doordarshan patna summer training

AMAL ROSHAN NIT CALICUT

2 0 1 3

SUBMITTED TO- SUBMITTED BY-

MD. YUSUF SIR AMAL ROSHANMD. YUSUF SIR AMAL ROSHANMD. YUSUF SIR AMAL ROSHANMD. YUSUF SIR AMAL ROSHAN

MAHESH LEPCHA SIR NIMAHESH LEPCHA SIR NIMAHESH LEPCHA SIR NIMAHESH LEPCHA SIR NIT CALICUTT CALICUTT CALICUTT CALICUT (2011(2011(2011(2011----15)15)15)15)

SERIAL NO SERIAL NO SERIAL NO SERIAL NO ---- 08080808



DECLARATION

I HEREBY DECLARE THAT WORK ENTITLED “SUMMER

TRAINING REPORT”, SUBMITTED TOWARDS COMPLETION

OF SUMMER TRAINING AFTER 2ND YEAR OF B.TECH

(ECE) AT NATIONAL INSTITUTE OF TECHNOLOGY (NIT)

CALICUT , COMPRISES OF MY ORIGINAL WORK PURSUED

UNDER THE GUIDANCE OF MR. MAHESH LEPCHA. THE

RESULTS EMBODIED IN THIS REPORT HAVE NOT BEEN

SUBMITTED TO ANY OTHER INSTITUTE OR UNIVERSITY

FOR ANY AWARD.

AMAL ROSHAN

B.TECH(2ND YEAR)



CERTIFICATE

THIS IS TO CERTIFY THAT MR. AMAL ROSHAN, A

STUDENT OF B.TECH, FROM NATIONAL INSTITUTE OF

TECHNOLOGY, CALICUT COMPLETED A 4 WEEK

VOCATIONAL SUMMER TRAINING PROGRAM AT

DOORDARSHAN PATNA, UNDER MY GUIDANCE AND

DIRECTION.

SIGNATURE OF THE GUIDE



ACKNOWLEDGEMENT

ON THE VERY OUTSET OF THIS REPORT, I WOULD LIKE TO EXTEND MY

SINCERE & HEARTFELT OBLIGATION TOWARDS ALL THE PERSONAGES

WHO HAVE HELPED ME IN THIS ENDEAVOR. WITHOUT THEIR ACTIVE

GUIDANCE, HELP, COOPERATION & ENCOURAGEMENT, I WOULD NOT

HAVE MADE HEADWAY IN THE PROJECT.

FIRST AND FOREMOST, I WOULD LIKE TO EXPRESS MY SINCERE

GRATITUDE TO MY PROJECT GUIDE, MR. MAHESH LEPCHA. I WAS

PRIVILEGED TO EXPERIENCE A SUSTAINED ENTHUSIASTIC AND

INVOLVED INTEREST FROM HIS SIDE. THIS FUELLED MY ENTHUSIASM.

I WOULD ALSO LIKE TO THANK MD. YUSUF SIR WHO ALWAYS GUIDED ME

IN RIGHT DIRECTION.

THIS WAS A TRULY AMAZING EXPERIENCE WHICH PROVIDED ME LIVE

EXPERIENCE OF AND WORKING METHODOLOGY OF VARIOUS EQUIPMENTS.

THANKING YOU.

AMAL ROSHAN



CONTENTS

• DOORDARSHAN HISTORY

• DOORDARSHAN PATNA

• FUNDAMENTALS OF MONOCHROME AND COLOUR TV

• COLOUR COMPOSITE VIDEO SIGNAL

• TV STUDIO

• TV CAMERA

• STUDIO LIGHTING

• MICROPHONE

• CABLES AND CONNECTORS

• PRINCIPLES OF VTR

• VISION MIXING

• TV TRANSMITTER

• EARTH STATION

• SATELLITE COMMUNICATION

• DTH



DOORDARSHAN HISTORY

Prasar Bharati is a statutory autonomous body established under the Prasar Bharati Act and

came into existence on 23.11.1997. It is the Public Service Broadcaster of the country. The

objectives of public service broadcasting are achieved in terms of Prasar Bharati Act through All

India Radio and Doordarshan, which earlier were working as media units under the Ministry

of I&B and since the above said date became constituents of Prasar Bharati

15 September, 1959 was the first day when the transmission of television

programme begin in India at a make shift studio in the All India Radio building. Pramita

Puri was the first announcer who started the programme with “shehnai recital' of Ustaad

Bismillah Khan. The programme was transmitted in a radius of 25 kilometers with a

small transmitter. From Black & White to becoming color in 1982 to digital telecast in

2004, the public broadcaster has grown with tune of time.

National telecasts were introduced in 1982. In the same year, color TV was introduced in the Indi

an market with the live telecast of the Independence Day speech by then prime minister Indira

Gandhi on 15 August 1982, followed by the 1982 Asian Games being held in Delhi. Now

more than 96 percent of the Indian population can receive Doordarshan (DD National)

programmes through a network of nearly 1400

terrestrial transmitters and about 46 Doordarshan studios produce TV

programs today.

SIGNIFICANT MILESTONES ACHIEVED WERE

• Launch of international channel -D India (14 March 1995)

• Formation of Prasar Bharti (Broadcasting Corporation of India) (23 November 1997)

• Launch of sports channels DD sports (18 March 1999)

• Launch of enrichment/ culture channel - DD Bharti (26 January 2002)

• Launch of 24 hours news channel - DD News (3 November 2002)

• Launch of free to air Direct – To – Home Service DD Direct+ (16 December 2004)

DTH –

DTH i.e. the direct to home telecast. This Service has been launched by DELHI

DOORDARSHAN from earth station KU Band Todapur, Delhi. It works on KU Band

width (11.7-13 GHz) This

service transponds perfectly up to 200 channels. Doordarshan’s DTH service is available

at National satellite, INSAT 4B.



DOORDARSHAN KENDRA:: PATNA AT A GLANCE

oordarshan Kendra, Patna was

inaugurated on the 13th October

1990 with an interim set up

converting a Government

Quarter located at Chhajubagh, Patna.

Adjacent area was demarcated for the

construction of a full-fledged studio.

The new studio building with all the

modern equipments and accessories

was finally inaugurated on the 15th

March 1996.

nitially, Doordarshan Kendra, Patna

started its programme having one

hour duration with the news

bulletin in Hindi for a duration of 15

minutes. A five-minute Urdu News

Bulletin was subsequently started in

May 1992 which was further increased

to 10 minutes in the year 1993. A

Satellite Link with all the Transmitters

of Bihar was established in 1994. The

commercial service at this Kendra was

introduced in the year 1995. The new

Studio Complex at Chhajubagh, Patna

started working in March 1999. The

Main Studio is having approximately

400 sq. meter areas. At present, this

Studio is being utilized for one shift

recording and one shift transmission.

ith the passage of time, the Kendra has been provided with the entire latest

technical infrastructure. At present, the infrastructure consists of full-fledged studio with state of art CCD Cameras and Digital Production Switcher. For ENG recording/ coverage, the Kendra is having Betacam and Digital DVCPRO Cameras. Two new 10 KW High Power Transmitter for DD-I and DD-II give primary service to an area around 75 kilometers radius. The Kendra has an uplink system, which caters to 3 HPT, 34 LPTs and 2 VLPTs (after bifurcation of the erstwhile State of Bihar) for relaying the regional service. One BEL Ob Van is available for OB Live telecast and recording. High Power TV Transmitter Complex is located at Bahadurpur, Patna.

D

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WAMAL ROSHAN NIT CALICUT


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STUDIO SET UP & COVERAGE DETAILS

� Studio - A (Main)

• Four Camera Digital set up

• For recording of programmes and other major activities.

� Studio - B (News)

• Two Camera digital set up

• For News & Regional transmissions

OB VAN

• Six Camera digital set up

• For outdoor major coverage such as Sports, Major functions etc. including live coverages.

� EFP VAN

• For outdoor coverage such as Crop seminar, Kalyani at village with 3 ENG (DVC) camera set up

� Earth Station

• Having two uplinking channels in digital mode. � ENG (Electronic News Gathering)

• With 12 portable ENG units for the purpose of day to day News and outdoor programmes coverage.

� Post production facilities

• Three nos. of Linear Edit Suits equipped with latest edit controllers.

• Two nos. of Non-Linear computer based edit suits.

• Computer based 3D Graphics facility.

• Separate studio for audio dubbing.

� Total coverage of Doordarshan in Bihar

• Doordarshan is covering both area & population wise 93.4% of the total population of 82.9 millions as per 2001 census.



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• TV coverage to uncovered areas is being provided through KU Band Free to AIR DTH Service of Doordarshan.

Doordarshan Network in Bihar

� Doordarshan Studio

• Patna (Major)

• Muzaffarpur (PGF)

� Doordarshan Transmitters (For Terrestrial Transmissions)

1. High Power Transmitters (HPTs) :

• Patna (10 KW)

• Muzaffarpur (1 KW)

• Katihar (10 KW)

� Low Power Transmitters (LPTs)

Name of LPTs/ VLPTs/DD News Under Doordarshan

Maintenance Centre

LOW POWER TRANSMITTERS

Gaya, Sasaram, Buxar, Jamui, Nawadah, Sheikhpura,

Aurangabad, Daudnagar and Bhabhua

Gaya

Bhagalpur, Munger, Begusarai, Khagaria, Lakhisarai,

Sikandara and Banka

Bhagalpur

Motihari, Siwan, Sitamarhi, Madhubani, Bettiah,

Gopalganj, Raxaul, Phulparas and Ramnagar

Motihari



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Darbhanga, Saharsa, Forbesganj, Madhepura,

Simaribakhtiarpur, Kishanganj, Rosra and Supaul

Purnia

VERY LOW POWER TRANSMITTERS

Masrakh and Marhaura

Motihari

DD News

High Power Transmitters at Patna (10 KW) and Muzaffarpur (1 KW)

LPT, Darbhanga – 500 watt, LPT, Gaya – 500 watt



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FUNDAMENTALS OF MONOCHROME AND

COLOUR TV SYSTEM

Picture formation A picture can be considered to contain a number of small elementary areas of light or shade

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 the pick up device

convert the optical image to a electric charge image depending on the light and shade of the

scene (picture elements). Now it is necessary to pick up this information and transmit it. For

this purpose scanning is employed. Electron beam scans the charge image and produces

optical image. The electron beam scans the image 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 the flicker reduces. The field rate is 50 Hertz. The frame rate is 25 Hertz.

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 channels in the R.F.

spectrum will be reduced. However, with more no. of TV lines on the screen the clarity of the

picture i.e. resolution improves. With lesser number of TV lines per frame the clarity

(quality) is poor.



