mohitReport Amity

8/11/2019 mohitReport Amity

1/32


2/32

2

2. TV SYSTEM

Picture formation: -

A picture can be considered to contain a number of small elementary areas of light orshade which are called PICTURE ELEMENTS. The elements thus contain the visual

image of the scene.In the case of a TV camera the scene is focused on the photosensitive surface

of pick up device and a optical image is formed. The photoelectric properties of thepick up device convert the optical image to a electric charge image depending on thelight and shade of the scene (picture elements). Now it is necessary to pick up thisinformation and transmit it. For this purpose scanning is employed. Electron beamscans the charge image and produces optical image. The electron beam scans theimage line by line and field by field to provide signal variations in a successive order.

The scanning is both in horizontal and vertical direction simultaneously.The horizontal scanning frequency is 15,625 Hertz.

The vertical scanning frequency is 50 Hz.

The frame is divided in two fields. Odd lines are scanned first and then the even lines.The odd and even lines are interlaced. Since the frame is divided into 2 fields theflicker reduces. The field rate is 50 Hertz. The frame rate is 25 Hertz (Field rate is thesame as power supply frequency).

Number of TV Lines per Frame:-

If the number of TV lines is high larger bandwidth of video and hence larger R.F.channel width is required. If we go for larger RF channel width the number of channelsin the R.F. spectrum will be reduced. However, with more no. of TV lines on the screenthe clarity of the picture i.e. resolution improves. With lesser number of TV lines perframe the clarity (quality) is poor.

The capability of the system to resolve maximum number of picture elements alongscanning lines determines the horizontal resolution. It means how many alternate blackand white elements can be there in a line. Let us also take another factor. It is realisticto aim at equal vertical and horizontal resolution. Therefore, the number of alternate

black and white dots on line can be 575 x 0.69 x 4/3 which is equal to 528.It means there are 528 divided by 2 cyclic changes i.e. 264 cycles. These 264 cyclesare there during 52 micro seconds. Hence the highest frequency is 5 MHz.

Therefore the horizontal resolution of the system is 5 MHz.A similar calculation for525 lines system limits the highest frequency to 4 MHz and hence the horizontal


3/32

3

resolution of same value.In view of the above the horizontal bandwidth of signal in 625 lines system is 5 MHz.

The PAL Colour Television System:-

The Colour Television:-It is possible to obtain any desired colour by mixing three primary colours i.e. Red,

Blue and green in a suitable proportion.

Additive Colour Mixing

The figure 10 shows the effect of projecting red, green, blue beams of light so that theyoverlap on screen.

Y= 0.3 Red + 0.59 Green + 0.11 Blue

F ig. 10 Additi ve Colour M ixing

The Colour Television

It is possible to obtain any desired colour by mixing three primary colours i.e., red,blue and green in suitable proportion. Thus it is only required to convert opticalinformation of these three colours to electrical signals and transmit it on differentcarriers to be decoded by the receiver. This can then be converted back to the opticalimage at the picture tube. The phosphors for all the three colours i.e. R, G and B areeasily available to the manufacturers of the picture tube. So the pick up from thecameras and output for the picture tube should consists of three signals i.e. R, G and B.It is only in between the camera and the picture tube of the receiver we need a systemto transmit this information.


4/32

4

Colour television has the constraint of compatibility and reverse compatibility with themonochrome television system which makes it slightly complicated. Compatibilitymeans that when colour TV signal is radiated the monochrome TV sets should alsodisplay Black & White pictures. This is achieved by sending Y as monochromeinformation along with the chroma signal. Y is obtained by mixing R,G & B as per thewell known equation :

Y = 0.3 R + 0.59 G + 0.11 B

Reverse compatibility means that when Black & White TV signal is radiated the colourTV sets should display the Black & White pictures.

If we transmit R, G, B, the reverse compatibility cannot be achieved. Let us see how :

If we transmit Y, R & B and derive G then :Since Y = 0.3R + 0.59G + 0.11 B

G = 1.7Y - 0.51 R - 0.19 B

In such a case what happens with a colour TV set when we transmit black and whitesignal. R and B are zero, but G gun gets 1.7 Y. The net result is black & white pictureson a colour TV screen appear as Green pictures. So reverse compatibility is notachieved.


