industrial training report - butola

8/22/2019 Industrial Training Report - Butola

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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.

DRONACHARYA COLLEGE OF ENGINEERING, GURGAON

SUBM ITTED To:- SUBM ITTED By:-

H . O. D. ARJUN BUTOLA

Electronics and Communication 14150, ECE-I

DCE, GGN

24th

JUNE3rd

AUGUST, 2013


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ACKNOWLEDGEMENT

This report is an outcome of the practical training which I have gone through atDoordarshan Kendra, Mandi House, New Delhi.

I would like to express deep sense of gratitude towards Mr. Gurjeet Singh(ADE,Doordarshan) who permitted us to undergo this training. I would like to expressmy special thanks to Mr. R N Rai(AE, Doordarshan) for helping me inunderstanding the technical aspects of Broadcasting.

It is a great pleasure to express my heart full thanks to the staff ofDoordarshanKendra who helped me directly or indirectly throughout the successfulcompletion of my training.

(ARJUN BUTOLA)

(7A30)


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PREFACE

With 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 born with. 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 provides a linkage between a

student and industry to develop an awareness of industrial approach to problem

solving, based on a broad understanding of process and mode of 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 anopportunity to learn the latest technology, which immensely helps in them in

building their career.

I had the opportunity to have a real experience on many ventures, which increased

my sphere of knowledge to great extent. I got a chance to learn many new

technologies and also interfaced to many instruments. All this credit goes to the

organization Doordarshan Kendra, Mandi House, New Delhi.


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CERTIFICATE

This is to certify that Arjun Butola, a student of Bachelor of Technology (2nd

year,

ECE) of Dronacharya College of Engineering, Gurgaon has successfully completed

his training under the guidance of in Doordarshan Kendra, Mandi House, New

Delhi for a period starting from 24th

June to 3rd

August, 2013.

A project titledA STUDY on HDTV was assigned to him during this period. He

worked hard and diligently completed his presentation in time. He took a lot ofinitiative in learning about HDTV and various applications. His overall

performance during the project was excellent. We wish his all success in his

career.

Mr. Gurjeet Singh Mr. R. N. Rai

Assistant Director(Engg.) Assistant Engineer

Doordarshan Kendra Doordarshan Kendra

Mandi House, Delhi Mandi House, Delhi


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Table of Contents

AIR 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



STUDIO ACOUSTICS............................................................................................................................ 4

Introduction to AIR .................................................................................................................. 5


Services................................................................................................................................... 6

OPTICAL FIBRE COMMUNICATIONS .................................................................................................... 1

History .................................................................................................................................... 2

Birth........................................................................................................................................ 3



SATELLITE BROADCASTING ................................................................................................................. 4


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Services................................................................................................................................... 6

EARTHING ARRANGEMENT FOR BROADCAST STATIONS......................................................................1

History .................................................................................................................................... 2

Birth........................................................................................................................................ 3



AM TRANSMITTERS............................................................................................................................ 4



Services................................................................................................................................... 6

FM TRANSMITTERS ............................................................................................................................ 4



Services................................................................................................................................... 6

ACTIVITIES IN TV STUDIO.................................................................................................................... 1

History .................................................................................................................................... 2

Birth........................................................................................................................................ 3



MICROPHONES .................................................................................................................................. 4


MICROPHONES .................................................................................................................................. 4



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ALL INDIA RADIO & DOORDARSHAN

HISTORY:

BIRTH OF ALL INDIA RADIO:

The idea of regular broadcasting in India took shape for the first time in 1926,in the form ofagreement enlarged between the gov.of India & private company called the Indian broadcastingLtd. under that agreement ,a license for the const. of 2 station one at BOMBAY and other atCALCUTTA.

Unexpectedly after about 3 rd year ,the company went into liquidation on 1

stmarch,1930

.

It locked as through introduction of broadcasting has failed in India. While the othercountries were making good programs.

In march,1935 a separate dept.under a controller of broadcasting was constituted to work under thedepartment of India & labour.

The name of dept. was again changed to the dept. of information & broadcasting from 10 sept,1946.

Important event of broadcasting:

June, 1923 broadcast of programmers by radio club of Bombay

Nov , 1923 Calcutta radio club puts out programme.

