The document is a project report on the television system. It discusses fundamentals of monochrome and color TV systems including picture formation, number of TV lines per frame, resolution, brightness, contrast, and color composite video signals. It also covers color television topics such as additive color mixing, color difference signals, bandwidth requirements, color carrier modulation, and chroma vectors. Finally, it discusses the PAL color encoding system, audio video chains in TV stations, and DTH broadcasting including downlink and uplink chains.

1. project report
ON
THE TELEVISION SYSTEM
Staff Training Institute (technical)
Lucknow
Ishank Ranjan
5th Sem
B.Tech(EEE)
H.C.S.T. Mathura

2. Acknowledgement
This report is an outcome of the contributions made by some
of the peoples. Therefore it is my sole responsibility to
acknowledge them. I am greatly thankful to the sincere
efforts made by Mr. Ravindra Naithani without whom this
project would be abstract. I also thank the staff of DDK, Lko
(Doordarshan Kendra ,Lucknow) who took out there precious
time to tell me about the various equipments. My special
thanks is dedicated to Mr. K. S. Chauhan (Assistant
Engineer, Doordarshan Kendre -Leh).
I would also mention the outstanding support given by my
parents who paved the way for me to overcome with this
project report.
ISHANK RANJAN
B.Tech (5th Sem)
Electrical & Electronics Engineering
Hindustan College Of Science And Technology
Mathura.

3. Certificate
This is to certify that ISHANK RANJAN, a student of
Hindustan College Of Science And Technology pursuing
B.tech in Electrical & Electronics Engineering branch has
undergone industrial training in Doordarshan Kendra Lucknow
from 4th of July,2012 to 28th of July,2012. And this project
report is based on it.
Dated- (Signature)
Mr. R. Naithani
Training coordinator
Doordarshan Kendra ,Lucknow

4. Contents
PART (1) Fundamentals Of Monochrome And Colour Tv System
a) Picture Formation
b) Number Of TV Lines Per Frame
c) Resolution
d) Brightness
e) Contrast
f) Colour Composite Video Signal (CCVS)
PART (2) The Colour Television
a) Introduction
b) Additive Colour Mixing
c) Colour Difference Signals
d) Band Width Requirement
e) Colour Carrier And Modulation Of R-Y And B-Y Signals
f) Croma Vector
PART (3) The PAL System
a) Introduction
b) Pal Encoder
c) Pal Decoder
PART (4) Audio Video Chain In a TV Statio
a) Introduction
b) Studio Center
c) Action Area
d) Production Control Area
e) Central Apparatus Room(CAR)
f) Sync Pulse-Generator(SPG)
g) Camera Control Unit (CCU)
PART (5) DTH Broadcasting
a) Introduction
b) Down-Link Chain
c) Uplink Chain

5. Dedicated
To
My Parents
Mrs. Ranjana Srivastava
&
Mr. R.C. Srivastava

6. 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 pickup 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 (Field rate is the same as power supply
frequency).
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7. • 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.
A compromise between quality and conservation of r.f. spectrum led to
the selection of 625 lines in CCIR system B. Odd number is preferred for
ease of sync pulse generator (SPG) circuitary to enable interlace of
fields.
• Resolution
The scanning spot (beam) scans from left to right. The beam starts at
the left hand edge of the screen and goes to right hand edge in a
slightly slanty way as the beam is progressively pulled down due to
vertical deflection of beam (as top to bottom scanning is to take place
simultaneously). When the beam reach the right hand edge of the
screen the direction of beam is reversed and goes at a faster rate to the
left hand edge (below the line scanned). Once again the beam direction
is reversed and scanning of next line starts. This goes on till the beam
completes scanning 312 and half lines reaching the bottom of the
screen. At this moment the beam flies back to top and starts scanning
starting from half line to complete the next 312 and half lines of the
frame.
To avoid distortions in the picture whenever the beam changes its
direction, it is blanked out for a certain duration.
The horizontal blanking period is 12 microseconds. Since each line takes
64 micro seconds the active period of line is 64 -12 = 52 micro seconds.
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8. (Since 625 lines are scanned at the rate of 25 Hz i.e. 25 cycles per
second, the number of lines scanned in one second is 625 multiplied by
25 which yields 15,625. So the horizontal frequency is 15,625 hertz and
hence each line takes 64 micro seconds).
Similarly there is vertical blanking period and 25 TV lines are blanked
out during the period. So in one frame 50 TV lines are blanked out.
Hence effective lines are 625 minus 50 i.e. 575.
The vertical resolution depends on the number of scanning lines and
the resolution factor (also known as Kell factor). Assuming a reasonable
value of Kell factor as 0.69. The vertical resolution is 575 multiplied by
0.69 which gives nearly 400 lines.
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. Let us also take another factor. It is realistic to aim at equal vertical
and horizontal resolution. We have seen earlier that the vertical
resolution is limited by the number of active lines. We have already
seen that the number of active lines are 575. so for getting the same
resolution in both vertical and horizontal directions the number of
alternate black and white elements on a line can be 575 multiplied by
Kell factor and aspect ratio. Therefore, the number of alternate black
and white dots on line can be 575 x 0.69 x 4/3 which is equal to 528.
• 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).
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9. In black and white TV the concept of gray scale is adopted for
costumes, scenery etc. If the foreground and back ground are identical
in gray scale, they may merge and the separation may not be noticed
clearly on the screen.
• 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.
• Colour Composite Video Signal (CCVS)
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.
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10. It consists of:-
i. Video signal along with synchronizing singal,composed of line and
field synchronizing pulses to ensures the locking of scanning
systems of a source and destination.
ii. Blanking pulses to blank retrace period around the horizontal and
vertical synchronizing periods.
iii. Sub carrier and its modulated components to carry the colour
information.
iv. Burst gate signal (responsible for correct positioning of colour
burst).
Page 5 of 36

