suitable porous/fibrous damping materials inthe air cavity. The absorption pattern can be varied by adjusting the front and

rear air gap from the damping material. Absorption coefficient of these absorber depends on the percentage open area of PHBs also.


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g)

Design of Room Acoustic

Design for correct reverberation time consists of estimating the total absorption which must be present in the studio. This is calculated by Eyrings Formula, some of the absorption is offered by windows, doors, flooring and artists inside the studio. For the balance requirement sound absorbing materials are provided onwalls and ceiling surfaces. Calculations are generally made at six spot frequencies of 125, 250, 500, 1000, 2000 and 4000 Hz. Quantities of materials of known absorption coefficients are selected by trial and error method so that R/T requirements are met within +5% of the optimum R/T at all these frequencies. Computeraided design for the same has also been evolved. Thereafter these acoustic materials are distributed on various surfaces for proper diffusion of sound in the studio.


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Optical Fiber CommunicationIntroduction: Fiber optics is being used to transmit television, voice, and digital data signals by light waves over flexible hair like threads of glass and plastic. It has evolved into a system of great importance and use since the 1980s. The advantages of fiber optics compared to coaxial cable or twisted pair cable, are endless. Millions of dollars are being spent to put light wave communicationsystems into operation, as a result of its performance. Definition: Optical Fiber Communication System converts electrical signal into light signal witch afterpassing through optical fiber cable is reconverted into electrical signal by using optical Receiver Composition of optical fiber: Silica based glass or plasticfilaments are spun and packed into bundles of several hundreds or thousands. Bundles may be put together as rods or ribbons and sheets. These bundles are flexible and can be twisted and contorted to conduct light and images around corners The thin glass center of the fiber where the light travels is called the core. Theouter optical material surrounding the core that reflects the light back into the core is called the cladding. In order to protect the optical surface from moisture and damage, it is coated with a layer of buffer coating.


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Operation in optical fiber system: In a fiber optic system, there are a few major components to perform the task of communication. The Input Modulator is needed; this modulates the incoming signal with a light beam. A light emitting deviceis used; it can be either a light emitting diode (LED) or a semiconductor laserdiode. A fiber optic cable is used as a transportation medium. A fiber optic system converts an electrical signal to an infrared light signal, and then transmits the signal onto an optical fiber. An Output Modulator is used to separate thesignal from the light beam.

Types of optical fiber: 1.Step index: This cable index of refraction for the core and the cladding. It causes deformations due to the various paths lengths of the light ray. This is called modal distortion. It is the cheapest type of cabling. Within the cladding and the core, the refractive has a specific index is constant. Graded index : In graded index fiber, rays of light follow sinusoidal paths. Although the paths are different lengths, they all reach the end of the fiberat the same time. Multimode dispersion is eliminated and pulse spreading is reduced. Graded Index fiber can hold the same amount of energy as multimode fiber.The disadvantage is that this takes place at on one wavelength


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Satellite communication

Satellite transmission What is satellite: A satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.

Purpose of satellite communication: To cover Wide Area in one go. To provide signal for distribution over AIR, Doordarshan Networks & cable. To have interlink between different AIR&TV centres for contribution of programmes like News & Current Affairs.

Basics of satellite communication: Satellite basically a spacecraft placed in orbit around earth carrying microwave receive & transmit equipment on Board


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Essentially a Microwave Link Repeater Frequencies capable of passing through Ionosphere (Microwave frequencies) use Microwave frequencies permit transmission ofdata at high rate. Reason of satellite revolution: A single satellite can provide coverage to over 30% of Earths surface. It is often the only solution for developing areas It is ideal for broadcast applications It can be rapidly deployed. It is scalable. Depending on application, there is no need for the local loop Receving and transmitting device: LNA (Low Noise Amplifier) or LNB (Low Noise Block) LNA - amplifies RF signal from the antenna and feeds it into frequency converter (typically IF of 70/140 MHz) LNB - amplifies RF signal from the antenna andconverts it to an L-band signal (9502100 MHz)

LNA is more precise and stable but more expensive than LNB (LO stability). Transmit power amplifiers provide amplification of signals to be transmitted to the satellite Transceiver takes 70/140 MHz signal and amplifies it to either C or Ku-band final frequency. Block Up-Converter takes L-band signal and amplifies it toeither C or Ku-band final frequency.