March, 1935 A new dep.contr oll e of broadcasting consti tude

8June, 1936 I ndia state broadcasting servi ce become Al l I ndia Radio

Nov, 1937 AI R comes under the dept. of comm..


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23Feb, 1946 AI R comes under i nfo & arts.

1947 six radio station in I ndia

Delhi

Bombay

Calcutta

Madras

Tiruchirapalli

Lucknow

Af ter I ndependence:

20 jul y, 1952 fi rst national programmers of music broadcast f rom

AIR.

29 apr il , 1953 national programmers of talks commence fr om AIR

3 oct, 1957 Vividh Bharti service started.

1959 fi rst TV station in Delh i

Purpose of the constitu tion of Al l I ndia Radio:

For the efficient supervision of programmer and for maintains of high standards in several type ofbroadcasting.

Programmer professionals with a background and taste 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. ALLINDIA RADIO or AKASHVANI is the biggest of the 14 media unit of the ministry ofinformation & broadcasting.

Objective of All I ndia Radio :

Broadcasting in India being a nation service constitute the most powerful medium ofmass comm..it play a significant role as a medium of info. & education. In thedeveloping country of India Through its broadcasting AIR seek to promteeducation, national integration &also develop

Various aspect of India culture .it also give timely assistance to public & Gov. department byquick dissemination of info. during natural damities


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INTRODUCTION

Prasar Bharati Doordarshan (broadcasting corporation of India) Delhi.

In t roduct ion to A I R.

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

Sound broadcasting started in India in 1927 with the proliferation of private radio clubs. Theoperations of All India Radio began formally in 1936, as a government organisation, with clearobjectives to inform, educate and entertain the masses.

When India attained Independence in 1947, AIR had a network of six stations and a complementof 18 transmitters. The coverage was 2.5% of the area and just 11% of the population. Rapidexpansion of the network took place post Independence.

AIR today has a network of 232 broadcasting centres with 149 medium frequency(MW), 54 highfrequency (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 dialectsin home services. In Externel services, it covers 27 languages; 17 national and 10 foreignlanguages.

All India Radio (abbreviated as AIR), officially known as Akashvani is the radiobroadcaster ofIndia anda division of Prasar Bharati Actprovides for establishment of April 1930 Broadcastingwas placed under the direct control of Government under the title 'Indian State BroadcastingService' (ISBS) to be known (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 inMysore during 1936.

All India Radio is one of the largest radio networks in the world. The headquarters is at the

Akashwani Bhavan, New Delhi. Akashwani Bhavan houses the drama section, the FM sectionand the National service. The DoordarshanKendra ( Delhi) is also located on the 6

thfloor of

Akashvani Bhavan.
http://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Prasar_Bharatihttp://en.wikipedia.org/wiki/Government_of_Indiahttp://en.wikipedia.org/wiki/Government_of_Indiahttp://en.wikipedia.org/wiki/Government_of_Indiahttp://en.wikipedia.org/wiki/All_India_Radio#cite_note-0http://en.wikipedia.org/wiki/All_India_Radio#cite_note-0http://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/New_Delhihttp://en.wikipedia.org/wiki/New_Delhihttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/Delhihttp://en.wikipedia.org/wiki/Delhihttp://en.wikipedia.org/wiki/Delhihttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/New_Delhihttp://en.wikipedia.org/wiki/Doordarshanhttp://en.wikipedia.org/wiki/All_India_Radio#cite_note-0http://en.wikipedia.org/wiki/Government_of_Indiahttp://en.wikipedia.org/wiki/Prasar_Bharatihttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Radio


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STUDIO & LABS INTRO:

A TV studio is an acoustically treated compact anechoic room. It is suitably furnishedand equipped with flood light for proper light effected.

The use of dimmer states with flood lights enables suitable illumination level of anyparticular area of the studio depending on the scene to be televised Several camerasare used to telecast the scene from different angles. Similarly a large number ofmicrophones are provided at different locations to pick up sound associated withprogramme.

The camera and microphone outputs are fed into the control 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 contains no provisions for receiving broadcast signalsbut operates on a direct input of unpopulated signal. A large number of such monitorsare used to keep a check on ht contest and quality of pictures being telecast.