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Resolution -The capability of the system to resolve maximum number of picture elements

along scanning lines determines the horizontal resolution. It means how many alternate black

and white elements can be there in a line. The vertical resolution depends on the number of

scanning lines and the resolution factor (also known as Kell factor)

Grey Scale- In black and white (monochrome) TV system all the colours appear as gray on a

10-step gray scale chart. TV white corresponds to a reflectance of 60% and TV black 3 %

giving rise to a Contrast Ratio of 20:1 (Film can handle more than 30:1 and eye's capability is

much more).

Brightness - Brightness reveals the average illumination of the reproduced image on the

TV screen. Brightness control in a TV set adjusts the voltage between grid and cathode of the

picture tube (Bias voltage).

Contrast-

Contrast is the relative difference between black and white parts of the reproduced picture. In

a TV set the contrast control adjusts the level of video signal fed to the picture tube.

Viewing Distance -Optimum viewing distance from TV set is about 4 to 8 times the height of

the TV screen. While viewing TV screen one has to ensure that no direct light falls on the TV

screen.

TELEVISION STANDARDS

• NTSC-National television standards committee(US) (525 Horizontal & 60 vertical lines)

• SECAM-System electronics for colour avec memorie(FRANCE)(625 vertical 50horizantal lines)

• PAL- Phase Alternating lines(GERMANY)(625 horizontal & 50 vertical line) Television standards used in India is PAL.



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Colour composite Video Signal(CCVS) • What is video signal?

Video is nothing but a sequence of picture. The image we see is maintained in our

eye for a 1/16 sec so if we see image at the rate more than 16 pictures per sec our

eye cannot recognize the difference and we see the continuous motion.

In TV cameras image is converted in electrical signal using photo sensitive material.

Whole image is divided into many micro particle known as Pixels.

These pixels are small enough so that our eyes cannot recognize pixel and we see

continuous image , thus at any instant there are almost an infinite no. of pixel that

needs to be converted in electrical signals simultaneously for transmitting picture

details. However this is not practicable because it is no feasible to provide a separate

path for each pixel in practice this problem is solved by scanning method in which

information is converted in one by one pixel line by line and frame by

frame.

Colour composite video signal is formed with video, sync and blanking signals. The

level is standardized to 1.0 V peak to peak (0.7 volts of video and 0.3 volts of sync

pulse). The Colour Composite Video Signal(CCVS) has been shown in the figure.

Frequency Content of TV Signal The TV signal have varying content. The lowest frequency is zero(when we are

transmitting a white window in the entire active period of 52 micro seconds the

frequency is Zero ). In CCIR system B the highest frequency that can be transmitted is

5 MHz even though the TV signal can contain much higher frequency components.

(In film the reproduction of frequencies is much higher than 5MHz and hence clarity

is superior to TV system.) long shots carry higher frequency components than mid

close ups and close ups. Hence in TV productions long shots are kept to a minimum.

In fact is a medium of close ups and mid close ups.



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DC Component of video signal and DC restoration A TV signal is a continuously varying amplitude signal as the picture elements give rise to

varying level which depends on how much of incident light the picture elements can reflect

and transmit the light signal to the TV camera. Hence the video signal has an average value

i.e. a DC component corresponding to the average brightness of the scene to scene.

RF Transmission of Vision and Sound Signals TV Transmission takes place in VHF Bands I and III and UHF Bands IV and V. Picture is

amplitude modulated and sound is frequency modulated on different carriers separated by

5.5 MHz. Also for video amplitude modulation negative modulation is employed because of

the following main advantages.

Pictures contain more information towards white than black and hence the average power

is lower resulting in energy saving. (Bright picture points correspond to a low carrier

amplitude and sync pulse to maximum carrier amplitude).

Interference such as car ignition interfering signals appear as black which is less

objectionable.

Picture information is in linear portion of modulation characteristic and hence does not

suffer compression. Any compression that may take place is confined to sync pulse only.

The design of AGC circuit for TV Receiver is simpler. AM produces double side bands. The

information is the same in both side bands. It is enough to transmit single side band only.

Carrier also need not be transmitted in full and a pilot carrier can help. However,

suppressing the carrier and one complete side band and transmitting a pilot carrier leads to

costly TV sets. A compromise to save RF channel capacity is to resort to vestigial side band

system in which one side band in full, carrier and a part of other side band are transmitted.

Sound Signal Transmission

In CCIR system B sound carrier is 5.5 MHz above the vision carrier and is

frequency modulated. The maximum frequency deviation is 50 KHz. Also the ratio of

vision and sound carriers is 10:1 (20:1 is also employed in some countries) If we assume

maximum audio signal is 15 KHz the band width is 130 KHz. According to Carson's Rule the

bandwidth is 2 x (Maximum frequency deviation + highest modulating frequency).

However, calculated value(using Bessel's function) of Bandwidth is 150 KHz i.e. 75 KHz on

either side of sound carrier. In CCIR system picture IF is 38.9 MHz and sound.

IF is 33.4 MHz. At the receiver end it is necessary to ensure that signal frequencies in



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the region of the vestigial side band do not appear with double amplitude after

detection. For this purpose the IF curve employs NYQUIIST slope.

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. The retina of human eye consists of very large number of

light- sensitive cells. These are of two types, rods and cones. Rods are sensitive only to the

intensity of the incident light and cones are responsible for normal colour vision. The small

range of frequencies to which the human eye is responsive is known as visible spectrum.

This visible spectrum is from 780 mm (Red) to 380 mm(Violet).

Additive Colour Mixing The figure shows the effect of projecting red, green, blue beams of light so that they overlap

on screen. Y= 0.3 Red + 0.59 Green + 0.11 Blue

Additive colour mixing



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TV STUDIO

A TV studio is an acoustically treated compact anechoic room. It is suitably furnished and

equipped with flood lights for proper light effects. The use of dimmer stats 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 the programme.

In addition to a live studio, video tape recording and telecine machine rooms are located close

to the control room. In most cases, programmes as enacted in the studio are recorded on a

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

output passing through the same control room.

TV STUDIO CONSTITUENTS-

• POWER SUPPLY

• ACOUSTICS

• CAMERA

• AUDIO SYSTEM (MICROPHONE AND AUDIO CONSOLE)

• LIGHTS

• AIR CONDITIONING

• SPEAKERS

• COMMUNICATION SYSTEMS

• POST PRODUCTION AND VIDEO EFFECTS

• MSR

• VTR Patna Doordarshan has 2 dedicated 11kV ac sources. Its power supply is divided into two

parts - (i) Essential (ii) Non Essential power supply. 4 generators (45kv, 45kV, 40kV, 20kV)

are also available for emergency backup. 4 UPS are also available for the same purpose.



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ACTION AREA OF TV STUDIO-



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TV CAMERA

KEY TERMS The camera utilizes two devices that control the amount of light that will reach the sensor.

• One of these devices is the shutter that can be likened to a normally closed opaque

window shade. When activated the window shade will be opened for a predetermined period

of time to admit light to the sensor.

• The other device is the aperture control that is an iris diaphragm located inside the lens

and the diaphragm functions much like the iris in the human eye. This diaphragm is made

either larger or smaller in size to control the amount of light passing through the lens to the

sensor.

• Shutter Speed

• The shutter speed of the camera specifies how fast the shutter will operate that is for how

long a period of time the shutter will be open to admit light through the lens. A faster shutter

speed will be better to stop motion. A slower shutter speed can permit use of a smaller

aperture that will result in a greater depth of field (to be explained in a few minutes). Shutter

speeds are expressed in numbers such as 60, 125, 250 etc. The number 60 means 1/60 of a

second and 125 means 1/125 of a second and so on. A special setting is sometimes included

and labeled B. When B is used the shutter will remain open as long as the shutter release

remains pressed. The B stands for Bulb an expression that goes back to operation of old

cameras. Each time you increase the speed you reduce the light striking the film. As the

shutter speed goes from 60 to 125 you cut the light in half. You do exactly the same if you go

from 250 to 500. Full stop shutter speeds are; 1, ½ , ¼, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250,

1/500, 1/1000, 1/2000, 1/4000, 1/8000.



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Aperture

• The aperture controls the amount of light that passes through the lens to the sensor. On a

cloudy day you need to make the diaphragm opening larger to allow more light to reach the

film and conversely on a bright day at the beach you need to close down the diaphragm to let

less light in. The numbers used to identify the discrete steps are 1.4, 2, 2.8, 4, 5.6 8, 11, 16,

22, etc. and are known as f-stops. I know the numbers are strange looking but they have a

basis in mathematics and as the number increases by one stop the light getting through the

lens is cut in half. Thus if you go from f2 to f2.8 you cut the light in half. You also cut it in

half if you go from f11 to f16. Just to reinforce the idea if you go from f16 to f11 you double

the light reaching the lens. The term “stopping down” refers to closing down the diaphragm

such as going from f11 to f16. Notice as the f-stop numbers get larger the diaphragm gets

smaller.

Lens Selection

• Lens selection has a great affect on your images. Lenses are measured in terms of focal length.

Telephoto lenses have a long focal length and wide- angle lenses have a short focal length. For

35mm a 50mm lens is called a “normal” lens since that lens sees approximately the same field of

view that the human eye and brain see when they look at a scene. Let us look at lenses from the

following perspective. Say that you are standing at one point and attempting to photograph a

subject of a given size with a 50mm lens. If the object that you want to photograph appears too

small in the viewfinder a longer telephoto lens will allow you to fill more of the frame with that

subject without moving closer.

Zoom Lens

A zoom lens has a variable focal length with a range of 10 : 1 or more. In this lens the viewing angle

and field view can be varied without loss of focus. This enables dramatic close-up control. The

smooth and gradual change of focal length by the cameraman while televising a scene appears to

the viewer as it he is approaching or receding from the scene.

The variable focal length is obtained by moving individual lens elements of a compound lens

assembly. A zoom lens can in principle simulate any fixed lens which has a focal length within the

zoom range. It may, however, be noted that the zoom lens is not a fast lens. The speed of a lens is

determined by the amount of light it allows to pass through it. Thus under poor lighting conditions,

faster fixed focal length lenses mounted on the turret are preferred.



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A TYPICAL STUDIO CAMERA

A typical view of cameras used in studios.

In the above figure TV camera and its various

components are shown.

In the right side figure TV camera on a studio

pedestal.



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A TV Camera consists of three sections.

a) A Camera lens & 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 a electrical signal

c) Electronics: To process output of a transducer to get a CCVS signal

Types of Pickup Devices- a) Photo emissive material: These material emits electrons when the light falls on them. Amount of

emitted electrons depends on the light . Monochrome cameras used in Doordarshan were based on

this material. These cameras were called Image Orticon Cameras. These cameras were bulky and

needed lot of light. These are no longer in use at present.

b) Photo conductive material: The conductivity of these material changes with amount of light falling

on them. Such material with variable conductivity is made part of a electrical circuit. Voltage

developed across this material is thus recovered as electrical signal. Earlier cameras based on this

principle were Videocon Cameras. Such cameras were often used in the monochrome televise chain.