5/32

5

3. TV LIGHTING

GENERAL PRINCIPLES

Lighting for television is very exciting and needs creative talent. There is always atremendous scope for doing experiments to achieve the required effect. Light is a kind

of electromagnetic radiation with a visible spectrum from red to violet i.e. wave lengthfrom 700 nm to 380 nm respectively. However to effectively use the hardware andsoftware connected with lighting it is important to know more about this energy.

Light SourceAny light source has a Luminance intensity (I) which is measured in Candelas. Candelais equivalent to an intensity released by standard one candle source of light.

Basic Three Point Lighting

Key light :This is the principal light source of illumination. It gives shape andmodeling by casting shadows. It is treated like "sun" in the sky and it should castonly one shadow. Normally it is a hard source.Fill Light :Controls the lighting contrast by filling in shadows. It can also providecatch lights in the eyes. Normally it is a soft source.Back light :Separates the body from the background, gives roundness to the subjectand reveals texture. Normally it is hard source.Background Light :Separates the person from the background, reveals backgroundinterest and shape. Normally it is a hard source.In three point lighting the ratio of3/2/1 (Back/Key/Fill) for mono and 3/2/2 for colour provides good portrait lighting.

TV CAMERA:-

Introduction

A TV Camera consists of three sections :a) A Camera lens and optics : To form optical image on the face

plate of a pick up device.b) A transducer or pick up device : To convert optical image into an

electrical signal.

c) Electronics : To process output of a transducer toget a CCVS signal.

CCD CAMERAS

Introduction

Any camera will need a device to convert optical image into an electrical signal. Nowlet us consider a picture frame made of small picture element. For more sharpness or

better resolution we have to increase these elements. This picture frame can now be

focused on to a structure of so many CCD elements. Each CCD element will nowconvert the light information on it to a charge signal. All we need now is to have an


6/32

6

arrangement to collect this charge and convert it to voltage. This is the basic principleon which CCD cameras are based.

Latest CCD CamerasCCD were launched in 1983 for broadcasting with pixel count from a mere 2,50,000which increased to 20,00,000 in 1994 for HDTV application. Noise and aliasing has

been reduced to negligible level. CCD cameras now offers fully modulated videooutput at light level as low as 6.0 lumens. A typical specification for a studio cameranow available in market are some thing like 2/3 inch, FIT, lens on chip CCD with6,00,000 pixel, 850 lines H resolution, S/N more than 60 dB, sensitivity F-8 (2000 lux)etc.


7/32

7

4. Modulation

Modulation is a technique in which message signal is transmitted to the receiver withthe help of carrier signal. Here in modulation, we combine both carrier signal andmessage signal.

Advantages of M odulation:

With the help of modulation, we can increase the quality of reception. We can also decrease the height of the antenna.

Avoid mixing of different frequency signals and increase the range of

communication i.e. without modulation, we can transmit the message up to 100meters and with modulation, we can transmit the message up to 150 meters.

Allow the flexibility for adjusting the bandwidth.

Angle Modulation:In the angle modulation, again there are two different types of modulations.

1. Frequency modulation2. Phase modulation.

1. F requency Modulation:

The process of carrier signal frequency is varied according to the message signal ormodulation signal frequency by keeping the amplitude constant is called frequencymodulation.

Advantages of f requency modulati on

Resilient to noise Resilient to signal strength variations

Does not require linear amplifiers in the transmitter

Disadvantages of f requency modulation


8/32

8

Requires more complicated demodulatorSome other modes have higher data spectral efficiencySidebands extend to infinity either side

Applications of F requency Modulation (FM ):

Frequency modulation is used in radios which is very common in our daily

life. Frequency modulation is used in audio frequencies to synthesize sound.

For recording the video signals by VCR systems, frequency modulation is usedfor intermediate frequencies. Used in applications of magnetic tape storage

2. Phase Modulation:In the phase modulation, we vary the carrier signal in accordance with the phase ofthe modulating signal or message signal by keeping the frequency constant. If the

amplitude of message or modulating signal is huge then the phase shift will also begreater.