In addition to live studio. Video tape recording and telecoms machine rooms are located

close to the control room. In most cases, programmes as enacted in the studio are recorded onvideo tape recorder (VTR) through the control. These are later broadcast with VTR outputpassing through the same control room. All these rooms are interconnected by co-axial cablesand shielding wires.

SERVICES:

AIR has many different services each catering to different regions/languages across India. One ofthe most famous services of the AIR is the Vividh Bharati Seva (roughly translating to "Multi-Indian service"). Vividh Bharati celebrated its Golden Jubilee on 3 October 2007. Vividh Bharatihas the only comprehensive database of songs from the so termed "Golden Era" of Hindi filmmusic (roughly from 1940s to 1980s). This service is the most commercial of all and is popularin Mumbaiand other cities of India. This service offers a wide range of programmes includingnews, film music, comedy shows, etc. The Vividh Bharti service operates on different MWbandfrequencies for each city as shownbelow.

Some programs broadcast on the Vividh Bharti:

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

Santogen ki mehfil - Jokes & humour.
http://en.wikipedia.org/wiki/Mumbaihttp://en.wikipedia.org/wiki/Mumbaihttp://en.wikipedia.org/wiki/Mumbaihttp://en.wikipedia.org/wiki/Mediumwavehttp://en.wikipedia.org/wiki/Mediumwavehttp://en.wikipedia.org/wiki/Mediumwavehttp://en.wikipedia.org/wiki/All_India_Radio#Vividh_Bharati_servicehttp://en.wikipedia.org/wiki/All_India_Radio#Vividh_Bharati_servicehttp://en.wikipedia.org/wiki/All_India_Radio#Vividh_Bharati_servicehttp://en.wikipedia.org/wiki/Radio_Playhttp://en.wikipedia.org/wiki/Radio_Playhttp://en.wikipedia.org/wiki/Radio_Playhttp://en.wikipedia.org/wiki/All_India_Radio#Vividh_Bharati_servicehttp://en.wikipedia.org/wiki/Mediumwavehttp://en.wikipedia.org/wiki/Mumbai


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AIR studio set up & Doordarshan studio setup

Objectives:

To originate program from studios either for live telecast or for recording on a video tape.

To knit various other sources of programs available at the production desk - camera outputfrom studios, feed from other Kendra, outdoor, playback from pre recorded tape, videographics 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 and Microwave tothe transmitter or any other desired destinations.

STUDI O 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 f loor/ 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 associated controlling equipment

video monitors for visual feedback from the production control roomtalkback system for communication

Production control r oom:


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Video monitor : monitors for program, preview, videotape machines, cameras, graphics andother video sources

Video Switcher : a device where all video sources are controlled and taken to air.Also known as a special effects generator

Audio mixing console and other audio equipment such as effects devices

Character generator : creates the majority of the names and full screen graphics thatare inserted into the program

Master control room:

The master control room houses equipment that is too noisy. It also makes sure that wirelengths 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 andcharacter generator

Central Apparatus Room Camera control units

Audio switcher


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Studio Acoustic

Introduction

A broadcasting studio is a room in studio complex which has been specially designed andconstructed to serve the purpose of originating broadcasting programs. Whenever any musiciansings and we sit in front of a performing musician to listen to him, we enjoy the program byvirtue of the superb qualities of our sensory organs namely ears. However, when we listen to thesame program over the broadcast chain at our home though domestic receivers, the conditionsare entirely different. We as broadcasters, are continuously engaged in the task of ensuring the

maximum pleasure for the listener at home when the artists are performing inside the studios.

In order to achieve our goal we must thoroughly understand the characteristic of the differentcomponents involved in the broadcast chain, and in this process we must preserve the originalquality of sound produced by the artists inside the studio. The science of sound is often called

Acoustics. It would be thus prudent to understand the field of acoustics as applied tobroadcasting.

Acoustic Treatment

Good acoustics is a pre-requisite of high quality broadcasting or recording. Acoustic treatment isprovided in studios, control rooms, and other technical areas in order to achieve the acousticconditions which have been found from experience to be suitable for the various types ofprogrammes. In this section problems and design aspects of internal acoustics of a broadcaststudio are explained.

a) Propagation of Sound WavesSound waves emanating from a sound source are propagated in all directions. These soundwaves are subject to reflection, absorption and refraction on encountering an obstacle. Extent towhich 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 reflectedand re-reflected till the intensity weakens and it dies down.