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Earthing Arrangement for a Broadcasting StationDefinition: An Electrical connection to the general mass of earth to provide safe passage to fault current to enable to operate protective devices and provide safety to personnel. Or The term Earthing means connecting the neutral point of asupply system or Non-current carrying parts of electrical apparatus to the general mass of earth in such a manner that at all times an immediate discharge of electrical energy takes place without danger. Objective of earthing: To ensure that no part of equipments, other than live parts, assume dangerous potential. Toallow sufficient current to flow safely for proper operation of protective devices. To suppress dangerous potential gradients on the earth surface which may cause incorrect operation of control & protective devices and also may cause shockor injury to personnel. Provide stability of voltage, prevent excessive voltagepeaks during disturbances and protect against lightning surges.

Types of Earthing:Neutral Earthing : deals with the earthing of system neutral to ensure system security and protection.

Equipment Earthing : deals with earthing of non-current carrying parts of equipment to ensure safety to personnel and protection against lightning. Danger posedto human being by electric current: The currents, and the dangers posed to thehuman being, are dependent on the voltage as well as on the electrical resistance of the human body (the inner body resistance plus the skin resistances). The c

ritical electrical voltages with which we are involved in our professional and private lives are normally 220 volts, and up to 440 volts in the case of three-phase current. The intensity of the inner body resistance is critically dependenton the path of the current in the body. Average values for the inner body resistance along various paths taken by the current are as follows: Hand hand 1200 ohms Hand feet 900 ohms Hands feet 600 ohms


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Thus, if the voltage with which a human being comes into contact and the resistance of the human body are known, the intensity of the current canbe easily calculated. Further, if the current intensity can be calculated, then the degree of danger posed to the human being can be assessed too. The electrical resistivity of the earth i.e resistance of the earth to the flow of current is defined as soil resistivity Earth resistivity varies from a few ohm meters along some sea coaststo many thousands of ohm meters in rocky, mountainous country . Theoretically, the resistance to remote earth of an earth electrode can be calculated. This calculation is based on the general resistance formula: R = (r x L) / A where: R = resistance to remote earth (Ohms) r = soil resistivity (Ohms-cm) L = length of conducting path (cm) A = cross-sectional area of path (cm) The assumption in the general formula is that the resistivity of the soil is constant throughout the considered area, or averaged for the local soil. So the target of providing good earthing system is to provide least resistance path by earth electrode of least earth resistance in a least resistivity soil.


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AM TransmittersThere are various MW AM transmitters all over the India. The SW transmitters arevery few and used for mostly international broadcasting purpose but soon will vanish. The transmission bands used for are as follows

AM transmission bands:Long wave 200-400 kHz Medium wave 531-1602 kHz Short-wave 3.2-26.1 MHZ

Sub systems of a transmitter:1.Radio frequency slection 2.Audio frequency section 3.Control and instrumentation 4.Cooling and ventilation 5.Power supply system 6.HT supply

Power amplifiers: Normally Class C or Class D high efficient amplifiers in both MW/SW Employs Highlevel plate modulation Water or air cooled Beam power tetrodes of Ceramic/Glasstube Directly heated cathode


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Screen is also modulated

Audio circuits in tube TXs:Consists of High Pass Filters Pre amplifiers Pre- correctors for non linearity compensation AF Drivers Modulators - Normally push pull Class B Feed back and compensation circuits