Advantages and Disadvantages of Phase Modulation:

It has less interference from static, which is why we use this type of modulationin finding out the speed or velocity of a moving object. The main disadvantage is phase ambiguity comes if we increase the phase

modulation index, and data loss is more and we need special equipment likefrequency multiplier for increasing the phase modulation index

Appli cations of Phase Modulation:

Phase modulation application is not different from frequency modulation.Phase modulation is also used in communication systems. It may be used in binary phase shift keying.

Ampli tude Modulation:

In the amplitude modulation, amplitude of carrier signal wave is varied in accordancewith the modulating or message signal by keeping the phase and frequency of the

signals constant.

Applications of Ampli tude Modulation:

Used to carry message signals in early telephone lines. Used to transmit Morse code using radio and other communication systems. Used in Navy and Aviation for communications as AM signals can travel

longer distances. Widely used in amateur radio.


9/32

9

ADVANTAGES DISADVANTAGES

It is simple to implement It can be demodulated using a

circuit consisting of very fewcomponents

AM receivers are very cheap asno specialised components are needed.

An amplitude modulation signal is notefficient in terms of its power usage

It is not efficient in terms of its use ofbandwidth, requiring a bandwidth equal to

twice that of the highest audio frequency

An amplitude modulation signal isprone to high levels of noise becausemost noise is amplitude based andobviously AM detectors are sensitiveto it.


10/32

10

5. Satellite communication

What is satell i te:A satelliteis anobject which has been placed intoorbitbyhuman endeavor. Suchobjects are sometimes called artificial satellitesto distinguish them fromnaturalsatellites such as theMoon.

Purpose of satel l i te 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 programmeslike News & Current Affairs.

Basics of satell i te communication:

Satellite basically a spacecraft placed in orbit around earth carrying microwavereceive & transmit equipment on Board

Essentially aMicrowave Link Repeater

Frequencies capable of passing through Ionosphere (Microwave frequencies) use

Microwave frequencies permit transmission of data at high rate.

Reason of satell i te 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
http://en.wikipedia.org/wiki/Physical_bodyhttp://en.wikipedia.org/wiki/Physical_bodyhttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Moonhttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Physical_body


11/32

11

Receving and transmi tting 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 i s more precise and stable but more expensive than LNB (LO stabil i ty).

Transmit power amplifiers provide amplification of signals to be transmitted to thesatellite

Transceiver takes 70/140 MHz signal and amplifies it to either C or Ku-band finalfrequency.

Block Up-Converter takes L-band signal and amplifies it to either C or Ku-band finalfrequency.


12/32

12

India and Satellite Communication Systems

India first experimented with geosynchronous telecommunications relays in 1981 andnow has three active spacecraft in GEO. Moreover, the launch of INSAT 2A in July,1992, marked the debut of India's first domestically built operational GEO space-craft. In a departure from most nations, India's GEO platforms combine a

communications mission with that of Earth observation.

APPLE

INSAT 1

INSAT 2

INSAT 3

ASC Network

India undertook the Satellite Instructional Television Experiment (SITE) in 1975-76to telecast a series of educational programs on health, family planning, agricultureand the like to over 2,500 Indian villages via the US satellite, ATS-6. It was thelargest sociological experiment ever carried out in the world. The SatelliteTelecommunication Experimental Project (STEP), conducted using Franco-GermanSymphonie satellite during 1977-79, was another major demonstration ofcommunication applications of space.

India has registered an impressive growth in the telecom sector. Over the years thecountry has developed a vast telecom network comprising over 25000 telephoneexchanges and 21.5 million working connections. There is a large network of opticalfibre cables, digital microwave and satellite communication systems. A very strongindustrial base has been built in the telecom sector with a large number of nationaland multinational telecom companies.