Physical characteristics of sound waves are thus modified in various ways before they reach thehuman ear. These reflected waves can create echo effect in the room. To achieve the desirableeffects of the reflected sound, the dimensions and shape of the room are decided with due careand acoustic 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 toinaudibility.

The hanging-on of the sound in a room after the exciting signal has been removed, is calledreverberation 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 TimeR/T of a room depends upon shape and size of room and on the total absorption offered onboundary surfaces.

For a room of given volume and surface area, the R/T can be derived by Eyrings formula

R / T 0.049 V

S ln (1)

where R/T = Reverberation time in secondsV = Volume in cubic ft.S = Total surface area of room in Sq.ft. = Average absorption coefficient

Average absorption coefficient ( ) is given by

S11 S22 ......... Snn

S1S2 Sn

Where S1, S2.Sn are the areas (in sq. ft.) of different materials provided, and 1 , 2n

are the absorption coefficients of these materials. of acoustic material is defined as the ratio ofabsorbed sound to the total incident energy of sound. An open window absorbs/allows to pass allof 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 ProgrammeReverberation is the most important single parameter of a room. It influences the audio programsin 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 the flow of music.Too much of prolongation, however, may create loss in intelligibility of program due todecrease in clarity.

Reverberation time of a room is dependent on frequency. Therefore, it modifies the

frequency characteristics of the total sound field inside the room. High R/T at mid andhigh frequencies lead to increased liveness and that at low frequencies increaseswarmth. This effect can be used judiciously for desirable qualities.

e) Acoustic absorbersAcoustic absorbers are provided on the inner surfaces of the room to achieve optimum R/Tcharacteristics. Different absorbers have different absorption characteristics. No single absorbergenerally 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. Thesematerials are very good absorber and are most effective in mid and high frequencies,however, these cannot be used without some facing material.

Carpets and curtains also fall in this category.

ii) Fibrous Materials: Celotak, insulation boards, perfotiles, jolly-lowtone tiles etc. fall inthis category. Absorption of these materials depends upon their softness. Absorptionefficiency of these materials depends upon the trapping and dissipation of sound energyin tiny pores. Absorption gets reduced if the surface pores are filled with paints etc.

These materials have very poor absorption on low frequencies. However appreciableimprovement 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 of the panel and the springiness of the air in the cavity resonant at someparticular frequency.

Panel absorbers with 3mm teak ply-facing + 50mm air gap + 25mm mineral woolresonates at about 125Hz. This is generally used as low frequency absorber(LFA).

iv)Perforated Panel Absorbers: Perforated hardboard (PHB) spaced from the wall constitutea resonant type of sound absorber. The absorption can be considerably enhanced byinserting a suitable porous/fibrous damping materials in the air cavity.

The absorption pattern can be varied by adjusting the front and rear air gap from thedamping material. Absorption coefficient of these absorber depends on the percentageopen area of PHBs also.


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g) Design of Room AcousticDesign 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 isoffered by windows, doors, flooring and artists inside the studio. For the balance requirement

sound absorbing materials are provided on walls and ceiling surfaces. Calculations are generallymade at six spot frequencies of 125, 250, 500, 1000, 2000 and 4000 Hz. Quantities of materialsof known absorption coefficients are selected by trial and error method so that R/T requirementsare met within +5% of the optimum R/T at all these frequencies. Computer aided design for thesame has also been evolved. Thereafter these acoustic materials are distributed on varioussurfaces for proper diffusion of sound in the studio.


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Optical Fiber Communication

Introduction:

Fiber optics is being used to transmit television, voice, and digital data signals by lightwaves over flexible hair like threads of glass and plastic. It has evolved into a system ofgreat 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 communication systems into operation, as aresult of its performance.

Definition:

Optical Fiber Communication System converts electrical signal into light signal witch after passingthrough optical fiber cable is reconverted into electrical signal by using optical Receiver

Composit ion of optical f iber:

Silica based glass or plastic filaments are spun and packed into bundles of several hundreds orthousands. 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 aroundcorners

The thin glass center of the fiber where the light travels is called the core.

