INDUSTRIAL TRAINING REPORT

Submitted in the Partial Fulfillment for the Award of the Degree

Of

Bachelor of Technology In

Electronics and Communication Engineering.

NORTH EASTERN REGIONAL INSTITUTE OF

SCIENCE AND TECHNOLOGY

NIRJULI::791109

ARUNACHAL PRADESH

SUBMITTED To:- SUBMITTED By:-

H. O. D. RAJUL KUMAR PANDEY

Electronics and Communication DE-09-EC-06

NERIST BIRAJ CHITROKAR

DE-09-EC-32

31st MAY – 20

th JULY, 2010

ACKNOWLEDGEMENT

This report is an outcome of the practical training which I have gone through at

Prasar Bharti Doordarshan (Broadcasting Corporation of India) Staff

Training Institute (Technical) Kingsway Camp, Delhi - 110009.

I would like to express deep sense of gratitude towards Mr. N. A. Khan,

Director, STI(T) who permitted us to undergo 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)

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 an

opportunity 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 Prasar Bharti Doordarshan.

CERTIFICATE

This 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 9

th 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 Mr. N.A. Khan

Assistant Director Director

STI (T) STI (T)

Kingsway Camp, Delhi Kingsway Camp, Delhi

CERTIFICATE

This 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

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 9

th 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 Mr. N.A. Khan

Assistant Director Director

STI (T) STI (T)

Kingsway Camp, Delhi Kingsway Camp, Delhi

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

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 ............................................................................................................................................... 2

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

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

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

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

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

Studios and 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 to AIR ........................................................................................................................... 5

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 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 rd year ,the company went into liquidation on 1st march,1930

.

It locked as through introduction 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 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.controlle of broadcasting constitude

8June, 1936 India state broadcasting service become All India Radio

Nov, 1937 AIR comes under the dept. of comm..

23Feb, 1946 AIR comes under info & arts.

1947 six radio station in India

Delhi

Bombay

Calcutta

Madras

Tiruchirapalli

Lucknow

After Independence:

20 july, 1952 first national programmers of music broadcast from

AIR.

29 april, 1953 national programmers of talks commence from AIR

3 oct, 1957 Vividh Bharti service started.

1959 first TV station in Delhi

Purpose of the constitution of All India Radio:

For the efficient supervision of programmer and for maintains of high standards in

several type of broadcasting.

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. 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 medium of

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 education,

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

INTRODUCTION

Prasar 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 the proliferation 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 foreign

languages.

All India Radio (abbreviated as AIR), officially known as Akashvani is the radio broadcaster of

India and a division of Prasar Bharati Act provides for establishment of April 1930 Broadcasting

was placed under the direct control of Government under the title 'Indian State Broadcasting

Service' (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 in

Mysore 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 section

and the National service. The Doordarshan Kendra (Delhi) is also located on the 6th

floor of

Akashvani Bhavan.

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 televised Several cameras

are used to telecast the scene from different angles. Similarly a large number of

microphones are provided at different locations to pick up sound associated with

programme.

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 signals

but operates on a direct input of unpopulated signal. A large number of such monitors

are 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 on

video tape recorder (VTR) through the control. These are later broadcast with VTR output

passing through the same control room. All these rooms 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 "Multi-

Indian 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 operates on 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.

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

output from studios, feed from other Kendra, outdoor, playback from 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 and

Microwave 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 recorded

take 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 room

talkback system for communication

Production control room:

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

Audio mixing 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

Studio Acoustic

Introduction

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 sensory organs 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 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 different

components involved in the broadcast chain, and in this 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 be thus prudent to understand the field of acoustics as applied to

broadcasting.

Acoustic Treatment

Good acoustics is a pre-requisite of high quality broadcasting or recording. Acoustic treatment is

provided in studios, control rooms, and other technical areas in order to achieve the acoustic

conditions which have been found from experience to be suitable for the various types of

programmes. In this section problems and 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 thus modified in various ways before they reach the

human ear. These reflected waves can 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

and acoustic treatments are also provided on the various surfaces.

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/T can be derived by Eyring‟s formula

)1(lnS

V049.0T/R

where R/T = Reverberation time in seconds

V = Volume in cubic ft.

S = Total surface area of room in Sq.ft.

= Average absorption coefficient

Average absorption coefficient ( ) is given by

n21

nn2211

S.......SS

S.........SS

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 defined 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

Reverberation is the most important single parameter of a room. It influences the audio

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.

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 to

decrease 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 and

high frequencies lead to increased „liveness‟ and that at low frequencies increases

„warmth‟. This effect can be used judiciously for desirable qualities.

e) Acoustic absorbers

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

materials 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 in

this category. Absorption of these materials 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 of the 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 in the 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.

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 Eyring‟s 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 on walls 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. Computer aided 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.

Optical Fiber Communication

Introduction:

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 1980‟s.

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 a

result of its performance.