A number of policy changes have been made in the recent past which, ifimplemented, are bound to have a significant impact on the telecom scenario. The

most significant among the changes is the announcement of a New Telecom Policy(NTP) 1999. The policy envisages development of telecom facilities in remote, ruraland tribal areas of the country and their availability to the masses at affordable costs.The NTP 1999, which has come into effect from April 1, 1999, aims at makingtelephones available on demand by the year 2002 and to achieve teledensity of seven

per hundred persons by the year 2005. In case of rural areas, the current teledensity isproposed to be raised from 0.4 to 4 by the year 2010. The policy document of NTPoutlines rapid growth in the telecom sector in India with a projected teledensity of 15

by the year 2010. This will require a massive investment of over 23 billion dollars inthe next five years.
http://fas.org/spp/guide/india/comm/apple.htmhttp://fas.org/spp/guide/india/comm/insat1.htmhttp://fas.org/spp/guide/india/comm/insat2.htmhttp://fas.org/spp/guide/india/comm/insat3.htmhttp://fas.org/spp/guide/india/comm/asc.htmhttp://fas.org/spp/guide/india/comm/asc.htmhttp://fas.org/spp/guide/india/comm/insat3.htmhttp://fas.org/spp/guide/india/comm/insat2.htmhttp://fas.org/spp/guide/india/comm/insat1.htmhttp://fas.org/spp/guide/india/comm/apple.htm


13/32

13

6. High POWER TV TRANSMITTERS

Design:-

All the TV transmitters have the same basic design. They consist of an exciter followed

by power amplifiers which boost the exciter power to the required level.

Exciter:-

The exciter stage determines the quality of a transmitter. It contains pre-corrector unitsboth at base band as well as at IF stage, so that after passing through all subsequenttransmitter stages, an acceptable signal is available. Since the number and type ofamplifier stages, may differ according to the required output power, the characteristicsof the pre-correction circuits can be varied over a wide range.

Vision and Sound Signal Amplification:-In HPTs the vision and sound carriers can be generated, modulated and amplifiedseparately and then combined in the diplexer at the transmitter output.In LPTs, on the other hand, sound and vision are modulated separately but amplified

jointly. This is common vision and aural amplification.A special group delay equalization circuit is needed in the first case because of errors

caused by TV diplexer. In the second case the intermodulation products are moreprominent and special filters for suppressing them is required.

As it is difficult to meet the intermodulation requirements particularly at higherpower ratings, separate amplification is used in HPTs though combined amplificationrequires fewer amplifier stages.Power Amplifier Stages

In BEL mark I & II transmitters three valve stages (BEL 450 CX, BEL 4500 CX andBEL 15000 CX) are used in vision transmitter chain and two valves (BEL 450 CX andBEL 4500 CX) in aural transmitter chain. In BEL mark III transmitter only two valvestages (BEL 4500 CX and BEL 15000 CX) are used in vision transmitter chain. Auraltransmitter chain is fully solid state in Mark III transmitter.BEL 10 kW TV TRANSMITTER

A block diagram of BEL 10 kW TV Transmitter is shown in Fig. 10. It consists of :

a)

Input Equipment Rackb) Monitoring Equipment Rackc) Control Consoled) Indoor Co-axial Equipment comprising of :

U-link Rack with U-link panel A and B, T-Transformer and 10 kWDummy Load.

Aural Harmonic Filter.

CIN Diplexer

Aural Notch Filter and Band Pass Filter.

e)

Antenna system with junction box, feeder cables etc.


14/32

14

Block Diagram of 10kW TV Transmitter

SOLID STATE POWER AMPLIFIERS

1) Has got two identical sections. Each capable of delivering 10 W.2) Gets 28 V power supply through relay in 80 W AMP.3) Sample of output is available at front panel for RF monitoring.4) Provides A DC output corresponding to sync peak out put for vision monitoring

unit.

5)

Thermostat on heat sink is connected in series with thermostat or 80 W AMPand provides thermal protection. (Operating temp. 70oC.)