These cameras had serious Lag & other problems relating to dark currents.

Improvement in these cameras lead to the development of Plumb icon and Sat icon cameras.

c) Charge coupled devices: These are semiconductor devices which convert light into a charge image

which is then collected at a high speed to form a signal. Most of the TV Studios are now using CCD

cameras instead of Tube cameras. Tube cameras have become obsolete & are not in use .



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Camera sensors – CCD basics

The CCD is a solid-state device using special integrated circuitry technology, hence it is often referred

to as a chip camera. The complete CCD sensor or chip has at least 450 000 picture elements or

pixels, each pixel being basically an isolated (insulated) photodiode. The action of the light on each

pixel is to cause electrons to be released which are held by the action of a positive voltage.

The Charge held under electrode can be moved to electrode by changing the potential on the second

electrodes. The electrons (negative charges) follow the most positive attraction. A repeat of this

process would move the charges to next electrode, hence charge-coupled device. A system of

transfer clock pulses is used to move the charges in CCDs to achieve scanning.

There are three types of CCD device: frame transfer (FT)

interline transfer(IT)

frame interline transfer (FIT)

Frame transfer (FT)

Frame transfer was the first of the CCDs to be developed and it consists of two identical areas, an

imaging area and a storage area. The imaging area is the image plane for the focused optical image,

the storage area is masked from any light. The electrical charge image is built up during one field

period, and during field blanking this charge is moved rapidly into the storage area. A mechanical

shutter is used during field blanking to avoid contamination of the electrical charges during their

transfer to the storage area. The storage area is „emptied' line by line into a read- out register

where, during line –time, one line of pixel information is „clocked' through the register to produce

the video signal.

Interline transfer (IT)

Interline transfer CCDs were developed to avoid the need for a mechanical shutter The storage cell is

placed adjacent to the pick-up pixel; during field blanking the charge generated by the pixel is shifted

sideways into the storage cell. The read-out process is similar to the frame transfer device, with the

storage elements being „clocked' through the vertical shift register at field rate into the horizontal

shift register, then the charges read out at line rate. Earlier forms of IT devices suffered from severe

vertical smear, which produced a vertical line running through a highlight. This was caused by

excessive highlights penetrating deeply into the semiconductor material, leaking directly into the

vertical shift register. Later IT devices have improved the technology to make this a much less

objectionable effect.

Frame interline transfer (FIT)

Frame interline transfer CCDs are a further development of the interline transfer device to overcome

the problem of vertical smear. As its name suggests, it is a combination of both types . The FIT

sensor has a short-term storage element adjacent to each pixel (as IT) and a duplicated storage area



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(as FT). During field blanking the charges are moved from the pixels into the adjacent short-term

storage element and then moved at 60 times field frequency into the storage area. This rapid

moving of the charge away from the vulnerable imaging area overcomes the vertical smear problem.

Development in CCD technology has seen the introduction of:

• The hole accumulated Diode (HAD) sensor which enabled up to 750 pixels/line, with

increased sensitivity and a reduction in vertical smear;

• The hyper HAD sensor, which included a microlens on each pixel to collect the light more

efficiently (this gave a one stop increase in sensitivity over the HAD sensor);

• The power HAD sensor with improved signal-to- noise ratio which has resulted in at least

half an ƒ-stop gain in sensitivity; in some cases a full ƒ-stop of extra sensitivity has been

realized.

CCD CAMERAS (Charge coupled devices)—

A typical three tube camera chain is described in the block diagram. The built in sync pulse generator

provides all the pulses required for the encoder and colour bar generator of the camera. The signal

system is described below:

The signal system in most of the cameras consists of processing of the signal from red, blue and

green CCD respectively. The processing of red and blue channel is exactly similar. Green channel

which also called a reference channel has slightly different electronic concerning aperture

correction. So if we understand a particular channel, the other channels can be followed easily. So

let us trace a particular channel. The signal picked up from the respective CCD is amplified in a stage

called pre-pre amplifier. It is then passed to a pre amplifier board with a provision to inserts external

test signal. Most of the cameras also provide gain setting of 6 dB, 9dB and 18dB at the pre amplifier.

Shading compensator provides H and V shading adjustments in static mode and dynamic mode by

readjusting the gain. After this correction the signal is passed through a variable gain amplifier which

provides adjustment for auto white balance, black balance and aperture correction. Gama correction

amplifier provides suitable gain to maintain a gamma of 0.45 for each channel. Further signal



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processing includes mixing of blanking level, black clip, white clip and adjustment for flare

correction. The same processing take place for blue and red channels. Green channel as an

additional electronic which provides aperture correction to red and blue channels. Aperture

correction provide corrections to improve the resolution or high frequency lost because of the finite

size of the electron beam . Green channel has fixed gain amplifier instead of variable gain amplifier

in the red and blue channels.

All the three signals namely R, G and B are then fed to the encoder section of the camera via a

colour bar/camera switch. This switch can select R, G and B from the camera or from the R, G, B

Signal from colour bar generator. In the encoder section these R, G, B signals are modulated with SC

to get V and U signals. These signals are then mixed with luminance, sync, burst, & blanking etc. to

provide colour composite video signal (CCVS Signal). Power supply board provides regulated voltages

to various sections.

Other Types Of Cameras-

• ENG/EFP CAMERAS AND CAMCORDERS-

(ELECTRONIC NEWS GATHERING/ELECTRONIC FIELD PRODUCTION)

These have in built recording

system. Major advantage is

that they are mobile.

• Consumer Cameras



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• Proconsumer Cameras



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STUDIO LIGHTINGSTUDIO LIGHTINGSTUDIO LIGHTINGSTUDIO LIGHTING

GENERAL PRINCIPLES:

Lighting for television is very exciting and needs creative talent. There is always a

tremendous 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., wavelength from

700 nm to 380 nm respectively. However to effectively use the hardware and software

connected with lighting it is important to know more about this energy.

The lighting control system is the most important tool that the lighting man has to work

with. The lighting control system, commonly called the Dimming System, is the nerve centre

of any lighting package. The Control System allows the studio production lights to be varied

in intensity for the various special effects that are required. It’s dimming system that allows

color blending of the cyclorama curtain background. It is the dimming system that allows

complex light changes to be easily accomplished.

Lighting in studio is of three types-

• Key Light-

It is used to illuminate the main object. It has most intensity.

• Fill Light-

It is used to remove blank shadows and the shadows created by key light.

• Back Light-

It is used to give the object a 3D look. It helps to give a depth in the video.

Other lightings are background lights and lights synchronized with audio.

Light Source: Any light source has a Luminance intensity (I) which is measured in

Candelas. One Candela is equivalent to an intensity released by standard one candle source

of light.

Luminance flux (F): It is a radiant energy weighted by the photonic curve and is

measured in Lumens. One Lumen is the luminous flux emitted by a point source of 1

Candela.

Illumination (E): It is a Luminous Flux incident onto a surface. It is measured in

LUMENS/m2, which is also called as LUX. A point source of 1 candela at a uniform

distance of 1 meter from a surface of 1 square meter gives illumination of 1 LUX.

Luminance (L): It is a measure of the reflected light from a surface. Measured in

Apostilbs . A surface which reflects a total flux of 1 lumen/m2 has a luminance of 1



29 | P a g e

Aposilbs .

Elementary theory of light also says that:

Colour temperature:

One may wonder, how the light is associated with color . Consider a black body being

heated; you may observe the change in colour radiated by this body as the temperature

is increased. The colour radiated by this body changes from reddish to blue and then to

white as the temperature is further increased. This is how the concept of relating colour

with temperature became popular. Colour temperature is measured in degree Kelvin

i.e., 0C +273) . The table below gives idea about the kind of radiation from different

kinds of lamps in terms of colour temperature.

a) Standard candle 19300K

b) Fluorescent Lamps range 3000-6500oK

c) HMI lamp 5600+- 400oK

(H=Hg, M=Medium arc, I=Metal Iodide}

d) CSI (Compact Source Iodide) 4000+- 400oK

e) CID (Compact Iodide Daylight) 5500+- 400o

Colour TV Display,white 6500oK

f) Monochrome TV 9300oK

g) Blue sky 12000 – 18000oK

h) Tungsten Halogen 3200oK

i) Average summer sunlight (10am –3pm) 5500oK

It can be noted that as the temperature is increased, the following things

happen:

1) Increase in maximum energy released

2) Shift in peak radiation to shorter wavelengths (Blue)

3) Colour of radiation is a function of temperature

Hence by measuring the energy content of the source over narrow bands at the red and

blue ends of the spectrum ,the approximate colour temperature can be determined. All the

color temperature meter are based on this principle.



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COLOUR FILTERS AND THEIR USE:

Colour filters are used to modify the colour temperature of lights and to match colour

temperature for cameras while shooting with different colour temperature. These filters

change the colour temperature at the cost of reduction in light transmission. Colour

temperature filters are also introduced in the optical path of cameras to facilitate camera

electronics to do the white balance without loading the amplifier chain. Cameras electronics

is generally optimized for a colour temperature of 3200K, hence it uses reddish filter while

shooting at higher colour temperatures.

Generally it is normal to correct daylight to produce tungsten quality light, because it is

usually easier to do and saves lot of power, otherwise blue filters are going to reduce lot of

light thus requiring the use of higher wattage lamps.. However, when the amount of

tungsten to be corrected is small it may be more practical to convert it to daylight, but with

a considerably reduced light output form the luminaries. There are two basic types of filter:-

i) One which is orange in colour and converts Daylight to Tungsten Light.

ii) One which is blue in colour and converts Tungsten to Daylight.

Day Light: -

The sun does not changes its colour temperature during the day it is only its appearance

from a fixed point on earth. It is because the sunlight gets scattered because of the medium,

shorter wavelengths like blue gets more effected. Certain situations like, sunrise and sunset

causes the light to be more yellow than midday, because the light has to travel the long

distance so a careful note should be made of the Transmission factor of each of the filters.

Often a compromise has to be reached in terms of correction and light loss.

NEUTRAL DENSITY FILTERS :-

In addition to colour temperature correction sometimes it may be necessary to reduce the

intensity of daylight at an interior location. Neutral density filters available to attenuate the

light are of:

0.3 Density which has a transmission of 50%= 6dB=1 f stop

0.6 Density which has a transmission of 25%= 9dB=2 f stop

0.9 Density which has a transmission of 13%= 12dB=3f stop

COMBINATION OF CTC FILTERS AND NEUTRAL DENSITY

FILTERS:

Single filters exist which are a combination of full colour temperature orange and neutral

density as follows:-

Full Orange + 0.3 N.D. with a transmission of 50%

Full Orange + 0.6 N.D. with a transmission of 38%

The HMI light source has a colour temperature of about 60000K and can be used with

exterior daylight without the need for a colour temperature correction filter.