The outer optical material surrounding the core that reflects the light back into the core is called thecladding.

In order to protect the optical surface from moisture and damage, it is coated with a layer of buffercoating.


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Operat ion in opt ical f iber system:

In a fiber optic system, there are a few major components to perform the task ofcommunication.

The Input Modulator is needed; this modulates the incoming signal with a light beam.

A light emitting device is used; it can be either a light emitting diode (LED) or asemiconductor laser diode.

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 transmitsthe signal onto an optical fiber.

An Output Modulator is used to separate the signal from the light beam.

Types of optical fiber:

1.Step index:

This cable index of refraction for the core and the cladding. It causesdeformations 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 aspecific 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 fiber at the same time.Multimode dispersion is eliminated and pulse spreading is reduced. Graded Index fibercan hold the same amount of energy as multimode fiber. The disadvantage is that thistakes 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 orbitby human endeavor. Such objectsare sometimes called artificial satellites to distinguish them from natural satellites such asthe 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 likeNews & Current Affairs.

Basics of satellite communication:

Satellite basically a spacecraft placed in orbit around earth carrying microwave receive & transmitequipment on Board
http://en.wikipedia.org/wiki/Physical_bodyhttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Physical_body


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Essentially a Microwave Link Repeater Frequencies capable of passing through Ionosphere (Microwave frequencies) use Microwave frequencies permit transmission of data 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 transm it t ing device:

LNA (Low Noise Amplifier) or LNB (Low Noise Block)

LNA - amplifies RF signal from the antenna and feeds it into frequencyconverter (typically IF of 70/140 MHz)

LNB - amplifies RF signal from the antenna and converts it to an L-band signal (950-2100 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 to either C or Ku-band final frequency.


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Earthing Arrangement for a Broadcasting Station

Definition:

An Electrical connection to the general mass of earth to provide safe passage to faultcurrent to enable to operate protective devices and provide safety to personnel.

Or

The term Earthing means connecting the neutral point of a supply system or Non-currentcarrying parts of electrical apparatus to the general mass of earth in such a manner that at alltimes 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.

To allow sufficient current to flow safely for proper operation of protective devices.

To suppress dangerous potential gradients on the earth surface which may cause incorrectoperation of control & protective devices and also may cause shock or injury topersonnel.

Provide stability of voltage, prevent excessive voltage peaks duringdisturbances and protect against lightning surges.

Types of Earthing:-

Neutral Earthing : deals with the earthing of system neutral to ensure system securityand protection.

Equipment Earthing : deals with earthing of non-current carrying parts of equipment toensure safety to personnel and protection against lightning.

Danger posed to human being by electric current:

The currents, and the dangers posed to the human being, are dependent on the voltage as well ason the electrical resistance of the human body (the inner body resistance plus the skinresistances). The critical electrical voltages with which we are involved in our professional andprivate 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 dependent on the path of the current in thebody. Average values for the inner body resistance along various paths taken by the current areas follows:

Handhand 1200 ohmsHandfeet 900 ohmsHandsfeet 600 ohms


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Thus, if the voltage with which a human being comes into contact and the resistance of thehuman body are known, the intensity of the current canbe easily calculated. Further, if thecurrent intensity can be calculated, then the degree of danger posed to the human being can beassessed too.

The electrical resistivity of the earth i.e resistance of the earth to the flow of current is defined assoil resistivity Earth resistivity varies from a few ohmmeters along some sea coasts to manythousands of ohmmeters in rocky, mountainous country .

Theoretically, the resistance to remote earth of an earth electrode can be calculated. Thiscalculation 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 theconsidered area, or averaged for the local soil.

So the target of providing good earthing system is to provide least resistance path by earthelectrode of least earth resistance in a least resistivity soil.