TX. Block Diagram


15/32

15

Vision Chain of Exciter

TRANSMITTER CONTROL SYSTEM:-

The transmitter control unit performs the task of transmitter interlocking and control.Also it supports operation from control console. The XTR control unit (TCU) has twoindependent system viz.1. Main control system. (MCS)2. Back-up Control System (BCS)

System Description of Exciter :

Video Chain:-The input video signal is fed to a video processor. In VHF transmittersLPF, Delay equalizer and receiver pre-corrector precede the video processor.

Low Pass Filter : Limits incoming video signal to 5 MHz.

Delay Equalizer : Group delay introduced by LPF is corrected. It also pre-distortsthe video for compensating group delay errors introduced in the subsequent stages anddiplexer.

Receiver pre-corrector :Pre-distorts the signal providing partial compensation of GDwhich occurs in domestic receivers.Both the delay equaliser and receiver precorrector

are combined in the delay equaliser module in Mark III version.DP/DG Corrector

This is also used in the exciter preceding LPF (mark III) for pre-correcting thedifferential gain and differential phase errors occurring in the transmitter.

Video Processor

The block diagram of video processor is given in fig. 3.Functions

Amplification of Video signal

Clamping at back porch of video signal.Clamping gives constant peak power. Zero volt reference line is steady irrespective of


16/32

16

video signal pattern when clamping takes place otherwise the base line starts anexcursion about the zero reference depending on the video signal.

Block Diagram of Video Processor

Vision Modulator

The block diagram of Vision modulator is given in fig. 4 and schematic diagram is

shown in fig. 5Functions

Amplification of Vision IF at 38.9 MHz.

Linear amplitude modulation of Vision IF by video from the video processor ina balanced modulator.

IF Amplifier

IF is amplified to provide sufficient level to the modulator. It operates as an amplitudelimiter for maintaining constant output.

Modulator

A balanced modulator using two IS-1993 diodes is used in the modulator.

Band pass amplifierModulated signal is amplified to 10 mW in double tuned amplifier which provides aflat response within 0.5 dB in 7 MHz band.

VSBF and Mixer :

The block diagram of VSBF and Mixer is given in fig. 6. It consists of followingstages :

VSB filter

ALC amplifier

Mixer

Helical Filter

Mixer Amplfier


17/32

17

Block Diagram of VSBF Mixer

VSB Filter

Surface Acoustic wave (SAW) filter provide a very steep side band response with highattenuation outside designated channel. It has a linear phase characteristic with a low

amplitude and group delay ripple. (Fig. 7.)

Block Diagram of V.S.B.Filter

.

Local Oscillator

It supplies three equal outputs of + 8 dBm each at a frequency of fv + fvif. This unit

has 3 sub units.(1) fc/4 oscillator : Generates frequency which is 1/4 of desired channel frequency.

Fine freq. control is done by VC1.(2) LO Mixer/Power divider : Here the above fc/4 frequency is multiplied by four

to obtain channel frequency of fc and then mixed with fvif. Power divider isalso incorporated to provide three isolated outputs of equal level.

Block Diagram of Local Oscillator


18/32

18

7. Microphones

I. How They Work.

A microphone is an example of a transducer, a device that changes information fromone form to another. Sound information exists as patterns of air pressure; the

microphone changes this information into patterns of electric current.

A variety of mechanical techniques can be used in building microphones. The twomost commonly encountered in recording studios are the magneto-dynamic and thevariable condenser designs.

THE DYNAMIC MICROPHONE.

In the magneto-dynamic, commonly called dynamic, microphone, sound waves causemovement of a thin metallic diaphragm and an attached coil of wire. A magnet

produces a magnetic field which surrounds the coil, and motion of the coil within thisfield causes current to flow. The principles are the same as those that produceelectricity at the utility company, realized in a pocket-sized scale. It is important to

remember that current is produced by the motion of the diaphragm, and that theamount of current is determined by the speed of that motion. This kind of microphone


19/32

19

is known as velocity sensitive.

THE CONDENSER MICROPHONE.