SW transmitters:Major differences are Output is balanced hence balun is used Rf amplifiers are wide band (3 to 26 MHz) Final stages are tunable in short time Uses motor controlled variable capacitors and inductors VVC replaces conventional disc capacitors Variable oscillator frequency

Cooling and ventilation: High power transmitters are cooled by air/water Distilled water of low conductivity is used for HT stages


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Hyper vapour-tron and condensed vapour cooling technique

Low pressure and High pressure fans Heat exchangers for cooling hot water

Output impedance: MW Transmitters 50 ohm (RF cable) 60 ohm (Quasi co-axial) 120 ohm Balanced 30hm

BLOCK DIAGRAMVOF AM TRANSMITTER:


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FM TransmittersThe FM transmission has been developing day by day with the evolution of value added services and digital radio broadcasting. RDS and SCA systems are examples of it. AIR New Delhi uses a solid state 10 kW VHF FM transmitter manufactured byBEL (Bharat Electronics Ltd.) for mono and stereo. The value added services likeradio traffic (RDS) and Subsidiary communications authority (SCA) are now a option with the FM transmission to meet the needs of a broad spectrum of audiencesand the emergence of new multimedia forms. Following is the list of BELs FM transmitters installation in India.


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BLOCK DIAGRAM OF 2*3kW FM TRANSMITTER:


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The FM antenna has been shown below:

A typical FM Mast:


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Activities in TV Studio


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DIVIDED INTO TWO MAJOR AREAS SUCH AS : Action Area Production Control Room

ACTION AREA:This place requires large space and ceiling as compared to any other technical area. Action in this area includes staging, lighting performance by artists and arrangement to pick up picture and sound. This place requires large space and coiling as compared to any other technical data. Very efficient air conditioning because of lot of heat dissipation bay studio light and presence of large number of persons including invited audience performing artists and operational crew. Uniform and even flooring for smooth operation of camera trollies and microphone etc. Acoustic treatment keeping in mind that a TV studio is a multipurpose studiowith lot of moving person and equipment during production. Supporting facilities like properties, makeup and wardrobe etc. Digital clock display. Audio and video monitoring facilities. Pick up wall sockets for audio operations. Luminariesand suspension system having grids or battens. Tie lines box for video and audiofrom control room. Cyclorama and curtain tracks for blue and black curtain forchrome keying and limbo lighting respectively.

Camera Chain:A typical three tube camera chain is described in the block diagram. Tube powersupply section provides all the voltages required grids of electron gun. Horizontal and vertical deflection section supplies the saw tooth current to the deflection coils of scanning the positive image formed on the target. The built in syn

chronous pulse generator provides all the pulses required for the encoder and colours bar generator of the camera. The signal system in most of the camera consists of processing of the signal form red, blue and green tube. Some of the camera us-e white, blue and red tubes instead of R,G, B system. the processing of redand blue channel is exactly similar. Green Channel, which also called a reference channel, has slightly different electronics concerning aperture correction. So if we understand a particular channel, the other channels can be followed easily. In each camera signal are given to generate synchronous pulse and black burst pulse for a good picture in television.

Camera control unit:


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The TV camera which includes camera head with its optical focusing lens. pan andtilt head, video. Single preamplifier view finder and other associated electronic circuiting and mounted on cameras trolley and operate inside the studio. heoutput of camera of cameras in preamplifier in the head and then connected to the camera control unit through long multicore cable. In this room shot can be decided to which camera can be taken. Camera position can also be control in thisroom. CCU can control three colour RGR= .10+.59+.11=100% In CCU monitoring sources, monitoring facilities and pulse disribution amplifies are available. Vectroscope provides on overview of control and connection function. Monitor can detectany fault in the camera. The color camera chain comprises the following basic assembly: color camera Camera control unit Connection unit Multiwire cable Camview finder The color camera chain meets the ultimate requirement in the fieldof studio. It features easy handling, operational safety and good serviceability. It can be operated either with multiwire or with coax/triax camera cable. Thecolor camera head, the camera control unit and remote control unit associated with the setup control console or remote control console are each equipped with amicrocomputer. The color camera uses a 3-tube RGB system with high grade beam splitter. It is equipped with 1-inch plumbicon pickup tubes with dioxide gun system, bias light and ABC facilities. Various high grade lenses of different brandsare available for camera. The camera control unit is of compact design. The connection between camera head and camera control unit can be established either viaa multiwire camera cable or via a coax/triax camera cable. DIMMER ROOM Dimmer Room consists of light control system which give the various lightening effects in the studio. General Description Of Light Control System : The light control sy

