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CHAPTER 1
INTRODUCTION
Training is important phase of student life. During this period student gets both theoretical as well as practical knowledge of the subject. Training also impresses a student overall approaches to life and impress his personality and confidence.
Our training was in Doordarshan Kendra Lucknow. This report contains a detailed
study of Doordarshan Kendra Lucknow.
There are 3 divisions here:1 Studio
2 Transmitter
3 Earth Station
1.1 STUDIO
Doordarshan is a leading broadcasting service provider in india. DD Lucknow is fullflathead broadcast set up. Many serials &program are being made here like "BIBI
NATIYON WALI", "NEEM KA PED" and "HATIM TAI" etc. recorded in studio.
1.2 TRANSMITTER
Here the transmission of both audio and video has been made. The transmission section does the function of modulation of signal. Power amplification of the signal &
mixing of audio and video signal is done here.
1.3 EARTH STATION
The main function of earth station is to make contact with satellite or communicate
with it. The signals from other transmitter are down linked here.
Also the signals here are uplinked to send it to larger distance.

1

CHAPTER 2
FUNDAMENTALS OF
MONOCHROME &
COLOUR TV SYSTEM

Fig 2.1 TV Transmission Model
2.1 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 scjanned 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 Hert.
2.2 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.

2

2.3 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)
2.4 GREY SCALE
In black and white (monochrome) TV system all the colours appear as gray on a 10step 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 eyes capability is much more).
2.5 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).
2.6 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.
2.7 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.

3

CHAPTER 3
COLOUR COMPOSITE VIDEO SIGNAL (CCVS)
3.1 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 picture per sec our eyes
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 particles known as Pixels.
These pixels 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 signal 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 figure.

Fig 3.1 Colour Composite Video Signal

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3.2 FREQUENCY CONTENT OF TV SIGNAL
The TV signals have varying frequency 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 5 MHz 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 TV is a medium of close ups and mid close ups.
3.3 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.

Fig 3.2 Seperation of H & V Sync Pulses from CCVS
3.4 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 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.
AM produces double side bands. The information is the same in both side bands. It is
enough to transmit single side band only. Carrie r also need not be transmitted in
full and a pilot carrier can help.

5

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
3.5 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 the region of the vestigial side band do not appear with
double amplitude after detection. For this purpose the IF curve..
employs NYQUIIST slope.

Fig 3.3

Receiver Pass Band Characterstics

6

5

3.6 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).
3.7 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

Fig. 3.4 Additive Colour Mixing

7

CHAPTER 4
TV CAMERA

Fig 4.1 Camera

4.1 INTRODUCTION:
A TV Camera consists of three sections.
4.1.1 A Camera lens & Optics: To form optical image on the face plate of a pick up
device
4.1.2 A transducer or pick up device: To convert optical image into a electrical signal
4.1.3 Electronics: To process output of a transducer to get a CCVS signal
4.2 TYPES OF PICK - UP DEVICES
There are three types of pick up devices based on :
4.2.1 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.
4.2.2 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. Im-

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provement in these cameras lead to the development of Plumb icon and Sat icon
cameras.
4.2.3 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 .
4.3

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:
4.3.1 FRAME TRANSFER (FT).
4.3.2 INTERLINE TRANSFER (IT).
4.3.3 FRAME INTERLINE TRANSFER (FIT).
4.4 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.
4.5 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
9

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.
4.6 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 (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 micro lens 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 ƒstop of extra sensitivity has been realized.

Fig 4.2 Optical block for Video Camera

10

4.7 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 prepre 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 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.

11

CHAPTER 5
TV LIGHTING
5.1 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.,
wave length 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

5.1.1 Light Source: Any light source has a Lumnance intensity (I) which is
measured in Candelas. One Candela is equivalent to an intensity released by standard one candle source of light.

5.1.2 Luminance flux (F): It is a radiant energy weighted by the photonic curve & is measured in Lumens.
One Lumen is the luminous flux emitted by a point source of 1 Candela.

5.1.3 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.

5.1.4 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 Apostilbs.
5.2 COLOUR TEMPERATURE:
One may wonder, how the light is associated with colour . 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
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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 determyined. All the color temperature meter are based on this principle.
5.3 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 filters :
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.
5.3.1 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.

13

5.4 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
5.5 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 plan, a
console should provide :
5.5.1 One man operation and a centralized control desk with ability to switch
any circuit.
5.5.2 Facilities to obtain good balance with flexibility to have dimming
on any circuit.
5.5.3 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.
5.6 DIMMERS
Three basic methods for dimming are :5.6.1 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.
5.6.2 Saturable Reactor (System SR)
The basic principle of the saturable reactor is to connect an iron cored choke in series
with the lamp.

14

5.7 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.
In colour, to obtain a night effect, blue cinemoid is used over the luminaries. This
gives a stylized effect. An alternative is to use much more localized lighting than for
daylight and light only the artists and odd parts of the set.

15

CHAPTER 6
MICROPHONES

Fig 6.1 Microphone

6.1 INTRODUCTION
Microphone plays a very important role in the art of sound broadcasting. It is a device which converts acoustical energy into electrical energy. In the professional
broadcasting field microphones have primarily to be capable of giving the highest
fidality of reproduction over audio bandwidth.
6.2 MICROPHONE CLASSIFICATION
Depending on the relationship between the output voltage from a microphone and the
sound pressure on it, the microphones can be divided into two basic groups.