11. The Colour Television
Introduction
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).
Fig. Approximate relative sensitivity of the average human eye to
different wave lengths
Page 6 of 36

12. • Additive Colour Mixing
The figure 10 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. Additive Colour Mixing
It is possible to obtain any desired colour by mixing three primary
colours i.e., red, blue and green in suitable proportion. Thus it is only
required to convert optical information of these three colours to
electrical signals and transmit it on different carriers to be decoded by
the receiver. This can then be converted back to the optical image at
the picture tube. The phosphors for all the three colours i.e. R, G and B
are easily available to the manufacturers of the picture tube. So the
pick up from the cameras and output for the picture tube should
consists of three signals i.e. R, G and B. It is only in between the camera
Page 7 of 36

13. and the picture tube of the receiver we need a system to transmit this
information.
Fig. Colour Tv System
Colour television has the constraint of compatibility and reverse
compatibility with the monochrome television system which makes it
slightly complicated. Compatibility means that when colour TV signal is
radiated the monochrome TV sets should also display Black & White
pictures. This is achieved by sending Y as monochrome information
along with the chroma signal. Y is obtained by mixing R, G & B as per
the well-known equation:
Y = 0.3 R + 0.59 G + 0.11 B
Reverse compatibility means that when Black & White TV signal is
radiated the colour TV sets should display the Black & White pictures.
In view of the above the colour TV system should have:
a) Same line and field standards as that of existing monochrome.
b) The same bandwidth as that of the existing monochrome system.
c) The monochrome information in the Luminance signal along with
colour signal.
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14. If we transmit R, G, B, the reverse compatibility cannot be achieved. Let
us see how :
If we transmit Y, R & B and derive G then :
Since,
Y = 0.3R + 0.59G + 0.11 B
G = 1.7Y - 0.51 R - 0.19 B
In such a case what happens with a colour TV set when we transmit
black and white signal. R and B are zero, but G gun gets 1.7 Y. The net
result is black & white pictures on a colour TV screen appear as Green
pictures. So reverse compatibility is not achieved.
• Colour Difference Signals
To achieve reverse compatibility, when we transmit Y, R-Y and B-Y
instead of Y, R & B, we do not take G-Y as this will always be much
lower than R-Y and B-Y and hence will needs more amplification and
will cause more noise into the system. G-Y can be derived electronically
in the TV receiver.
In the previous paragraph we have seen
G = 1.7 Y - 0.51 R - 0.19 B
So G-Y = -0.51 (R-Y) - 0.19 (B-Y)
Thus, colour difference signals fulfill the compatibility and reverse
compatibility. Because in this case the colour difference signals are zero
if the original signal is monochrome (i.e. R = B = G)
So if we take R – Y
R - Y = R - (0.3 R + 0.59 R + 0.11 R) = 0
Similarly , B-Y=0
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15. As such colour difference signals are zero for white or any shade of gray
whereas, Y carries the entire Luminance information.
It is to be noted while R, G, B signals always have positive value R-Y,
B-Y and G-Y signals can either be positive or negative or even zero.
• Band Width Requirement
We have already seen that compatibility calls for utilizing the same
bandwidth as that of existing monochrome. In the system we are
following it is 5 Megahertz for Video. Restricting the bandwidth of
Luminance results in poor resolution. Then how to share the same 5
megahertz bandwidth between Y and the colour difference signals R-Y
and B-Y. A way is to be found to accommodate the colour difference
signal within the Luminance bandwidth WITHOUT CAUSING ANY
SIGNIFICANT INTERFERENCE. Also Luminance signal is to be
transmitted in the same way as that monochrome receiver can receive
it. Hence a method of inter leaving is to be adopted to suit
compatibility.
• Colour Carrier And Modulation of R-Y And B-Y
Signals
Spectral analysis of luminance Signal shows that various frequency
components occur at multiples of line (H frequency) due to the periodic
scanning. The space between the two energy contents is utilized to
accommodate Chrominance signal within Luminance Signal.
Assume an oscillator output is connected to the TV picture tube input.
Severe patterns appear on the screen. When the Oscillator frequency is
a multiple of TV line frequency (H frequency) the patterns become
stable. As the oscillator frequency rises through the Luminance band
the pattern becomes finer eventually becoming a series of dots. If the
oscillator frequency is an odd multiple of Line frequency then the dots
Page 10 of 36