stem designed for television studio comprises of i. A light control desk. ii. Electronic dimmer rack. iii. Power distribution and control panel. iv. Studio lights. v. Talk back system. * The function of Light Control Desk is to enable the operator to remotely select the studio lamps, that need to be turned on for a particular scene & also enable control of intensity of some of the lamp, required for color matching.


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* Using Electronic Dimmer, the operator is able to control the intensity of lampremotely. The intensity of a group of the lamps can be adjusted individually orin one of the two scenes. *The system has been designed for large number of theloads, distributed on 415V,3 phase, 50Hz, 4 wire mains. The phase distributionboth on the rack as well as on the light control desk are marked with dots. Thishelps to distribute high loads on the three phase more or less equally. *Any individual intensity control fader can be connected by the means of 3 position lever switch to any one of the three control in each present. Scene A OFF Scene B *Two electronic dimmer are wired as one plug in module, each rated at 2.5 KW where as one dimmer is wired in one plug in module of 5.0 KW. * The dimmer rack isinterconnected with light control desk by means of multi core 0.2 qmrs. Flexiblecopper PVC unarmored control cable. Talk Back System: It is a in house communication system. This type of system is very useful for TV Studios, Theaters etc. this system is based on duplex communication system & has 4 stations one master and three slaves. Special advantages og this :(1) Any one can talk to any one. (2) Master can talk to all stations at a time. (3) It can hand off loud speaking type. Power Distribution and Control System (panel is helpful in distribution ofpower to different racks). Light Control: The scene to be television must be well illuminated to produce a clear and noise free picture. The lighting should also give the depth, the correct contrast and artistic display of various shades without multiple shadows. The lighting arrangements in a TV studio have to be veryelaborate. A large number of lights are used to meet the need of "key" "fell" and "back" lights etc. Lights are classified as spot and soft lights. These are suspended from motorized hoists and telescopes. The up and down movement is remot

e controlled. The switching ON and OFF is lights at the required time and theirdimming is controlled from the light control room using SCR dimmer controls. These remotely control various lights inside the studios. V. T .R. (Video tape recording): It is the most complex piece of studio equipment with analog and digitalprocessor servo system, micro-processor, memory, logic circuits and mechanicaldevices etc.V.T.R


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room is provided at each studio center. It houses at least two console type 'A video tape recorders' (V.T.R.) and a few broadcast standard video cassette recorder (V.C.R.).Here recording is done on playback format CAM. Quality of recorded programme is tested immediately after recording is completed so that if there isany technical or any other problem the same could be rectified and the final recording is of good quality. During the original transmission the programme tapesare played back from the V.T.R The audio and video labels can also be adjusted from here. The format of programme from mini D.V.C to J3 is transferred in the V.T.R room, DD news, OTR(off telecast recording) is also recorded for the use in original news programme. Specifications: Video Cassette Recorders Operational Environment 1. Operating temperature 5deg C to 40deg C. 2. Storage temperature -20deg C to 60 deg C. 3. Location to avoid : *areas whose BVW-70P will be exposed todirect sunlight or any other strong light. * industry areas or areas where it is subject to vibration. *areas with strong electric or magnetic fields *areas near heat sources Technical Information: General Specifications Power requirementsPower consumption Operating temperature Storage temperature Humidity Weight Dimensions Tape speed Record & playback time Fast forward/rewind time