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AM Transmitters

There are various MW AM transmitters all over the India. The SW transmitters are very fewand used for mostly international broadcasting purpose but soon will vanish. The transmissionbands 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 High level plate modulation Water or air cooled Beam power tetrodes of Ceramic/Glass tube 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 byair/water

Distilled water of low conductivity is used for HTstages


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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 300 Ohm

BLOCK DIAGRAMVOF AM TRANSM ITTER:


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FM Transmitters

The FM transmission has been developing day by day with the evolution of value added servicesand digital radio broadcasting. RDS and SCA systems are examples of it. AIR New Delhi uses asolid state 10 kW VHF FM transmitter manufactured by BEL (Bharat Electronics Ltd.) for monoand stereo. The value added services like radio traffic (RDS) and Subsidiary communicationsauthority (SCA) are now a option with the FM transmission to meet the needs of a broadspectrum of audiences and 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 TRANSM ITTER:


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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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DI VIDED 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 uppicture and sound. This place requires large space and coiling as compared to any othertechnical 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 andoperational 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 studio with lot ofmoving person and equipment during production. Supporting facilities like properties, makeupand wardrobe etc.

Digital clock display. Audio and video monitoring facilities. Pick up wall sockets for audio operations. Luminaries and suspension system having grids or battens. Tie lines box for video and audio from control room.

Cyclorama and curtain tracks for blue and black curtain for chrome keyingand 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 verticaldeflection section supplies the saw tooth current to the deflection coils of scanning the positiveimage formed on the target. The built in synchronous pulse generator provides all the pulsesrequired for the encoder and colours bar generator of the camera. The signal system in most ofthe 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 red and bluechannel is exactly similar. Green Channel, which also called a reference channel, has slightlydifferent 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 generatesynchronous 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 and tilt

head, video. Single pre- amplifier view finder and other associated electronic circuiting andmounted on cameras trolley and operate inside the studio. he output of camera of cameras inpreamplifier in the head and then connected to the camera control unit through long multi-core cable. In this room shot can be decided to which camera can be taken. Camera position

can also be control in this room. CCU can control three colourRGR= .10+.59+.11=100%

In CCU monitoring sources, monitoring facilities and pulse disribution amplifies areavailable. Vectroscope provides on overview of control and connection function. Monitor candetect any fault in the camera.

The color camera chain comprises the following basic assembly:

color camera Camera control unit Connection unit Multiwire cable

Camera view finder

The color camera chain meets the ultimate requirement in the field of studio. It featureseasy handling, operational safety and good serviceability. It can be operated either withmultiwire or with coax/triax camera cable. The color camera head, the camera control unit andremote control unit associated with the setup control console or remote control console areeach equipped with a microcomputer.

The color camera uses a 3-tube RGB system with high grade beam splitter. It isequipped with 1-inch plumbicon pickup tubes with dioxide gun system, bias light and ABCfacilities.

Various high grade lenses of different brands are available for camera. The camera control

unit is of compact design. The connection between camera head and camera control unit can beestablished either via a multiwire camera cable or via a coax/triax camera cable.

DIMM ER ROOM

Dimmer Room consists of light control system which give the various lightening effectsinthe studio.

General Description Of Light Control System :

The light control system 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 studiolamps, that need to be turned on for a particular scene & also enable control of intensity ofsome of the lamp, required for color matching.


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* Using Electronic Dimmer, the operator is able to control the intensity of lamp remotely. The intensity of a group of the lamps can be adjusted individually or in one of the two scenes.

*The system has been designed for large number of the loads, distributed on 415V,3 phase,50Hz, 4 wire mains. The phase distribution both on the rack as well as on the light control

desk are marked with dots. This helps to distribute high loads on the three phase more or lessequally.

*Any individual intensity control fader can be connected by the means of3 position lever switch to any one of the three control in each present.

SceneA OFFScene B

*Two electronic dimmer are wired as one plug in module, each rated at 2.5 KW where as onedimmer is wired in one plug in module of 5.0 KW.

*The dimmer rack is interconnected with light control desk by means of multi core 0.2qmrs. Flexible copper 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 of power todifferent racks).

L ight Control:

The scene to be television must be well illuminated to produce a clear and noise freepicture. The lighting should also give the depth, the correct contrast and artistic display ofvarious shades without multiple shadows.

The lighting arrangements in a TV studio have to be very elaborate. A large number oflights 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 anddown movement is remote controlled. The switching ON and OFF is lights at the requiredtime and their dimming 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 digital processorservo system, micro-processor, memory, logic circuits and mechanical devices etc.V.T.R


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room is provided at each studio center. It houses at least two console type 'A video taperecorders' (V.T.R.) and a few broadcast standard video cassette recorder (V.C.R.).Hererecording is done on playback format CAM. Quality of recorded programme is testedimmediately after recording is completed so that if there is any technical or any other problemthe same could be rectified and the final recording is of good quality.