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DIFFERENT LIGHTING TECHNIQUES:

- Eye light, Low intensity light on camera itself to get extra sparkle to an actor's eye

-Rim light, to highlight actor's outline, it is an extra back on entire body at camera level

- Kickkar light, Extra light on shadow side of the face at an angle behind and to the side of

the actor

- Limbo Lighting, Only subject is visible, no back ground light

- Sillhoutt lighting, No light on subject, BG is highly lit

LIGHTING CONSOLE

In a television production, each scene will require its own lighting plan to give the desired

effect. In order to assist in setting up a particular lighting plon, a console should provide :-

a) One man operation and a centralised control desk with ability to switch any circuit.

b) Facilities to obtain good balance with flexibility to have dimming on any circuit.

c) With all controls for power at low voltage and current.

Modern lighting consoles also provide file & memory to enable the console operator to

store and recall the appropriate luminaries used for a particular lighting plot. These console

also provide Mimic panels to show which channels are in use and which memories or files

have been recalled.

DIMMERS

Three basic methods for dimming are :-

1. Resistance

This is the simplest and cheapest form of dimmer. It consists of a wire wound resistor with a

wiper .It is used in series with the load.

2. Saturable Reactor (System SR)

The basic principle of the saturable reactor is to connect an iron cored choke in series with

the lamp. Dimmers are controlled with the help of main switch. A typical dimmer bank is

shown.

LIGHTING THE SET FOR DRAMA:--

Openings such as windows within a set should be

highlighted without overstating them. Where the

walls having such feature should be lit to reveal

these features but care must be taken to ensure

that there is only one shadow. The top of the set

should be darkened off by using the barndoors,

this puts a "ceiling" on the set by giving the

feeling of a roof. If more than the top of the set

is darkened, that gives enclosed feeling.



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Indoor day time:

1. If there is a choice in the direction of the 'sun'(Key) take the shortest route inside the set

to a wall, and if possible throw the shadow of window bars onto a door - it usually is in shot.

2. A patch of light on the floor inside the set, backlight from outside using a soft source at

steep elevation adds realism.

3. When a set does not have a window, a window pattern can be projected onto a wall to

produce a suitable window effect.

4. Roof and Ceiling Pieces - if they make lighting impossible, check if they can be removed at

the planning state. Light any ceiling pieces from outside, use a soft source at ground level. If

the ceiling has plaster moulding or ornamentation, a hard source may be used.

Indoor night time:

- The outside of the window should be dark, except for a possible dim skyline if the room is

well above adjacent streets, or lit by an outside practical lamp i.e. street lighting.

- The wall with the window in it should be lit at night to be brighter than for the day

condition. Subjectively the walls appear brighter at night than at daytime.

- Often a completely different 'feel' to the set can be obtained by reversing he direction of

lighting in the set compared to that used for day.

- General for night effects it is not a good plan to just simply dim the set lighting when

changing from day to night. This is because the excessive change in colour temperature of

the light source and the apparent increase in saturation of surfaces at low luminance.

Outdoor daylight and Moonlight:

The direction of the light is dictated by the position of the 'sun' or 'moon'. As a general

principle one should remember that sunlight (hard source) is accompanied by the reflected

"skylight" (soft source) whereas moonlight is a single hard source. One of the biggest

problems when lighting exteriors is the maintenance of “single shadow" philosophy - double

shadows on a long shot will quickly destroy the apparent realism created in the set. Very

large area filler light is ideal for exterior daylight scenes.

This can be achieved by using a suspended white screen 12' x 8' where the filler would be

positioned then lighting it with hard light.

The exact lighting treatment will depend on the situation but as a general rule, moonlight

effects are normally achieved by back lighting to give a more softer, romantic mood than

would be achieved than a frontal key.

In colour, to obtain a night effect, blue cinemoid is used over the luminaries. This gives a

stylised effect. An alternative is to use much more localised lighting than for daylight and

light only the artists and odd parts of the set.



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Various other lighting equipments-

Frensel Spotlight Cylorama Lights

Scoop Lights Pantograph



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Dynabeam Lights Wide Anlge Lights

Lightbeam with Patterns

Space Cycle lights



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MICROPHONES

Introduction Pressure variations, whether in air, water or other mediums, which the human ear can detect,

are considered sounds. Acoustics is the science or the study of sound. Sound can be generally

pleasing to the ear, as in music, or undesirable, referred to as noise. The typical audible range

of a healthy human ear is 20 to 20,000 Hz. A Sound Pressure Level

(SPL) beyond the detectable frequencies of the human ear can also be very important to

design engineers. Noise, Vibration and Harshness (NVH) is concerned with the study of

vibration and audible sounds. Vibrations represent a rapid linear motion of a particle or of an

elastic solid about an equilibrium position, or fluctuation of pressure level.

Harshness refers to the treatments of transient frequencies or shock. Usually

treatments are employed to eliminate noise, but in some cases products are designed to

magnify the sound and vibration at particular frequencies. The sound

produced or received by a typical object, which may be above and below the frequencies that

are detectable by the human ear, or amplitudes concerning its resonant

frequencies, are important to designers, in order to characterize the items performance and

longevity.

Technology Fundamentals and Microphone Types

When an object vibrates in the presence of air, the air molecules at the surface will begin to

vibrate, which in turn vibrates the adjacent molecules next to them. This

vibration will travel through the air as oscillating pressure at frequencies and amplitudes

determined by the original sound source. The human eardrum transfers these

pressure oscillations, or sound, into electrical signals that are interpreted by our brains

as music, speech, noise, etc. Microphones are designed, like the human ear, to transform

pressure oscillations into electrical signals, which can be recorded and analyzed to tell us

information about the original source of vibration or the nature of the path the sound took

from the source to the microphone. This is exhibited in testing of noise reducing materials.

Pressure from sound must be analyzed in the design stages to not only protect the



36 | P a g e

materials around it, but also to protect the most precious and delicate

mechanism designed to perceive it, the human ear. Like the human ear,

microphones are designed to measure a very large range of amplitudes, typically measured

in decibels (dB) and frequencies in hertz (Hz.)

In order to convert acoustical energy into electrical energy, microphones are used. There are a

few different designs for microphones. The more common designs are Carbon

Microphones, Externally Polarized Condenser Microphones, Prepolarized Electret

Condenser Microphones, Magnetic Microphones, and Piezoelectric Microphones.

Types of microphone Connectors-

• BALANCED

In general, microphones provide an analogue audio

signal. Professional microphones feature an

XLR-output with three pins that transfer a balanced

signal. One pin is ground, and the other two carry the audio

signal. Pin 2 is the so called hot signal and pin 3 the

cold. This method reduces the susceptibility of external

noise while allowing the usage of longer cables.

• UNBALANCED

Entry level microphones often feature an attached cable with

an unbalanced 6.3 mm or 3.5 mm connector. An unbalanced

output carries the signal on a single conductor and is more

susceptible to external noise. For that reason only balanced

connections are used in professional miking applications.

• USB

More and more professional USB microphones are available. A

USB microphone is essentially a mic with a built-in USB audio

interface that converts the analogue signal into a digital signal. It

can be directly plugged into a computer without requiring an exter-

nal audio interface.

USB microphones, such as the Shure PG27USB and the

PG42USB with plug and play functionality are an easy start into

home recording and podcasting.



37 | P a g e

Types of Microphones

• Dynamic

Dynamic microphones employ a diaphragm, a voice coil and a magnet. The voice

coil is sur-rounded by a magnetic field and is attached to the rear of the diaphragm. The

motion of the voice coil in this magnetic field field generates the electrical signals corresponding to

the picked up sound. Dynamic microphones have a relatively simple construction and are

therefore economical and rugged. They can handle extremely high sound pressure levels

and are largely unaffected by extreme temperatures or humidity.

• Condenser

Condenser microphones are based on an electrically-

charged diaphragm/ backplate assembly which forms a

soundsensitive capacitor. When the diaphragm is set in motion

through sound, the space between the diaphragm and the

backplate is changing, and therefore the capacity of the

capacitor. This variation in spacing produces the electrical signal.

Condensers are more sensitive and can provide a smoother, more

natural sound, particularly at higher frequencies. All condenser microphones need to be powered:

either by batteries in the microphone,by phantom power provided by a mixer, a sound card or an

external analogue to digital converter

There are two main types of condenser microphones:

Small diaphragm – generally used for live performance and recording. They are called

small diaphragm because the transducer’s diaphragm is less than one inch in diameter.

Small diaphragm microphones provide a more natural sound reproduction and are

preferably used for miking instruments.

Large diaphragm – traditionally favored by recording studio engineers and broadcast

announcers, condenser microphones with a large diaphragm (one inch in diameter or

larger) usually have higher output, less self-noise (the “hiss“ the microphone might

make), and better low-frequency response, which can result in a “higher fidelity“

sound for both vocals and instruments.



38 | P a g e

BASED ON PICKUP PATTERN(POLAR DIAGRAM)

• OMNIDIRECTIONAL

An omnidirectional microphone picks up

sounds equally from all directions and

reproduces the sound source more natural

than a unidirectional microphone. It is

good for natural room sound and group

vocals. Also good for when the singer or

talker may move around different sides of

the microphone (but their distance to the

mic stays the same).

As an omnidirectional microphone picks up all

the ambient sound in a room, e.g. the

computer fan, it is not the recommended choice for home recording. However, if the

goal is to enable listeners to hear what is occurring in the background, you should

consider an omnidirectional pick-up pattern.

• CARDIOID

This is the most common type of microphone.

It is called “cardioid“ due to its

heart-shaped pick up pattern and has the

most sensitivity at the front and is least sensitive

at the back. This microphone helps

reduce pickup of background noise or

bleed from nearby sound sources.

• SUPERCARDIOID

A supercardioid microphone is even more directional

than the cardioid. Supercardioids

have the tightest pickup pattern, further isolating

the sound source. But they also have some

pickup at the rear. Good for noisy, crowded spaces

and when multiple microphones arebeing used, such

as for round-table discussions where you want to

keep the voices distinct



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ON THE BASIS OF FREQUENCY RESPONSE-

• FLAT FREQUENCY RESPONSE

All audible frequencies (20 Hz – 20 kHz) have

the same output level. This is most

suitable for applications where the sound

source has to be reproduced without

changing or “coloring” the original sound.

• TAILORED FREQUENCY RESPONSE

A tailored response has varying output levels

across the frequency range and is usually

designed to enhance a sound source in a

particular application. For instance, a bass

drum microphone does not need to reproduce

high frequencies above 6 kHz or a vocal

microphone may have a peak in the 2 – 4 kHz

range to increase intelligibility

MIicrophone in a recording

studio



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CABLES AND CONNECTORS

• The earliest use of cables was in Telegraphy lines. The cables were termed as SWER (Single

Wire Earth Return) circuits. These are single phase lines (un-insulated), that were used in

Single Wire Transmission. The use of this form of communication soon started having

interference (noise) from the Trams (Electric Trains) and other electricity-using devices.