AC 90 to 265V, 48 to 68 Hz 240W 5deg C to 40deg C -20deg C to 60deg C Less than80% 30 Kg. 427*237*520 mm/w/h/o 101.51 mm/s 100 minutes max. less than 180 seconds

PCR (PRODUCTION CONTROL ROOM):The video and audio outputs are routed through a production control room. This i

s necessary for a smooth flow and effective control. of the programme material.This room is


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called the production Control Room' (PCR) It is manned by the programme director, his assistant a camera control unit engineer a video mixer expert a sound engineer and a lighting engineer. The programme directors with the help of this staff effects overall control of the programme whole it is telecast live or recordedon a VTR. The video and audio outputs from different studios and other sourcesare terminated on separate panels in the control room. One panel contains the camera control unit and video mixer. In front of this panel are located a number of monitors for editing and previewing a incoming and outgoing programmes. Similarly another panel houses microphone controls. This panel is under control of thesound engineer who is consultation with the programme director selects and controls the available sound output. The producer and the programme assistant have in front of them a talk back control panel for giving instruction to the camera man, audio engineer and floor manager. The producer can also talk over the intercom system to the VTR. The lighting is controlled by switches and faders from a dimmer console which in also located in the control room.

PCR includes following two sections:

Vision Mixer Audio distribution amplifier-ADA

MIKE-1 MIKE-2 MIKE-3

TAGMATRIX

PATCH PANEL

AUDIO AMPLIFIE R

BLOCK

Audio Distribution Amplifier

Mon. O/P Studio

AUDIO CONSOLE UNIT

VTR

ENG-CAMERA:


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Eng means Electronic News Gathering. This camera is used for news coverage. It does not contain vacuum tube, rather contain charged couple device CCD. CCD is compact and small in size. This camera is portable and movable. The features of camera are as follows: The camera contain three CCD. The camera is battery operated and battery used is 12V,SA and chargeable. The camera can be operated by AC supply and for that AC adapter is used. The camera has audio monitor. The camera has video recorder which is also compact. The video tape is of 30 minutes. The camera make use of lens assembly for focusing purposes. The different types of mikes used are as follows: Gun mike Lapel mike RF mike The gun mike has high gain.The lapel mike is used by news readers.


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MicrophonesINTRODUCTIONMicrophone is a transducer. It converts sound wave (acoustical energy) into electrical energy.

Five important characteristics of microphone Operating principle Frequency rense Directionality of microphone Electrical output and Physical design of the microphone

Applications: Telephones Tape Recorders Karaoke System Hearing Aids

Microphone Classifications: Acoustical Classification Electrical Classification Polar pattern-wise Classification

Acoustical Classification: 1.Pressure-operated Microphone They are depending on the output voltage from a microphone and the sound pressure on it. Sound Pressure is applied on one side of the diaphragm. Electrical output Sound Pressure. Theoretically omnidirectional.


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Electrical Classification: 1. Electrodynamic Moving coil Microphone A magnet is moved near a coil of wire an electrical current is generated. Usingthis electromagnet principle, the dynamic microphone uses a wire coil and magnetto create the audio signal. The diaphragm is attached to the coil. Used in liveperformance where rough handling is common. Examples- AKG D-202, D-222, D-900,D-770, D-190E, SM58, SM57, SM48 etc.

AKG D-770

Electrodynamic Moving coil Microphone

2. Ribbon Microphone: It uses a thin aluminum, duraluminum or nanofilm ribbon placed between the polesof a magnet to generate voltages by electromagnetic induction. Very sensitive to shock and large sound volumes. Very delicate. Very low impedance and hence uses in-built transformer. Bidirectional.