In a condenser microphone, the diaphragm is mounted close to, but not touching, arigid backplate. (The plate may or may not have holes in it.) A battery is connected to

both pieces of metal, which produces an electrical potential, or charge, between them.The amount of charge is determined by the voltage of the battery, the area of thediaphragm and backplate, and the distance between the two. This distance changes asthe diaphragm moves in response to sound. When the distance changes, current flowsin the wire as the battery maintains the correct charge. The amount of current isessentially proportioinal to the displacement of the diaphragm, and is so small that itmust be electrically amplified before it leaves the microphone.

OTHER TYPES


20/32

20

8. DRM- Digital Radio Mondiale

What is DRM?The DRM Broadcasting system has been designed by broadcasters, for broadcasters,

but with the active assistance and participation of both transmitter and receiver

manufacturers and other interested parties (such as regulatory bodies). It has beendesigned specifically as a high quality digital replacement for current analogue radio

broadcasting in the AM and FM/VHF bands; as such it can be operated with the samechannelling and spectrum allocations as currently employed.

The DRM standard describes a number of different operating modes, which may bebroadly split into two groups as follows:

DRM30 modes, which are specifically designed to utilise the AM broadcast bandsbelow 30 MHz, and

DRM+ modes, which utilise the spectrum from 30 MHz to VHF Band III, centredon the FM broadcast Band II

Digital Migration

The DRM system was specifically designed to align with and make use of currentanalogue spectrum allocations to co-exist with current analogue broadcasts2. Thisallows broadcasters to make the required investment on a timescale that meets their

budgetary needs. It will ensure that expensively acquired and perfectly satisfactorytransmission equipment and infrastructure is not suddenly made obsolete. Suitable

analogue transmitters can be modified to switch between digital and analoguebroadcasts, further reducing the initial investment required for a broadcaster wishingto migrate to DRM. This in turn allows broadcasters to focus their capital resources onnew content and services. Additionally, the reduction of the transmitting energy costsallows additional revenue savings, which can be ploughed back into programming.

Apart from the ability to fit in with existing spectrum requirements, the DRM systemalso benefits from being an open system, allowing any manufacturer to design and

manufacture equipment on an equitable basis. This has proved, in the recent past, to bean important mechanism for ensuring the timely introduction to market of new systemsand for accelerating the rate at which equipment prices reduce. This is a significantconsideration for broadcasters but even more so for the millions of listeners who will


21/32

21

need to invest in new, DRM-capable receivers.

BENEFI TS of DRM

So what can digital radio offer that is not available already in the analogue world?

From a listeners perspective digital means a wider choice of stations, languages andcontent, (while not losing the analogue offer). The sound is also better as you can enjoyhiss and crackle-free digital quality sound not only in FM but also in short wave andmedium wave. In effect digital sound becomes high quality in all bands,nomatter if you listen to a faraway broadcaster or your local station. Also there is no morefiddling with buttons and trying to remember frequencies .You simply have to push a

button and your chosen station follows you like a faithful pet, not the other way round.You get to your favourite station just by choosing its name, simple!

Digital radio also give you access to digital features like information on what you arelistening to, whether ge nerated by the radio station or from the internet, pictures,video, content in several languages simultaneously, emergency warning in case ofdisaster and so much more.

DRM+ system is also capable of transmitting 5.1 surround sound signals to enableradio listeners to enjoy the same quality as listening in a cinema theatre.

DRM is a cost efficient solution all along the value chain. It uses spectrum moreefficiently, offers extra opportunities for revenue generation and uses less power (by

at least a third) so it is a genuinely greenoption.

Digital radio is about making exciting, multi- lingual content available and socompelling that the listener will want to acquire a new digital receiver, whether it will

be a new funky standalone, a car one or a di gital enabler in mobiles , PDAs or tablets.

And broadcasters, manufacturers, regulators and all supporters of digital radio

have to be ready with a credible and affordable offer. Having chosen DRM 30 for

the medium wave and short wave transmissions the natural step for India is toopt for DRM+ in FM. There is no either or between FM and DRM+. A careful

and wise rollout plan will help with the introduction of digital VHF in a planned

and economical way.