During the original transmission the programme tapes are played back from the V.T.RThe audio and video labels can also be adjusted from here. The format of programme frommini D.V.C to J3 is transferred in the V.T.R room, DD news, OTR(off telecast recording) isalso recorded for the use in original news programme.

Specifications:

Video Cassette Recorders

Operational Environment1. 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 to direct 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 I nformation:

General SpecificationsPower requirements AC 90 to 265V, 48 to 68 Hz

Power consumption 240W

Operating temperature 5deg C to 40deg C

Storage temperature -20deg C to 60deg C

Humidity Less than 80%

Weight 30 Kg.Dimensions 427*237*520 mm/w/h/o

Tape speed 101.51 mm/s

Record & playback time 100 minutes max.

Fast forward/rewind time less than 180 seconds

PCR (PRODUCTION CONTROL ROOM):

The video and audio outputs are routed through a production control room. This isnecessary 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, hisassistant a camera control unit engineer a video mixer expert a sound engineer and a lightingengineer. The programme directors with the help of this staff effects overall control of theprogramme whole it is telecast live or recorded on a VTR.

The video and audio outputs from different studios and other sources are terminated

on separate panels in the control room. One panel contains the camera control unit and videomixer. In front of this panel are located a number of monitors for editing and previewing aincoming and outgoing programmes. Similarly another panel houses microphone controls.This panel is under control of the sound engineer who is consultation with the programmedirector selects and controls the available sound output.

The producer and the programme assistant have in front of them a talk back controlpanel for giving instruction to the camera man, audio engineer and floor manager. Theproducer can also talk over the intercom system to the VTR. The lighting is controlled byswitches 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

MIKETAG PATCH AUDIO

MATRIXMIKE BLOCK PANEL AMPLIFIEMIKE R

AudioDistributionAmplifier

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 notcontain vacuum tube, rather contain charged couple device CCD. CCD is compact and small insize. 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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Microphones

INTRODUCTION

Microphone is a transducer. It converts sound wave (acoustical energy) into electricalenergy.

Five important characteristics of microphone

Operating principle

Frequency response

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 andthe sound pressure on it.

Sound Pressure is applied on one side of the diaphragm. Electrical output Sound Pressure. Theoretically omnidirectional.


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Sensitivity at HF decreases. Examples Moving Coil, Carbon, crystal and Condenser

Microphones.

Pressure-operated Microphone Pressure gradient (Velocity)

Operated Microphones

2.Pressure gradient (Velocity) Operated Microphones:Both sides of diaphragm is exposed to the sound pressure. Electrical Output instantaneous difference in pressure on two sides

of diaphragm.

3.Combined-operation Microphones:The principle of pressure-operated microphones and pressure gradient operated microphones

are combined to get maximum sensitivity in one direction and minimum sensitivity in the

opposite direction.

Unidirectional characteristics.

Combined-operation Microphone


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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.

Using this electromagnet principle, the dynamic microphone uses a wire coil and magnet to createthe audio signal. The diaphragm is attached to the coil. Used in live performance 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 poles

of 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 25 V). Large diaphragm gives flattering response. Resonant frequency at the upper end 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, thisin turn induces voltage variance on 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 and rear and have null points to either side.

Cardroid Microphones:

Cardioid microphones are directional have a heart shaped polar pattern. This means they pick upsound 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 moredirectional and dont pick up as much from the side.

Omnidirectional Microphones

Bidirecti

onal Microphones


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Cardroid Microphones

Hypercardroid Microphones

SPECIAL M ICROPHONES

L ip M icrophone:

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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Lip Microphone Gun Microphone

*Gun Microphone:

Highly unidirectional Long and rod shaped.

Good for recording single voice in noisy locations.

Good for recording sound effect from a far distance.

Also used for picking up voice from long distance.

*Lapel M icrophone:

The microphone is very small and light-weight and is suspended around the neck keeping themike just below the chin.

Lapel Microphone Contact 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.

The parabolic reflector is made of sheet metal or stratified polyester

or glass fibre.