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Ribbon Microphone

Bidirectional

3. Condenser Microphone: The diaphragm is one plate of a capacitor (condenser) containing an electrical charge. Electrical charge is applied to either or both plates. Sounds pressure changes the distance between two plates and causes variation in the capacitance. Requires pre-amplifier. Requires external supply known as phantom power (-9 to 25V). Large diaphragm gives flattering response. Resonant frequency at the upperend of audio spectrum. Examples- C2000B, C3000B, SM86, SM94, SM81 etc.

Condenser Microphone

SM 94


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4. Electret Microphone: It is a modified form of condenser microphone. It does not use external power supply. Uses a special type of capacitor which has a permanent voltage built in during manufacture. Pre-amplifier requires power supply. The principle of operation is that sound waves impinging on the diaphragm cause the capacitance between the diaphragm and the back plate to change, this in turn induces voltage varianceon the back plate. The output is independent of the diaphragm surface area. Light and small in size. Excellent quality/price ratio.

Electret Microphone


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Polar -Wise Classification: Omnidirectional Microphones: Omnidirectional microphones are sensitive to sound from all directions.

Bidirectional Microphones: Bidirectional microphones pick up from the front andrear and have null points to either side. Cardroid Microphones: Cardioid microphones are directional have a heart shaped polar pattern. This means they pick up sound mainly from the front and are least sensitive to sound from the rear.

Hypercardroid Microphones: Hyper-cardioid microphones have a similar pick up pattern to the cardioid mics but are more directional and dont pick up as much from the side.

Omnidirectional Microphones

Bidirecti onal Microphones


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Cardroid Microphones

Hypercardroid Microphones

SPECIAL MICROPHONES Lip Microphone: A close talking microphone. Designed to ensure constant spacing between the microphone body and the lips of the user. Also known as noise canceling microphone.


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*Contact

Microphone:

Size is small. Attached with the sound source itself. Pickup vibration pulsing through solid. Attach to a point so that it should not come in the view of camera. HF response is good but LF response is bad.

*Parabolic Microphone : A cardioid microphone is placed at the focal point of a parabolic reflector. Theparabolic reflector is made of sheet metal or stratified polyester or glass fibre. Low frequency pickup is proportional to the diameter of the reflector. Usedfor recording faint sounds such as birdsongs.

Parabolic Microphone

Boundary Microphone

*Boundaryreceptacle.

Microphone

:

A small capsule microphone usually an electret, is housed in a flat


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The flat receptacle works as a plane reflective surface. The directivity is hemispherical at all frequencies. More dynamic range and clarity. Omnidirectional. Also known as PZM.

*Wireless

Microphone:

These are ordinary microphones with an FM transmitter. Provides complete freedomof movement. Omnidirectional. Interference from outside source. Suitable for stage performance. Suitable for places where laying of microphone cable is not possible.

Important characteristics of microphone: Frequency ResponseFrequency response refers to the way a microphone responds to different frequencies. It is a characteristic of all microphones that some frequencies are greaterand others are attenuated (reduced). It depends upon:- Direction of arrival ofsound and distance between the source and the microphone.

DirectivityMicrophone have directional characteristcis: Omnidirectional:-Pick up equally atall angles. Bidirectional:-Pick up equally from front and rear . Unidirectional:-microphone which pick up maximum rom front .


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SensitivityThe ability to pick up weak sound and to deliver more electrical Signal determines the sensitivity.

DistortionThe inability to maintain linearity, resulting in the addition of unwanted HARMONICs,m called Harmonic Distortion .The inability to pass the complete audio spectrum equally, called Frequency Distortion .The inability to handle TRANSIENTs, called Transient Distortion .The inability to pass all signals in the same amountof time, called Phase Distortion

Placement of Microphone:a) As far as possible, microphone should be placed with its zero axis facing thesource of sound to avoid off axis colouration.

b) Phasing of microphone:-Whenever two or more microphone are used with their outputs mixed together, it should be ensured that their outputs are in phase. c) Working distance:-microphone should be placed 30-45cm from the source of sound soas to avoid proximity effect. d) Talking very close to a microphone may cause sound like P. Hence it should be avoided.