• After this, companies converted to Balanced circuits lines. These are implemented using two

wires which have circuits installed at every distance, or at the receiving or transmitting end,

that cancel out the interference.

– Secondly, since the they are two wires, on transmitting and the other receiving, the

interference in the two lines is canceled out automatically.

– Balanced lines increase length by decreasing the signal attenuation.

• Since most of the telephone lines were installed next to power lines, this caused the

interference that is induced from the power lines, and with the advancement of power, the

interference kept on increasing.

• This brought in a new era of the wire transposition, Figure 4 in a bid to reduce on the

interference induced into the cables. In wire transposition, the transmit and receive cables

change position every 6 to 7 poles (around 4 twists every Kilometer). The change in position

helps to increase interference cancelation.

The wire transposition was not enough in the reduction of noise in the communication lines. This led

to the introduction of twisted pair cables.

Types of Cables-

1. E1

2. Ethernet

3. Coaxial

4. Fiber

5. Waveguide

6. Wireless Medium

E1/T1-

Depending on the Size of the Cable, it can carry from 8 to 32 E1s/T1s, each E1 being made up of

4 twisted cables. Each pair of cables is twisted onto each other to achieve noise cancellation.

Please note that E1s can also be achieved using the an RJ 45 Connector.

Coaxial-Coaxial cables provide the simplest and most versatile method for transmission of RF

and microwave energy. The common types consist of a cylindrical metallic inner conductor

surrounded by a dielectric material and then enclosed by a cylindrical metallic outer conductor.



41 | P a g e

The dielectric material is used to maintain the inner conductor concentrically within the outer

conductor. The dielectric material is typically polyethylene (PE), Polyproplene (PP) or

tetraflouroethylene (TFE). Most coaxial cables are then coated with a protective jacket made of

polyethylene or poly-vinyl chloride (PVC).

Fiber-

An optical fiber or optical fiber is a thin, flexible, transparent fiber that acts as a waveguide, or

"light pipe", to transmit light between the two ends of the fiber. Optical fibers are widely used in

fiber-optic communications, which permits transmission over longer distances and at higher

bandwidths (data rates) than other forms of communication. Fibers are used instead of metal

wires because signals travel along them with less loss and are also immune to electromagnetic

interference. Fibers are also used for illumination, and are wrapped in bundles so they can be

used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for

a variety of other applications, including sensors and fiber lasers.

Optical fiber typically consists of a transparent core surrounded by a transparent cladding

material with a lower index of refraction. Light is kept in the core by total internal reflection. This

causes the fiber to act as a waveguide.

Two types of Fiber media :

Multimode

Singlemode

Single-mode fiber

Carries light pulses along single path

Uses Laser Light Source

Has a very small core and carry only one beam of light. It can support Gbps data

rates over > 100 Km without using repeaters.

Multimode fiber

Many pulses of light generated by LED travel at different angles

Can support less bandwidth than Single mode Fiber



42 | P a g e

Waveguides-

In electromagnetics and communications engineering, the term waveguide may refer to any

linear structure that conveys electromagnetic waves between its endpoints. However, the

original and most common meaning is a hollow metal pipe used to carry radio waves. This type

of waveguide is used as a transmission line mostly at microwave frequencies, for such purposes

as connecting microwave transmitters and receivers to their antennas, in equipment such as

microwave ovens, radar sets, satellite communications, and microwave radio links.

A dielectric waveguide employs a solid dielectric rod rather than a hollow pipe. An optical fiber is

a dielectric guide designed to work at optical frequencies. Transmission lines such as microstrip,

coplanar waveguide, stripline or coaxial may also be considered to be waveguides.

The electromagnetic waves in (metal-pipe) waveguide may be imagined as travelling down the

guide in a zig-zag path, being repeatedly reflected between opposite walls of the guide. For the

particular case of rectangular waveguide, it is possible to base an exact analysis on this view.

Propagation in dielectric waveguide may be viewed in the same way, with the waves confined to

the dielectric by total internal reflection at its surface. Some structures, such as Non-radiative

dielectric waveguide and the Goubau line, use both metal walls and dielectric surfaces to confine

the wave.

Types of waveguides:

- Rectangular waveguide: This is the most commonly used form of waveguide and has a

rectangular cross section.

- Circular waveguide: Circular waveguide is less common than rectangular waveguide. They have

many similarities in their basic approach, although signals often use a different mode of

propagation.

- Circuit board stripline: This form of waveguide is used on printed circuit boards as a

transmission line for microwave signals. It typically consists of a line of a given thickness above

an earth plane. Its thickness defines the impedance.

Uses:

- Optical fibers applications

- In microwave, a waveguide guides microwaves from a magnetron were waves are formed.

- In radar applications

Stripline – Waveguides for printed circuit boards

Waveguides



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Important parameters of cables-

1. Characteristic Impedance

2. VSWR (Voltage Standing Wave Ratio)

3. Capacitance

4. Power Rating

5. Maximum Operating Voltage

6. Attenuation

7. Electrical length stability

8. Pulse Response

9. Shielding

10. Cut Off frequency

11. Flexibility

12. Cable design and Construction

13. Operating temperature range

14. Cable noise

Various Types of Connectors Used Are-

� BNC connectors (Bayanet Neill Concelnam/ Bayanet Navy Connector)

� SMA connectors (Subminiature A)

� SMC connectors (Subminiature C)

� TNC connectors (Threshold Navy Connectors)

� RCA connector (Radio Connector of America)

� Elbow connectors



44 | P a g e

PRINCIPLES OF VIDEO TAPE

RECORDING

Introduction

Video tape recorder is a most complex piece of studio equipment with analog and digital processing

servo system, microprocessors, memories, logic circuits and mechanical devices etc. Also these

recorders have been the main limitation so for as the quality output from studio is concerned. Right

from fifties, continuous efforts are being made to improve its performance so as to reproduce

cameras faithfully by improving S/N ratio and resolution. Designer for video tape recorders had to

consider the following differences in the video and audio signals:

Magnetic Principle

Magnetic field intensity H = NI / L

Magnetic flux density B = H

Magnetic Flux Ø= BA

( is of the order of 100 to few 10,000 for ferromagnetic materials) Property of the ferromagnetic

materials to retain magnetism even after the current or the H is removed is called retentivity and is

used for recording electrical signals in magnetic form on magnetic tapes. This relationship can also

be represented by a curve called BH curve. Magnetic tapes are made of ferromagnetic materials

with broader BH curve than the material used for video heads as the heads are not required to

retain information.



45 | P a g e

WRITING SPEED AND FREQUENCY RESPONSE

Recording Process

With reference to given figure when a tape is passed over the magnetic flux bubble,

the electric signal in the coil will cause the electric lines of force from the head gap to

pass through the magnetic material of the tape producing small magnets depending upon the

strength of the current. Polarity of the magnetic field which causes these bar magnets depends on

the change of current. Decreasing current will cause NS magnet and vice versa. Power of these

magnets is as per BH curve. Thus the magnetic flux strengthens the unarranged magnetic particles as

per the signal and they stay in that condition after the tape has already passed the

magnetic head (fig. 2). Length of the magnet thus formed is directly proportional to

writing speed of the head v, and inversely proportional to the frequency of the signal to be

recorded, i.e.

Recorded wavelength for one cycle of signal = speed x time

Or Wave length of the magnetic signal tape = v / f

Recording Process

the problem to be solved in the development of VTRs was how to provide higher speed to record

very high frequencies.

The other limitation of recording medium is the range, during when the extracted signal is more

than noise. This range is only 10 octaves. Thus the system can no longer be used

for recording/reproduction after this dynamic range of 60 db, because of 6 dB/octave

playback response characteristics. Beyond this range the low frequencies becomes inaudible and the

higher frequencies become distorted.

During the initial stages it was tried to record video signal with stationary video heads

and longitudinal tracks using tape speed of the order of 9 m/s which was very difficult

to control besides very high tape consumption i.e, miles of tape for 3 to 4 minutes of recording and

this was coupled with breaking of video signal frequencies into 10 parts recorded by 10

different video heads and then switched during playback to retrieve the signal. The

quality of the reproduced signal was also compromised up to the resolution of 1.7 MHz

or so. Around 1956 the ‘AMPEX' company of USA then came out with Quadruplex machines

having two revolutionary ideas which laid the foundation of present day VTRs/VCRs.



46 | P a g e

These ideas were:

1. Rotating Video Heads and

2. Frequency Modulation before recording

Increase in writing speed by rotating head

When a video head mounted on a rotating head wheel writes on a tape moving across it, will lay a

track of length which will depend not only on the speed of the tape but also on the rotating speed of

the head. Single head with diameter d number of rotation per sec as r and full omega wrap or two

heads in ½ omega wrap i.e. little over 180 degree, which most of the present day VCR are using, will

have a writing speed of dr minus or plus the linear tape speed (which is negligible as compared to

the rotating speed). This avoids the requirements of miles of tape for few minutes of recording in a

stationary head type of recorders tried earlier.

Monitoring During Recording

Most of the video tape recorders provide Electronics to Electronics monitoring (EE Mode) at the time

of recording. The video signal is monitored after routing it through all the signal system electronics

of the recorders excluding the video heads and preamplifiers etc. Some of the recorders also provide

simultaneous playback for the off tape monitoring by using additional heads during recording called

confidence heads.

Thus the VTRs could achieve wider frequency range with:

a) Faster writing speed

b) Smaller gap, and

c) Octave band compression with frequency modulation.

Also achieving accurate speed for motors with servo system reduces the timing errors.

Playback process

During play back when the recorded tape is passed over the head gap at the same speed at which it

was recorded, flux lines emerging from the tape on crossing the head gap induce voltage in the coil

proportional to the rate of change of flux, i.e. d /dt and this in turn depends on the frequency of the

recorded signal. Doubling of frequency causes voltage to increase by 6 dB. This

accounts for the well known 6 dB/octave playback characteristics of the recording medium. This

holds good only up to a certain limit thereafter at very high frequencies, lot of losses take place

during playback and recording process causing noise to be more than the signal itself. It may be

noted that when the gap becomes equal to the wavelength of the recorded signal, two adjoining bar

magnets may produce opposite current during playback and the output becomes zero.

Similar thing happens when the gap equals 2, 3 …n. times the wavelength. First extinction

frequency occurs when gap becomes equal to wavelength. For getting maximum output,

head gap has to be one half of wavelength.