Definition:

Optical Fiber Communication System converts electrical signal into light signal witch after

passing through optical fiber cable is reconverted into electrical signal by using optical Receiver

Composition of optical fiber:

Silica based glass or plastic filaments 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”.

The outer 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.

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

semiconductor 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

transmits the 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 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 fiber at 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

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

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 Earth‟s 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 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.

Earthing Arrangement for a Broadcasting Station

Definition:

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 a supply 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.

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 incorrect

operation of control & protective devices and also may cause shock or injury to

personnel.

Provide stability of voltage, prevent excessive voltage peaks 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 posed to human being by electric current:

The currents, and the dangers posed to the human 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 critical 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 dependent on 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

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 coasts to 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.

AM Transmitters

There are various MW AM transmitters all over the India. The SW transmitters are very 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 High level plate modulation

Water or air cooled

Beam power tetrodes of Ceramic/Glass tube

Directly heated cathode

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

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 TRANSMITTER:

FM Transmitters

The 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 by BEL (Bharat Electronics Ltd.) for mono

and stereo. The value added services like radio traffic (RDS) and Subsidiary communications

authority (SCA) are now a option with the FM transmission to meet the needs of a broad

spectrum of audiences and the emergence of new multimedia forms.

Following is the list of BEL‟s FM transmitters‟ installation in India.

BLOCK DIAGRAM OF 2*3kW FM TRANSMITTER:

The FM antenna has been shown below:

A typical FM Mast:

Activities in TV Studio

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 studio with 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.

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 keying and

limbo lighting respectively.

Camera Chain:

A typical three tube camera chain is described in the block diagram. Tube power

supply 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 synchronous 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 red and 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:

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 and

mounted on cameras trolley and operate inside the studio. he output of camera of cameras in

preamplifier 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 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

detect 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 features

easy handling, operational safety and good serviceability. It can be operated either with

multiwire or with coax/triax camera cable. The color camera head, the camera control unit

and remote control unit associated with the setup control console or remote control console

are each equipped with a microcomputer.

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 brands are available for camera. The camera control

unit is of compact design. The connection between camera head and camera control unit can be

established either via a 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 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 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.

* 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 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 is interconnected with light control desk by means of multi core 0.2 qmrs.

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 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 very elaborate. 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 remote controlled. The switching ON and OFF is lights at the required

time 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 processor

servo system, micro-processor, memory, logic circuits and mechanical devices etc.V.T.R

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 is any technical or any other problem

the 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.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 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 Information:

General Specifications

Power 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 is

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

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 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 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 the sound 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

Mon.

O/P

Studio AUDIO CONSOLE UNIT VTR

ENG-CAMERA:

MATRIX TAG

BLOCK

PATCH

PANEL

AUDIO

AMPLIFIE

R

Audio

Distribution

Amplifier

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.

Microphones

INTRODUCTION

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

energy.

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

and the sound pressure on it.

Sound Pressure is applied on one side of the diaphragm.

Electrical output α Sound Pressure.

Theoretically omnidirectional.

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 α 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

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 create the 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.

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

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 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

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 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 don‟t pick up as much from the side.

Omnidirectional Microphones

Bidirecti

onal Microphones

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.

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 Microphone:

• The microphone is very small and light-weight and is suspended around the neck keeping the

mike just below the chin.

Lapel Microphone Contact Microphone

*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 Microphone :

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

receptacle.

• 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 freedom of 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 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 the

microphone.

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 .

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

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 amount of time, called Phase Distortion

Placement of Microphone:

a) As far as possible, microphone should be placed with its zero axis facing the source 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 so as

to avoid proximity effect.

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

Hence it should be avoided.

TV TRANSMITTERS

The 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 to 50W

(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 300MHZ

UHF 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 Broadcasting

Channel Spacing - 100 KHz

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

Channel Spacing – 7 MHz

UHF : 300 – 3000 MHz:

Band IV (470 – 606 MHz) CH ≠ 21 – CH ≠ 37

Channel Spacing - 8 MHz

Band V (606 – 798 MHz) CH ≠ 38 – CH ≠ 61

Channel Spacing - 8 MHz

SHF : 3 – 30 GHz:

C – Band 3.7 - 4.2 GHz (DL)

5.9 - 6.4 (UL)

Ex. C – Band 4.5 - 4.85 GHz (DL)

6.7 - 7.02 (UL)

LOW POWER TRANSMITTER CHAIN:

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

OR

TVRO (SATELLITE RECEIVER)

LNBC

PDA

IRD

Audio

Video

TV ANTENNA

RF Cable

EXCITER PA CH.FILTER

DC

RF CABLE

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 transmitters

Protection circuits in RF stages for Safety

Against

1. VSWR

2. Thermal & Excess power faults to

prevent failure of RF devices

Both Transmitters are Micro controller Based

Remotely Controllable

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

CONCLUSION

The technology currently in use at Prasar Bharati has improved significantly. At this 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 HDTV have made it a popular product among the people of India. It is

also accessible from 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.