Pressure Operated Type.
Velocity or Pressure Gradiant Type

6.3 TYPES OF MICROPHONES
There are many types of microphones. But only the most common types used in
broadcasting have been described here:
.
6.3.1 Dynamic Or Moving Coil Microphone
6.3.2 Ribbon/ Velocity Microphone
6.3.3 Electrostatic or Condenser Microphone
6.3.4 Electret ‘Microphone

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CHAPTER 7
RECORDING
7.1 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:

Principles of video tape

Fig 7.1 Magnetic Principle
7.2 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.

CHAPTER 8
DIGITAL VIDEO CASSETTE RECORDING
PROFESSIONAL
(DVCPRO)
8.1 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.
8.2 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 DCT compression using 4:1:1 chroma subsampling for NTSC (or 4:2:0 for
PAL).

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CHAPTER 9
VISION MIXING
9.1 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.
9.2 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.
9.3 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.
9.4 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 itself.

19

CHAPTER 10
TELEVISION TRANSMISSION
10.1 VESTIGIAL SIDE BAND TRANSMISSIONIf 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

.
Fig 10.1
10.2 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.
10.3 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.

Fig 10.2 Block Diagram Of TV Exciter (Mark-11)
20

10.4 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 amplification is used in HPTs though combined amplification requires fewer amplifier stages.
10.5 IF MODULATION
It has following advantages
 Ease of correcting distortions
 Ease in Vestigial side band shaping
 IF modulation is available easily and economically
10.6 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 15000CX) are used in vision transmitter chain.
Aural transmitter chain is fully solid state in Mark III transmitter.
10.7 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.

10.8 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

Functions performed by MCS (Main Control System)- XTR control -Interlocking.
21

- RF monitoring
- Supporting operation from control console
- Three second logic for protection against sudden fluctuation.
- Thermal protection for 1 kW and 10 k 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).

22

CHAPTER 11
OUTDOOR BROADCASTING VAN
OB van is used for live broadcasting like any match or any event. It consist all the
equipment’s 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

Fig 11.1 Inner View Of OB Van

Fig 11.2 Inner Structure of OB van

23

CHAPTER 12
EARTH STATION
12.1 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 INSAT : Indian Satellites
AUSSAT : Australian Satellites
BRAZILSAT : Brazilian Satellites
FRENCH TELECOM : French Satellites
ITALSAT : Italian Satellites
CHINASAT : Chinese Satellites
STATSIONAR, GORIZONT, Russian Satellites
12.2 ARCHITECTURE OF A SATELLITE COMMUNICATION SYSTEM
12.2.1 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 uplink. 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.
24

Fig 12.1 Satellite Communication System

25

12.2.2 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.
12.3 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 .
12.4 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.
12.5 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.

26

12.6 CIRCULAR 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).
12.7 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.

27

CHAPTER 13
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)

Fig 13.1 Satellite Earth Station Uplink / Downlink Chain

13.1 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 up
conversion (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.
13.2 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.
13.3 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
13.4 AZIMUTH AND ELEVATION
For receiving a satisfactory signal from the satellite the dish antenna should be pointed towards the satellite accurately. For that we need to know the azimuth and ele28

vation of a particular satellite from our place. The azimuth and elevation are angles
which specify the direction of a satellite from a point on the earth's surface. In layman
terms the azimuth is the east west movement and the elevation can be defined as the
north south movement of the dish.

Both the azimuth and elevation of a dish can be affected by three factors for geostationary satellites.
They are
1. The longitude of the satellite.
2. The latitude of the place.
3. The longitude of the place.
Calculation of Azimuth

13.5 INDOOR UNITS
The indoor unit contains two units. They are :
13.5.1 System unit
13.5.2 Satellite Receiver Unit
13.6 SYSTEM UNIT
The system unit contains a passive power divider and power supply for the LNBC.
The power divider divides the IF into two equal parts to be applied to the two receivers. The power supply is fed through same cable to the LNBC. Satellite Receiver
Unit The satellite receiver contains the down converter, video/audio demodulators and
processing circuits. Finally we get two video/audio outputs. A synthesized receiver
accepts signal in the range of 900 to 1700 MHz. The block diagram of a typical EC
receiver is shown in figure 9. The IF is applied to a four-stage low noise amplifier for
amplification. The overall gain of the amplifier is around 22 dB. This signal is then
applied to FET mixer where a LO frequency of 1500 to 2300 MHz is mixed so that
an IF of 600 MHz is produced. The local oscillator consists of two similar VCOs
(voltage controlled oscillator) one operating in the range of 1500 - 1749 MHz and the
other in the range of 1750 to 2300 MHz. They are controlled by a synthesizer IC. A
sample of the LO frequency is taken and phase compared with a stable reference crystal frequency of 4 MHz and error if any, is then applied to the VCO for frequency correction through a low pass filter. Thus the VCO works in a phase locked loop mode.

29

CHAPTER 14
DIRECT-TO-HOME SATELLITE BROADCASTING (DTH)
14.1 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 equipment’s 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 (Dia60 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.

14.2 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 50Watts) 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).
30

Fig 14.1 DTH to UPLINK Setup

Fig.1 shows schematic of uplink chain proposed to broadcast bouquet of 30 video
programs in Doordarshan, Prasar Bharati, India. 30 video programs may 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)
14.3 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

31

CONCLUSION
Doordarshan is the oldest and the biggest Broadcasting media in India.
In my training session I learned a lot. Not only in technical field but also in social field
too. I got a great experience of working in a Public Sector Company.
I learned about the recent trends in Broadcasting Media and also the market strategies to
maximize the profit using limited resources.

32

REFERENCES
1.
2.
3.
4.

Monochrome and Colour television by R R Gulati
www.ddlucknow.com
www.ddinews.gov.in
www.scribd.com

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