Frequency at which zero output occurs is called extinction frequency . Thus the maximum

usable frequency becomes half of the extinction frequency. These parameters are related by:



47 | P a g e

Playback Process

So in order to record the higher frequencies we must increase the writing speed for a minimum

value of wave length recorded on tape i.e. tape. This minimum value of tape is again restricted

by the minimum practically possible head gap.

Now the ratio of video and audio frequencies is approximately 300, so we must increase the

writing speed or reduce the gap by the same factor of 300 to get the desired results. Perhaps a

speed of 60 mph will be required to cope with the higher video frequencies.

VIDEO TAPE FORMATS-

INTRODUCTION

Format of Video tape recorder defines the arrangement of magnetic information on the tape. It

specifies:

1. The width of tape,

2. Number of tracks for Video, Audio, Control, time code and cue,

3. Width of tracks,

4.Their electrical characteristics and orientation.

All machines conforming to one format have similar parameters to enable compatibility or

interchange i.e. the tape recorded on one machine is faithfully reproduced on the other. There

are a number of formats in Video tape recording and the number further gets multiplied due to

different TV. Standards prevailing in various countries e.g. PAL, SECAM, NTSC and PAL-M.

CLASSIFICATION OF FORMAT:

A) Analog Formats:

VTRs using composite Video for professional Broadcast use were , Quadruplex 2” , 1" format and

C ( All reel/Spool Type) which were then replaced by U- matic cassette recorders followed by

best quality analog format with separate luminance & chrominance recording called component

Analog formats. These were Betacam SP from SONY & M-II from Panasonic.

a) Quadruplex Format (Segmented)

This was the first professional broadcast video tape recorder introduced by AMPEX in 1956 and

has since been replaced by 1" recorders of type B and type C formats. This format uses spool of

2" wide tape, 4 heads on transversely mounted drum, with a very high writing speed of about

41m/s. These machines had higher operational cost and required constant



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engineering efforts to keep them running. These machines have since been phased out except

for transfer/archival purpose.

b) Type B Format (Segmented helical)

This format was developed by BOSCH/BTS using helical scan with 1" tape as BCN series of Video

Tape recorders. It uses a scanner with head wheel carrying two video heads around which tape

is wrapped in about 190o. Each television field is recorded on six tracks with each head

scanning a 52 line segment. The scanner diameter is 50mm and rotates at 150

rev/sec. The tape moves at 24cms/sec. The 80 mm long tracks are recorded at an angle of

14.3o. There are four longitudinal tracks out of which two are full quality audio tracks, third for

the time code and the fourth for the control track. Video writing speed is 24m/s. The

flying erase head mounted on the same head- wheel and the associated electronics

allows for roll free electronic editing. The addition of digital frame store unit provides freeze

frame and slow motion. The portable version in the same format has also been marketed by the

manufacturers for studio use.

c) Type C Format (field per scan helical)

This is the combined format of AMPEX and SONY using 1" tape with a full omega wrap around a

helical scanner running at 50 rps. Main head mounted on a 135 mm dia drum records one field

i.e.

B). DIGITAL FORMATS

Modern television post production demands multi-layer special effects with several

manipulations having first generation quality. This requires multi-generation playback & a

transparent recordings from Video cassette players./recorders. which can be met only by the

digital formats without loss in picture quality.

Digital Composite/Component Formats

A) D1 format was the first DVTR not to compromise on the technical quality in

any way. It is based on 4:2:2 sampling structure of CCIR-601, completely

transparent in quality but very expensive and bulky. Still it is considered as reference

machine for digital formats and known as father of all digital formats.

It uses 3/4" tape & has a writing speed of about 30m/s.Its drum is running at 150

rps with segmented tracks. Digital coding is in 8-bit words with a raw picture data rate of 216

Mbps.

b) D2 format was the first economical DVTR based on CCIR - 601, 4 fsc sampling on composite

video. It offered easy interface to a composite world at a reasonable cost. It was soon

overshadowed by the then forthcoming D 3 format.

c) D3: D3 was developed by NHK and Panasonic using composite system, 1/2" metal particle

VHS sized cassette thus saving cost. It records 8 bit digital video at a sampling rate of 4 fsc

(17.73MHz) in 8 tracks per field. Data rate is similar to D2.

d) D4: 4 is perhaps an unlucky number in Japan as there is no D4.

e) D5: Panasonic's new component system D5 is a successor to D3. It is digital component

using same cassettes as D3 but running at double speed. In addition to all the

usual facilities, D5 can playback existing D3 tapes. It gives just 2 hours from a

long size cassette. Coding is 10-bit with luminance sampling at 13.5 MHz. D5 can handle

4:3 or 16:9 aspect ratio with full restoration. For 16:9, sampling rate is 18 MHz with 8-bit coding

Based on CCIR 601. It is without any data compression.



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Digital Betacam:

It is based on CCIR 601, and allows 16:9 upgrades. To reduce data rate it uses Bit Rate reduction

(BRR).Bit rate reduction is in the ratio of 2:1. This has been made possible because of the

conversion of data from time domain to frequency domain and removing the redundancy from

the digital video data. Equivalent system without BRR would have required more tape speed,

extra thin tape, and extra narrow tracks and would have also needed double the number of

heads on drum or double the drum speed. It is compatible with Betacam SP and is having 4 PCM

Digital Audio Track. Scanner for this machine is larger then that of Betacam SP but the helix is

such that when rotated at frame rate ,track angle of analog Betacam is traced .This gives a time

compressed replay is which is then expanded in TBC. For digital Betacam, to handle large data

the scanner speed is increased to 3 times. One field is recorded in one and half revolution in 6

tracks of 26 Micrometers each.

BETACAM VIDEO CASSETTE RECORDERS-

INTRODUCTION:

Betacam series of VCRs are based on analog component system. These VCRs had become

popular because of their low initial and running costs in comparison to B and C Format

machines. The quality of reproduction of Betacam SP was near to these analog formats. Betacam

format was introduced in 1982 followed by Betacam SP in 1987. Popular Betacam SP VCRs

which are being replaced with digital VCRs in doordarshan are:- BVW 75P - SP Recorder cum

player, with DT head (Slow motion heads for dynamic tracking) & PVW 2800P PRO SERIES

besides camcorder and portable version of this format .

Head drum :

Head drum for BVW 75P carries as many as 10 video heads, two heads for Luminance Ya, Yb,

two heads for chrominance Ca, Cb, two heads for Dynamic tracking Luminance DTYa, DTYb, two

heads for Dynamic tracking chrominance DT Ca, DT Cb, and finally two heads for Eraser REa &

REb (Rotary erase). In some of the models where slow motion is not available DT heads and

associated electronics is not required. This makes those models cheaper to BVW 75P.



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VIDEO SYSTEM

Video system is based on component analog system. Composite video is decoded into its

component, Luminance Y and colours as R-Y & B-Y. You may note that these colour signal are

base band signal and have nothing to do with 4.43MHz subcarrier frequency. Y is recorded

directly after FM on one of the video tracks by Ya & Yb head. Chrominance signals are first

compressed as CTDM signal (Compressed time division multiplexing) and then frequency

modulated. This FM chroma is then mixed with AFM audio channel 3 & 4 before it is recorded

along with chrominance information.

TAPE TRANSPORT FOR PVW SERIES OF BETACAM SP



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DIGITAL VIDEO CASSETTE RECORDER PROFESSIONAL (DVCPRO)-

INTRODUCTION

With the advent of digital signals, breakthrough came in the field of recording from

analog recording to digital recording around the year 1990. In the series of

development of digital tape recording systems, it is felt to have a system which

should be handy for the purpose of field recording along with capability of long

duration recording. A recording format is developed by a consortium of ten companies

as a consumer digital video recording format called “DV”. DV (also called ”mini DV” in its

smallest tape form) is known as DVC (Digital Video cassette). DVCAM is a professional variant of

the DV, developed by Sony and DVCPRO on the other hand is a professional variant of the

DV, developed by Panasonic. These two formats differ from the DV format in terms of

track width, tape speed and tape type. Before the digitized video signal hits the tape, it is the

same in all three formats.

What is DV? DV is a consumer video recording format, developed by a consortium of 10

companies and later on by 60 companies including Sony, Panasonic, JVC, Phillips etc., was

launched in 1996. in this format, video is encoded into tape in digital format with intra frame



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DCT compression using 4:1:1 chroma subsampling for NTSC (or 4:2:0 for PAL). This makes it

straightforward to transfer the video onto computer for editing due to its intra frame

compression technique. DV tapes come in two formats: MiniDV size (66mm x 48mm x 12.2mm)

and DV, the standard full size (125mm x 78mm x 14.6mm). They record digital compressed

video by a DCT method at 25 Megabit per second. In terms of video quality, it is a

step up from consumer analog formats, such as 8mm, VHS-C and Hi-8.

What is DVCPRO?

DVCPRO is a professional variant of the DV, developed by Panasonic. In DVCPRO,

the baseband video signal is converted to 4:1:1 sampled data sequence from the originally

sampled 4:2:2 signal by the method of subsampling and the resulted data are converted into

blocks which are shuffled before passing through compression circuitry and again reshuffled

back to their original position after compression. It is to mention here that still

pictures containing little or no movement are compressed using intra frame compression

whereas the pictures with large amounts of movements are coded and compressed in intra field

form. Error correction code is added to the compressed and reshuffled data sequence by

using Reed Solomon product code before it is sent to recording modulation method.

The modulated data sequence generated by 24-25 coding method using scrambled

NRZI is recorded onto the tape via video head.

Within the DV(Digital Video) format, audio can be recorded in either 2 channel (1 left and 1

right) or 4 channel mode (2 stereo pairs). In the DVCPRO format the audio is 2

channel record mode only, though provision is made to replay 4 channel type DV

tapes. It is to mention here that audio data is recorded un-compressed.

2 Channel Audio Record Mode

The audio signal is digitized by sampling the analog audio signal with 48 kHz

sampling frequency and quantized the samples by 16-bit linear quantizer. In PAL

(625/50 Hz) DVCPRO system, one frame of video occupies 12 tracks on the tape. One frame

corresponds to 40 milliseconds(25 frames/sec implies 1 frame/40 msec). So 40

milliseconds of audio data (per channel) is recorded into 12 track frame period. At 48kHz

sampling frequency, 1920 samples are generated in 40 msec(40 x 48 = 1920) which

have to be accommodated in 6 tracks. DVCPRO format fix the first six tracks for data belonging

to the channel 1 input and the second six tracks for data belonging to channel 2. Each track

contains 1920/6 = 320 samples(320 x 16 bits = 640 bytes) which can be

memorized in 9 x 72 matrix in processing module.



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VISION MIXING

Introduction

Vision mixing is a process of creating composite pictures from various sources.

Vision mixing involves basically three types of switching or transitions between various sources.

These are mixing, wiping and keying. These transitions can also be accompanied by special

effects in some of the vision mixers.