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TV TRANSMITTERSThe TV transmitters are broadly classified as:

a) High Power Transmitter(HPT):TV transmitters having output power 1kW and above (1kW, 10kW, 20kW)

b) Low Power Transmitter(LPT):All TV transmitters having output power less than 1kW and more than or equal to50W (50W, 100W,300W,500W)

c) Very Low Power Transmitter(VLPT):Output power of 10W.

Frequency spectrum of TV Transmission:LF MF HF VHF UHF SHF 30 300 03 30 300 3 300 kHz 3000 kHz 30MHZ 300MHZ 3000MHZ 30GHZ

VHF : 30 - 300 MHz: Band I (40-68 MHz) Band II (88-108 MHz) Band III (174-230 MHz) TV Channel 4 Channel Spacing - 7 MHz FM Sound Broadcasting Channel Spacing -100 KHz CH 5 CH 12 Channel Spacing 7 MHz


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UHF : 300 3000 MHz: Band IV (470 606 MHz) CH 21 CH 37 Channel Spacing - 8 MHznd V (606 798 MHz) CH 38 CH 61 Channel Spacing - 8 MHz SHF : 3 30 GHz: C Ba. C Band 3.7 5.9 4.5 6.7 - 4.2 GHz (DL) - 6.4 (UL) - 4.85 GHz (DL) - 7.02 (UL)

LOW POWER TRANSMITTER CHAIN:LNBC TV ANTENNA

PDA Audio IRD RF Cable Video EXCITER PA CH.FILTER

RF CABLE DC

OR TVRO (SATELLITE RECEIVER)

WORKING PRINCIPLES OF LPTs: The Transmitter design is based on solid state techniques employs modular construction. The video and audio signals are processed in the exciter electronics andmodulated at low level,at IF frequency of 38.9 MHz & 33.4 MHz,respectively. Picture IF = 38.9 MHz Sound IF = 33.4 MHz


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Equipments required for LPT TV transmitter: Two 500W VHF/UHF Solid state TV Transmitter Working in passive Standby TVRO / IRD System Input Monitoring Rack (common to Both Transmitters Micro controller based SCU (station control unit) housedin Input Rack 15 KVA/25 KVA Diesel Generator with AMF Panel 1 kVA UPS 6 kVA UPS 10 kVA Automatic Voltage Regulator (AVR) Room Temperature Sensor Smoke Detector 14 inch Colour TV set Modem Connected to SCU Computer at DMC Telephone line beween DMC & LPT.

Transmitter (VHF or UHF): Only one Exciter for two 500 W transmitters Protection circuits in RF stages forSafety Against 1. VSWR 2. Thermal & Excess power faults to prevent failure of RF devices Both Transmitters are Micro controller Based Remotely Controllable


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500W VHF employs two 400W PAs(BEL) 500W UHF employs four 150W PAs(BEL) 500W UHFemploys two 300W PAs(WEBEL) Video/Audio 1 is Master & Video/Audio 2 is Slave Video/Audio Selectable from SCU


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CONCLUSIONThe technology currently in use at Prasar Bharati has improved significantly. Atthis stage there has been advancement in signal reception quality as systems have changed from analog to digital with the advancement in different audio and video compression techniques. For Doordarshan, DTH (Direct To Home Service) satellite services have become more user friendly and also evolution of SDTV into HDTVhave made it a popular product among the people of India. It is also accessiblefrom remote areas with more channel and better reception. In AIR also, there have been a lot of advancements being made such as transmission of more value added services such as RDS, SCA, etc. These value added services have added a different taste in listening radio. Also, presently the Prasar Bharati, i.e. Doordarshan is all going to broadcast the commonwealth games to be held in New Delhi in HDTV. Slowly but steadily, the AIR and Doordarshan family of Prasar Bharati is growing day by day and working for the next generation broadcasting technique in India.


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36132194 pdf training report prasar bharati new delhi

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