22/32

22

9.Digital Video Broadcasting-T2

DVB-T2 is the next development of the Digital Video Broadcasting - Terrestrial

standards. It builds on the technology and on the success of DVB-T to provide

additional facilities and features in line with the developing DTT or Digital

Terrestrial television market.Although some may see DVB-T2 as a competitor to the existing DVB-T standard,

this is not the case,. It is planned that the two standards will co-exist for many

years, with DVB-T2 allowing additional features and services.

DVB-T2 basics


23/32

23

The Reception mode of dvb t2 transmission. Note that it is multi device

transmibility as many devices of different types like mobiles, tv , laptops, in cars

and buses we can see the tv transmission.The DVB-T2 standard uses Orthogonal Frequency Division Multiplex as the basicradio transmission medium. This form of transmission is particularly robust and allowsfor the reception of data signals (in this case television data) in the presence of someinterference or missing channels as a result of effects like multipath.


24/32

24

10. EARTH STATION TECHNOLOGIES

The advantage of satellite technology is based on the potential for reaching wide

expanses and serving discontinuous user bases without the cost of traditional terrestrialservices (i.e., multiple central offices, microwave hops, repeaters, etc). Therefore, the

earth station becomes a critical factor in the design of satellite systems. Technological

advances in the area of earth station equipment improvement has been a continuing

focus for satellite system manufacturers. The more technology can be improved and

costs reduced, the greater the potential for the future of satellite communications.

There are currently three classes of earth stations:

Mass capacity station--Designed for large users or inter-exchange carrier applications.

This type of earth station serves a user community with communications needs great

enough to require feeder line access to the earth station. The cost for earth stations in

this class runs into millions of dollars.

Middle range earth station--Designed for large corporate applications. This type of

earth station serves a single large user (e.g. newspaper publisher, financial institution,

etc). The cost for earth stations in this class run into the hundreds of thousands of

dollars.

Low-end earth station--Designed for smaller corporate applications. This type of

earth station serves a single user (e.g., retailers, general business, etc) and is typically

designed to handle data traffic (e.g., point-of-sale information, inventory control, credit

authorization, and other types of remote processing). These types of earth stations are

established with a minimal amount of equipment and a very small aperture terminal

(VSAT).

Each VSAT site is equipped with a terminal consisting of an antenna (varying in

size from 1.2 to 1.8 meters in diameter), outdoor electronics mounted on or near the


25/32


26/32

26

11. 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 technicalarea. Action in this area includes staging, lighting performance by artists andarrangement to pick up picture and sound. This place requires large space and coilingas compared to any other technical data. Very efficient air conditioning because oflot 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 amultipurpose studio with lot of moving person and equipment during production.Supporting facilities like properties, makeup and wardrobe etc.

(i) Digital clock display.(ii) Audio and video monitoring facilities.(iii) Pick up wall sockets for audio operations.(iv) Luminaries and suspension system having grids or battens.

(v)

Tie lines box for video and audio from control room.Cyclorama and curtain tracks for blue and black curtain for chrome keying and limbolighting respectively.

Camera Chain :

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

synchronous pulse generator provides all the pulses required for the encoder andcolours bar generator of the camera. The signal system in most of the camera consistsof processing of the signal form red, blue and green tube. Some of the camera us-ewhite, 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, hasslightly different electronics concerning aperture correction. So if we understand a

particular channel, the other channels can be followed easily. In each camera signalare given to generate synchronous pulse and black burst pulse for a good picture intelevision.

Camera control unit:


27/32

27

The TV camera which includes camera head with its optical focusing lens. panand tilt head, video. Single preamplifier view finder and other associatedelectronic 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 tothe camera control unit through long multi-core cable. In this room shot can bedecided to which camera can be taken. Camera position can also be control in thisroom. CCU can control three colour

RGR= .10+.59+.11=100%

In CCU monitoring sources, monitoring facilities and pulse disributionamplifies are available. Vectroscope provides on overview of control andconnection function. Monitor can detect any fault in the camera.

The color camera chain comprises the following basic assembly:

color camera

Camera control unitConnection 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 operatedeither with multiwire or with coax/triax camera cable. The color camera head, thecamera control unit and remote control unit associated with the setup control consoleor remote control console are each equipped with a microcomputer.