Mixing

Two input sources are mixed in proportion in a summing amplifier as decided by

the position of control fader. Two extreme position of the fader gives either of the sources at the

output. Middle of the fader gives mixed output of the two sources; control to the

summing amplifier is derived from the fader.

Wipe

In this case the control for the two input sources is generated by the wipe pattern

generator (WPG), which can either be saw tooth or parabola at H, V or both H &

V rate. Unlike in MIX, during WIPE, one source is present in one side of the wipe and the

second source on other side of the wipe. A very simple to very complex wipe

patterns can be generated from the WPG.

Key

In the Key position between two sources i.e. foreground (FG) and background (BG)

the control derived from one of the source itself (overlay), or by the third source

(external key). This keying signal can be generated either by the luminance, Hue or

chrominance of the source input. The keyed portion can be filled with the same or with matte or

external source. Matte means internally generated BG with choice of colors from the vision

mixer.



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NON LINEAR EDITING & 3-D GRAPHICS-

INTRODUCTION

Fundamentally editing is a process where one places Audio video clips in an appropriate

sequence and mainly used in video post production. Linear editing is tape based and is

sequential in nature. It has various problems like long hours spent on rewinding of tapes in

search of material, potential risk of damage to original footage, difficult to insert a new shot in

an edit, difficult to experiment with variations, quality loss is more, limited composting effects

and color correction capability. Non-linear editing (NLE) is a video editing in digital

format with standard computer based technology. NLE can also be extended to film editing.

Computer technology is harnessed in Random access, computational and manipulation

capability, multiple copies, multiple versions intelligent search, sophisticated project

and media management tools, standard interfaces and powerful display.

ADVANTAGES OF NLE

NLE has various advantages over tape based (linear) editing.

Flexibility in all editing functions.

Easy to do changes, undo, copy, duplicate and multiple version.

Easy operation for cut, dissolve, wipes and other transition effects.

Multi-layering of video is easy.

Powerful integration of video and graphics, tools for filtering, color correction, key

framing and special 2D/3D effects.

Equally powerful audio effects and mixing.

Possible to trim ; compress or expand the length of the clip.

Intelligent and powerful 3D video effect can be created and customized.

Efficient and intelligent storage.



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BREAKOUT BOX-

Various video sources like VTR, CD player, camera and other playback/recording devices are

connected to NLE machine through breakout box. The NLE machine takes input from various

video sources for editing and gives output for monitoring and recording through break out box.

INPUTS

Video Inputs

There are three analog inputs (1) Component Video (2) S-Video (3) Composite video

Audio Inputs

To capture synchronized audio with your video, you must connect audio out from the VTR or

other play back device to the audio inputs. You can also connect audio only devices for sound

track production etc. the dps reality board (NLE hardware) has three analog audio options ;

balanced, unbalanced and Aux.



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Time Code

Time code is simply a series of labels attached to a recording at timed intervals, generally

fractions of sounds. Each label contains a time of recording. Time code is used for editing; in

order to be able to return repeatedly to a selected time, and for synchronization among audio

and video recorders and players. The two versions of time code that are available with dps

OUTPUTS

Video Output

Component (CAV) Video has three connectors, labeled Y, B-Y, R-Y. A cable connects each of these

three outputs to your video monitor or VTR.

Audio Output

Choose what type of video to output based on whether your VTR and other video and audio

equipment can receive balance or unbalance audio. Audio out is connected to speakers for

playback or to a VTR or other audio recording device during recording.



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3 –D GRAPHICS

THE FIVE MODULES OF SOFTIMAGE

Softimage 3 D Extreme has given different modules that correspond to different

phases of the workflow process you use to create animation. Each of the modules replaces

some of the menu cells on the left and right menu columns, while leaving other menu

cells that are applicable in all modules. The modules are listed along the top right

corner of the screen: Model, Motion, Actor, Matter, and Tools. You can enter these

modules either by clicking the text labels in the top right corner, or by pressing the

supra keys that represent them: F1 for Model, F2 for Motion, F3 for Actor, F4 for Matter, and F5

for Tools.

MODEL

You start your workflow in the Model module, where you construct all your scene

elements. Model's tools enable you to create objects from primitive shapes, draw

curves, and develop surfaces from those curves.

MOTION

You then move to animate some parts of your scene, using the animation tools found in the

Motion module. The Motion module allows you to set animation keyframes for

objects, assign objects to paths, and to see and edit the resulting animation on screen. After

you have refined your animation using the F Curve tools, you move to the next module, Actor.

ACTOR

The Actor module contains the special Softimage tools for setting up virtual actors,

assigning inverse kinematic skeletons, assigning skin, adjusting skeletons deformations, and

weighting the skin to the IK skeletons. Actor also contains the controls for physical-based

animation–Dynamics,Collisions and Qstretch–which is an automatic squash-and-stretch

features.

MATTER

When your modeling, animation, and acting are complete, you move to the fourth module:

Matter. In the Matter module, you assign color and material values to the objects in your scene,

determining how they will look in the final render.



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At any time in the first four modules, you can create lights and adjust their effect on the scene.

The Matter module is also where you perform the last step in the workflow process, rendering.

TOOLS

Tools contains a variety of utility programs for viewing, editing and exporting your work. You

may view individual images, sequences of images, and line tests. You may bring in images

created in other programmes as image maps or import objects created in other programs as

geometry. You can composite sequences of images together, reduce colours in sequences of

images for reduced colour games systems, and move your finished work to video disk recorders

and film recorders.

The Four View Windows



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TELEVISION TRANSMISSION

VESTIGIAL SIDE BAND TRANSMISSION - If normal amplitude modulation technique is used

for picture transmission, the minimum transmission channel bandwidth should be

around 11 MHz taking into account the space for sound carrier and a small guard band of

around 0.25 MHz. Using such large transmission BW will limit the number of channels

in the spectrum allotted for TV transmission. To accommodate large number of

channels in the allotted spectrum, reduction in transmission BW was considered

necessary. The transmission BW could be reduced to around 5.75 MHz by using single side band

(SSB) AM technique, because in principle one side band of the double side band (DSB) AM could

be suppressed, since the two side bands have the same signal content.

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

units both at base band as well as at IF stage, so that after passing through all subsequent

transmitter stages, an acceptable signal is available. Since the number and type of amplifier

stages, may differ according to the required output power, the characteristics of the pre-

correction circuits can be varied over a wide range.

Block Diagram of TV Exciter (Mark-II)

Vision and Sound Signal Amplification

In HPTs the vision and sound carriers can be generated, modulated and amplified separately

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 more

prominent and special filters for suppressing them is required.As it is difficult to meet the

intermodulation requirements particularly at higher power ratings, separate



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amplification is used in HPTs though combined amplification requires fewer amplifier

stages.

IF Modulation

It has following advantages

1. Ease of correcting distortions

2. Ease in Vestigial side band shaping

3. IF modulation is available easily and economically

Power Amplifier Stages

In BEL mark I & II transmitters three valve stages (BEL 450 CX, BEL 4500 CX and BEL 15000

CX) are used in vision transmitter chain and two valves (BEL 450 CX and BEL 4500 CX) in aural

transmitter chain. In BEL mark III transmitter only two valve stages (BEL 4500 CX and BEL

15000 CX) are used in vision transmitter chain. Aural transmitter chain is fully solid state in

Mark III transmitter.

Constant Impedance Notch Diplexer (CIND)

Vision and Aural transmitters outputs are combined in CIN diplexer. Combined power is fed to

main feeder lines through a T-transformer.

BEL 10 kW TV TRANSMITTER (MARK-II)

Block Diagram of BEL 10kW TV Transmitter (Mark-II)

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 two independent

system viz.

1. Main control system. (MCS)

2. Back-up Control System (BCS)



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Functions performed by MCS (Main Control System)

- XTR control

- Interlocking

- RF monitoring

- Supporting operation from control console

- Three second logic for protection against sudden fluctuation.

- Thermal protection for 1 kW and 10 kW vision PAs

- Thermal protection for 130 Watt vision PA and Aural XTRa

- Mimic diagram

Functions performed by BCS (Backup control system)

- Transmitting control

- Interlocking

The block diagram of the TCU (Transmitter control unit) indicates the connectivity

of TCU with control console and the control elements of the transmitter. Commands are

inputs through the key board. The control elements are controlled in accordance with

the programme fused in the EPROMS.

Only while operating from the MCS (Main Control System), the interaction with TCU is

supported through a LCD display unit. The LED bar display board showing the status

information, is used by both the MCS and BCS (Back up Control Unit).

Main Control System (MCS) The MCS consists of the following :

1. Mother Board with the following PCBs.

CPU

BIT I/O

Interlock Interface Board (IIB).

Analog I/O Board (AIO)

Control Interface Board (CIB)

Analog Receiver Board (An Rx)

Rectifier and Regulator Board (RRB mcs)

2. Key Board

3. LED Bar Display Board

4. Relay Board

5. LCD Display Unit

6. Transformers T1 and T2 .

7. + 5V/3A. Power Supply Unit.



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TV TRANSMITTER

Antenna System is that part of the Broadcasting Network which accepts RF Energy

from transmitter and launches electromagnetic waves in space. The polarization of the

radiation as adopted by Doordarshan is linear horizontal. The system is installed on a

supporting tower and consists of antenna panels, power dividers, baluns, branch feeder cable,

junction boxes and main feeder cables. Dipole antenna elements, in one or the other form are

common at VHF frequencies where as slot antennae are mostly used at UHF frequencies. Omni

directional radiation pattern is obtained by arranging the dipoles in the form of turnstile

and exciting the same in quadrature phase. Desired gain is obtained by stacking the

dipoles in vertical plane. As a result of stacking, most of the RF energy is directed in the

horizontal plane. Radiation in vertical plane is minimized.

The installed antenna system should fulfil the following requirements :

a) It should have required gain and provide desired field strength at the point of reception.

b) It should have desired horizontal radiation pattern and directivity for serving the planned area of

interest. The radiation pattern should be omni directional if the location of the transmitting station is

at the center of the service area and directional one, if the location is otherwise.

c) It should offer proper impedance to the main feeder cable and thereby to the transmitter so that

optimum RF energy is transferred into space. Impedance mismatch results into reflection of power

and formation of standing waves. The standard RF impedance at VHF/UHF is 50 ohms.



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Outdoor Broadcasting Van (OB Van)

O B Van (Outdoor Broadcasting van )- OB van is used for live broadcasting like any match or any

event. It consist all the equipments that is present in the studio for telecasting. It also referring as

mini studio . It has mainly 3 parts :

1)Power supply unit

2)Production control unit

3)Audio console and VTR

Inner View of OB van

Inner View of OB van



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EARTH STATION

SATELLITE COMMUNICATION Satellite Communication is the outcome of the desire of man to achieve the concept of global village.