Low frequency pickup is proportional to the diameter of the reflector.

Used for recording faint sounds such as birdsongs.

Parabolic Microphone Boundary Microphone

*Boundary M icrophone:

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

receptacle.


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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 M icrophone:

These are ordinary microphones with an FM transmitter.

Provides complete freedom of movement.

Omnidirectional.

Interference from outside source.

Suitable for stage performance.

Suitable for places where laying of microphone cable is not possible.

Important character istics of microphone:

Frequency Response

Frequency response refers to the way a microphone responds to different frequencies. It is

a characteristic of all microphones that some frequencies are greater and others are attenuated

(reduced).

It depends upon:- Direction of arrival of sound and distance between the source and themicrophone.

Directivity

Microphone have directional characteristcis:

Omnidirectional:-Pick up equally at all angles.

Bidirectional:-Pick up equally from front and rear .

Unidirectional:-microphone which pick up maximum rom front .


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Sensitivity

The ability to pick up weak sound and to deliver more electrical Signal

determines the sensitivity.

Distortion

The inability to maintain linearity, resulting in the addition of unwanted HARMONICs,m

calledHarmonic 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 amount of time, called Phase Distortion

Placement of M icrophone:

a) As far as possible, microphone should be placed with its zero axis facing the source ofsound to avoid off axis colouration.

b) Phasing of microphone:-Whenever two or more microphone are used with theiroutputs 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 so asto avoid proximity effect.

d) Talking very close to a microphone may cause sound like P.

Hence it should be avoided.
http://www.sfu.ca/sonic-studio/handbook/Harmonic.htmlhttp://www.sfu.ca/sonic-studio/handbook/Transient.htmlhttp://www.sfu.ca/sonic-studio/handbook/Transient.htmlhttp://www.sfu.ca/sonic-studio/handbook/Harmonic.html


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TV TRANSMITTERS

The TV transmitters are broadly classified as:

a) H igh Power Transmitter (HPT):

TV transmitters having output power 1kW and above (1kW, 10kW, 20kW)

b) Low Power Tr ansmitter(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 30 300 kHz

MF 300 3000 kHz

HF 03 30MHZ

VHF 30 300MHZUHF 300 3000MHZ

SHF 3 30 GHZ

VHF : 30 - 300 MHz:

Band I (40-68 MHz) TV Channel 4

Channel Spacing - 7 MHz

Band II (88-108 MHz) FM Sound BroadcastingChannel Spacing - 100 KHz

Band III (174-230 MHz) CH 5 CH 12

Channel Spacing7 MHz


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UHF : 3003000 MHz:

Band IV (470606 MHz) CH 21 CH 37

Channel Spacing - 8 MHzBand V (606798 MHz) CH 38 CH 61

Channel Spacing - 8 MHz

SHF : 330 GHz:

CBand 3.7 -4.2 GHz (DL)

5.9 - 6.4 (UL)Ex. CBand 4.5 - 4.85 GHz (DL)

6.7 - 7.02 (UL)

LOW POWER TRANSMITTER CHAIN:

LNBC

TV ANTENNA

PDA RF CABLE

AudioDC

IRD EXCITER PA CH.FILTER

RF Cable Video

ORTVRO

(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 and modulated 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) housed in 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 between DMC & LPT.

Transmitter (VHF or UHF):Only one Exciter for two 500 W transmittersProtection circuits in RF stages for SafetyAgainst

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 UHF employs two 300W PAs(WEBEL)

Video/Audio 1 is Master & Video/Audio 2 is Slave Video/Audio Selectable from SCU


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CONCLUSION

The technology currently in use at Prasar Bharati has improved significantly. At this stage therehas been advancement in signal reception quality as systems have changed from analog to digitalwith the advancement in different audio and video compression techniques. For Doordarshan,DTH (Direct To Home Service) satellite services have become more user friendly and alsoevolution of SDTV into HDTV have made it a popular product among the people of India. It isalso accessible from remote areas with more channel and better reception. In AIR also, therehave been a lot of advancements being made such as transmission of more value added servicessuch as RDS, SCA, etc. These value added services have added a different taste in listeningradio.

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 familyof Prasar Bharati is growing day by day and working for the next generation broadcastingtechnique in India.

industrial training report - butola

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