The color camera uses a 3-tube RGB system with high grade beam splitter. Itis equipped with 1-inch plumbicon pickup tubes with dioxide gun system, bias lightand ABC facilities.

Various high grade lenses of different brands are available for camera. Thecamera control unit is of compact design. The connection between camera head andcamera control unit can be established either via a multiwire camera cable or via a

coax/triax camera cable.


28/32

28

DIMMER ROOM

Dimmer Room consists of light control system which give the variouslightening effects inthe 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 controlof intensity of some of the lamp, required for color matching.

* Using Electronic Dimmer, the operator is able to control the intensity of lampremotely. Theintensity of a group of the lamps can be adjusted individually or in oneof the two scenes.

*The system has been designed for large number of the loads, distributed on 415V,3phase,50Hz, 4 wire mains. The phase distribution both on the rack as well as on thelight 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 positionlever 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 5.0KW.

* 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 TVStudios, Theaters etc. this system is based on duplex communication system & has

4 stationsone master and three slaves.Special advantages of this:-


29/32

29

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).

Light Control:

The scene to be television must be well illuminated to produce a clear andnoise free picture. The lighting should also give the depth, the correct contrast andartistic display of various shades without multiple shadows.

The lighting arrangements in a TV studio have to be very elaborate. A largenumber of lights are used to meet the need of "key" "fell" and "back" lights etc. Lightsare classified as spot and soft lights. These are suspended from motorized hoists andtelescopes. The up and down movement is remote controlled. The switching ON andOFF 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 thestudios.

V. T .R. (Video tape recording):

It is the most complex piece of studio equipment with analog and digitalprocessor servo system, micro-processor, memory, logic circuits and mechanicaldevices etc.V.T.R

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

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 theV.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(offtelecast recording) is also recorded for the use in original news programme.

Specifications:

Video Cassette Recorders

Operational Environment

Operating temperature 5deg C to 40deg C.

Storage temperature -20deg C to 60 deg C.

Location to avoid :

*areas whose BVW-70P will be exposed to direct sunlight or any other stronglight.


30/32

30

* 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 Specifications

Power requirements AC 90 to 265V, 48 to 68 HzPower consumption 240WOperating temperature 5deg C to 40deg CStorage temperature -20deg C to 60deg C

Humidity Less than 80%

Weight 30 Kg.Dimensions 427*237*520 mm/w/h/oTape 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. Thisroom 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 engineerand a lighting engineer. The programme directors with the help of this staff effectsoverall 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 terminatedon separate panels in the control room. One panel contains the camera control unitand video mixer. In front of this panel are located a number of monitors for editingand previewing a incoming and outgoing programmes. Similarly another panelhouses microphone controls. This panel is under control of the sound engineer whois consultation with the programme director selects and controls the available soundoutput.

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.The producer can also talk over the intercom system to the VTR. The lighting iscontrolled by switches and faders from a dimmer console which in also located inthe control room.

PCR includes fol lowing two sections:


31/32

31

Vision MixerAudio distribution amplifier-ADA

ENG-CAMERA:

Eng means Electronic News Gathering. This camera is used for news coverage. It doesnot contain vacuum tube, rather contain charged couple device CCD. CCD is compactand 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 isused.

The camera has audio monitor.

The camera has video recorder which is also compact. The video tapeis of 30 minutes.

The camera make use of lens assembly for focusing purposes.

The different types of mikes used are as follows:Gun mikeLapel mikeRF mike

The gun mike has high gain. The lapel mike is used by news readers


32/32

12. Conclusion

In this sector of training I studied about the overall procedure and objective of the

Broadcasting process in elaborate form. All India Radio had provided us all the

equipments and apparatus for understanding us the each and every section up to its

depth. I visited the various sections like server and networking room, lines room,

control booth, captive earth station etc. After studying these sections I get

understood their execution and importance for the transmission and reception of the

data in All India radio.

Prasar Bharti is a public broadcaaster of India and is developing in terms of

technology and aspirations and truly public broadcaster

Documents

mohitReport Amity