Penetration of frequencies beyond 30 Mega Hertz through ionosphere force people to think that if

an object (Reflector) could be placed in the space above ionosphere then it could be possible to use

complete spectrum for communication purpose.

Intelsat-I (nick named as Early Bird) was launched on 2 April 1965. This was parked

in geosynchronous orbit in Atlantic ocean and provided telecommunication or

television service between USA and Europe. It had capacity for 240 one way telephone

channels or one television channel. Subsequently Intelsat-II generation satellites were launched

and parked in Atlantic ocean and Pacific Ocean. During Intelsat III generation, not only Atlantic and

Pacific ocean got satellites but also Indian Ocean got satellite for the first time. Now Arthur

C.Clarke's vision of providing global communication using three Satellites with about 120 degrees

apart became a reality. So far Intelsat has launched 7 generations of geosynchronous

satellites in all the three regions namely Atlantic Ocean, Pacific Ocean and Indian Ocean.

For national as well as neighbouring countries coverage, some of the following satellites are used:

ANIK : Canadian satellite system I

NSAT : Indian Satellites

AUSSAT : Australian Satellites

BRAZILSAT : Brazilian Satellites

FRENCH TELECOM : French Satellites

ITALSAT : Italian Satellites

CHINASAT : Chinese Satellites

STATSIONAR, GORIZONT, Russian Satellites

Architecture of a Satellite Communication System

The Space Segment

The space segment contains the Satellite and all terrestrial facilities for the control and monitoring of

the Satellite. This includes the tracking, telemetry and command stations (TT&C) together with the

Satellite control centre where all the operations associated with station-keeping and checking the

vital functions of the satellite are performed. In our case it is Master Control Facility (MCF) at

Hassan.

The radio waves transmitted by the earth stations are received by the satellite ; this is called the up

link. The satellite in turn transmits to the receiving earth stations ; this is the down link. The quality

of a radio link is specified by its carrier-to-noise ratio. The important factor is the quality of the total

link, from station to station, and this is determined by the quality of the up link and that of the down

link. The quality of the total link determines the quality of the signals delivered to the end user in

accordance with the type of modulation and coding used.



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The Ground Segment

The ground segment consists of all the earth stations ; these are most often connected to the

end- user's equipment by a terrestrial network or, in the case of small stations (Very

Small Aperture Terminal, VSAT), directly connected to the end-user's equipment.

Stations are distinguished by their size which varies according to the volume of traffic to be

carried on the space link and the type of traffic (telephone, television or data). The largest are

equipped with antenna of 30 m diameter (Standard A of the INTELSAT network). The

smallest have 0.6 m antenna (direct television receiving stations). Fixed,

transportable and mobile stations can also be distinguished. Some stations are both

transmitters and receivers.

Space Geometry

Types of Orbit

The orbit is the trajectory followed by the satellite in equilibrium between two

opposing forces. These are the force of attraction, due to the earth's gravitation, directed

towards the centre of the earth and the centrifugal force associated with the curvature

of the satellite's trajectory. The trajectory is within a plane and shaped as an ellipse with a

maximum extension at the apogee and a minimum at the perigee. The satellite moves more

slowly in its trajectory as the distance from the earth increases.

Most favourable Orbits

Elliptical orbits inclined at an angle of 64o with respect to the equatorial plane. This orbit

enables the satellite to cover regions of high latitude for a large fraction of the orbital period as

it passes to the apogee. This type of orbit has been adopted by the USSR for the

satellites of the MOLNYA system with a period of 12 hours. Please note that the satellite

remains above the regions located under the apogee for a period of the order of 8 hours.

Continuous coverage can be ensured with three phased satellites on different orbits.



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Circular inclined orbits :

The altitude of the satellite is constant and equal to several hundreds of kilometers. The period

is of the order of one and a half hours. With near 90% inclination this type of orbit guarantees

that the satellite will pass over every region of the earth. Several systems with world wide

coverage using constellations of satellite carries in low altitude circular orbits are for e.g.

IRIDIUM, GLOBAL STAR, ODYSSEY, ARIES, LEOSAT, STARNET, etc.

Circular orbits

with zero inclination (Equatorial orbits). The most popular is the geo stationary satellite orbits ;

the satellite orbits around the earth at an altitude of 35786 km, and in the same direction as the

earth. The period is equal to that of the rotation of the earth and in the same direction. The

satellite thus appears as a point fixed in the sky and ensures continuous operation as a radio

relay in real time for the area of visibility of the satellite (43% of the earth's surface).

Factors deciding the selection of Orbit

The choice of orbit depends on the nature of the mission, the acceptable

interference and the performance of the launchers :

The extent and latitude of the area to be covered.

The elevation angle of earth stations.

Transmission duration and delay.

Interference

The performance of launchers

TVRO System

Presently Doordarshan is up linking its national, metro and regional services to INSAT-2A (74oC) and

INSAT-2B (93.5oE) and INSAT 2E (83o C). Down link frequency bands being used are C-Band (3.7-4.2

GHz) and Ex-C Band (4.5-4.8 GHz).

Transmission of base band to Satellite

The base band signal consists of video (5 MHz), two audio subcarriers (5.5 MHz & 5.75 MHz) and

energy dispersal signal (25 Hz). After modulation (70 MHz) and upconversion (6 GHz) the carrier is

amplified and uplinked through Solid Parabolic Dish Antenna (PDA). Down link signal can be received

through same PDA using Trans-Receive Filter (TRF) and Low Noise Amplifier (LNA). After down

conversion to 70 MHz, it is demodulated to get audio and video.



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Satellite Transponder

As shown in fig, the uplinked signal (6 GHz) at satellite is received, amplified and down converted to

4 GHz band and sent back through filter and power amplifier (TWT). The local oscillator frequency of

down converter is 2225 MHz for C band and Ex-C band transponders.

Block Diagram of Satellite Transponder

Receiving Satellite Signal

For receiving a satellite signal we need following equipment :

1. Satellite receiving antenna (PDA).

2. Feed with low noise block converter (LNBC).

3. Indoor unit consisting of satellite system unit and a Synthesised satellite receiver.

Parallels of Latitudes Latitude as Angular Distance



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Direct-to-Home Satellite Broadcasting (DTH)

INTRODUCTION

There was always a persistent quest to increase the coverage area of broadcasting.

Before the advent of the satellite broadcasting, the terrestrial broadcasting, which is

basically localized, was mainly providing audio and video services. The terrestrial broadcasting has

a major disadvantage of being localized and requires a large number of transmitters to cover a big

country like India. It is a gigantic task and expensive affair to run and maintain the large number of

transmitters. Satellite broadcasting, came into existence in mid sixties, was thought to

provide the one-third global coverage simply by up-link and down-link set-ups. In the

beginning of the satellite broadcasting, up-linking stations (or Earth Stations) and satellite

receiving centers could had only been afforded by the Governments organizations. The main

physical constraint was the enormous size of the transmitting and receiving parabolic

dish antennas (PDA). In the late eighties the satellite broadcasting technology had

undergone a fair improvements resulting in the birth of cable TV. Cable TV operators set

up their cable networks to provide the services to individual homes in local areas. It rapidly grew

in an unregulated manner and posed a threat to terrestrial broadcasting. People are now

mainly depending on cable TV operators. Since cable TV services are unregulated and unreliable in

countries like India now, the satellite broadcasting technology has ripened to a level where

an individual can think of having direct access to the satellite services, giving the

opportunity to viewers to get rid of cable TV. Direct-to-Home satellite broadcasting (DTH) or Direct

Satellite Broadcasting (DBS) is the distribution of television signals from high powered

geo- stationary satellites to a small dish antenna and satellite receivers in homes across the country.

The cost of DTH receiving equipments is now gradually declining and can be afforded by common

man. Since DTH services are fully digital, it can offer value added services, video-on-demand,

Internet, e- mail and lot more in addition to entertainment. DTH reception requires a small dish

antenna (Dia 60 cm), easily be mounted on the roof top, feed along with Low Noise Block Converter

(LNBC), Set- up Box (Integrated Receiver Decoder, IRD) with CAS (Conditional Access System). A

bouquet of 40 to 50 video programs can simultaneously be received in DTH mode.

UPLINK CHAIN

DTH broadcasting is basically satellite broadcasting in Ku-Band (14/12 GHz). The main advantage of

Ku-Band satellite broadcasting is that it requires physically manageable smaller size of

dish antenna compared to that of C-Band satellite broadcasting. C-Band broadcasting requires about

3.6 m dia PDA (41dB gain at 4 GHz) while Ku-Band requires 0.6 m dia PDA (35dB gain at 12 GHz). The

shortfall of this 6 dB is compensated using Forward Error Correction (FEC), which can offer 8 to 9 dB

coding gain in the digital broadcasting. Requirement of transmitter power (about 25 to

50 Watts) is less than that of analog C-band broadcasting. The major drawback of

Ku-Band transmission is that the RF signals typically suffer 8 to 9dB rain attenuation under heavy

rainfall while rain attenuation is very low at C-Band. Fading due to rain can hamper

the connectivity of satellite and therefore rain margin has to be kept for reliable connectivity. Rain

margin is provided by operating transmitter at higher powers and by using larger size of the dish

antenna (7.2m PDA). Fig.1 shows schematic of uplink chain proposed to broadcast

bouquet of 30 video programs in Doordarshan, Prasar Bharati, India. 30 video programs may



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either be down-linked from satellites or taken from other sources like video tape recorders, video

cameras etc. in digital format. These sources are fed to Router whose outputs are divided in three

groups A, B and C. Each group contains 10 video sources multiplexed in a Multiplexer. These three

multiplexed streams are digitally (QPSK modulation) modulated individually at 70 MHz Intermediate

Frequency (IF). Each group is further doubly up-converted, first conversion at L-Band (950-1450

MHz) and second conversion at Ku-Band (12-14 GHz).

DOWN-LINK CHAIN

Down-Link or receiving chain of DTH signal is depicted in Fig.2. There are mainly three

sizes of receiving antenna, 0.6m, 0.9m, and 1.2m. Any of the sizes can easily be

mounted on rooftop of a building or house. RF waves (12.534GHz, 12.647GHz, 12.729 GHz) from

satellite are picked up by a feed converting it into electrical signal. The electrical signal is

amplified and further down converted to L-Band (950-1450) signal. Feed and LNBC are

now combined in single unit called LNBF. The L-Band signal goes to indoor unit, consisting a

set-top box and television through coaxial cable. The set-top box or Integrated Receiver

Decoder (IRD) down converts the L-Band first IF signal to 70 MHz second IF signal,

perform digital demodulation, de-multiplexing, decoding and finally gives audio/video output

to TV for viewing.



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doordarshan patna summer training

Engineering

amal roshan b

yusuf sir amal roshanmd

constituents of prasar

summer training report

guidance of

terms of prasar bharati

year of b

completion of summer