16. pattern of one field lies exactly between the dots produced two fields
later. Persistence of vision will cause dot pattern to go to a minimum.
minimu
This has led to the selection of a carrier frequency that gets modulated
by the colour difference signal which is close to the edge of bandwidth
on the high frequency side.
Fig. Energy Spectrum Of TV Signal
As we know the video spectrum is occupied only at multiples of Line
frequency and in their vicinity. The spectrum exhibits gaps in between
these frequency groups. So if the chrominance spectrum is placed in
these gaps the interference will be negligible. That means the sub
carrier frequency should be an odd multiple of half-line frequency.
line
From the above it is clear that sub carrier frequency should be near to
the upper edge of video bandwidth (i.e. as high as possible) and also
should be an odd multiple of half
half-line frequency.
Page 11 of 36

17. This sub-carrier gets modulated by colour difference signals R - Y and
B - Y to produce Chrominance that gets interleaved with Luminance
signal.
• Croma Vector
Luckily the requirement of bandwidth of chrominance signal is less. This
is because of the capacity of human eye. The capacity of human eye to
distinguish between hues depends on the size of the objects, the
lighting condition and the distance. In a very badly lit room you cannot
distinguish the colour of the objects if they are small in size and are at a
distance. However, you can notice the objects by their Luminance
value. It means they give rise to Luminance signal but not chrominance
signal.
Even in good lighting condition we cannot notice hue till we go near the
objects. However their brightness value is first noticed as we go near
and when go still nearer we see colour. This only shows that the
bandwidth requirement of chrominance signal is much. In the PAL
system the chrominance bandwidth is restricted to 1.3 MHz. The sub-
carrier frequency is 4.43 MHz.
Though carrier is single we need two carriers for R - Y and B - Y to
modulate independently. How do we get two carriers? In fact both are
of the same frequency but are displaced in phase by 90 degrees. Hence
we speak of quadrature modulation of sub-carrier frequency by the
colour difference signals. The type of modulation used is Amplitude
Modulation. One carrier is amplitude modulated with R - Y and the
other with B - Y and in both cases the carrier is suppressed. The two
modulated signals at 90 degrees to each other produce the resultant
chrominance signal which gets added to Luminance signal to form
Composite colour Video Signal (CCVS).
Page 12 of 36

18. Fig. Generation Of Croma Vector
The R-Y and B - Y chrominance signals may be recovered at the
television receiver by suitable synchronous demodulation. But sub sub-
carrier is to be generated by a local oscillator. This generated subsub-
carrier in the receiver must have same frequency as that of transmitted
sub-carrier and also the same phase. This is achieved by transmitting 10
carrier
cycles of sub-carrier frequency on the back porch of H synchronizing
carrier
pulse. This 10 cycles sub-carrier signal is known as BURST or colour
sub carrier
BURST. One line display is shown below:-
Page 13 of 36

19. The PAL System
(Phase Alteration By Line)
You may note that in view of the phase alternation line by line, a given
hue will be represented on a vector diagram at two alternating
positions symmetrically displaced above and below B-Y axis in alternate
BY
lines. You might have noticed two colour vectors for each colours on a
vector scope display because of this reason.
Fig. Colour bar Display On Vectroscope
In the case of PAL's Receiver the ability of eyes to combine the hues on
the adjacent lines is utilised. However the resultant picture is less
es
satisfactory for phase errors exceeding 15 degrees.
Fig. PAL-D Receiver
Page 14 of 36

20. • PAL Encoder
The design of PAL Encoder may vary from manufacturer to
manufacturer. In some of the PAL encoder instead of reversing the
phase of V component on every alternating line, it has been found
much easier to change the phase of carrier modulating the R-Y
component by 180 degree every alternate line. This switching is
controlled by the H/2 oscillator i.e., by a 7.80 kHz PAL Indent pulse.
(H/2 because of alternate line phase reversal). In order to facilitate TV
receiver to decode which line has +V component and which line has -V
component we send additional information by modifying the burst.
Burst preceding a line carry this information. This is achieved by
changing its phase. It is 135 and 225 degrees for +V & -V respectively. It
is also known as swinging burst.
The block diagram of PAL encoder explains a system having the
following steps:-
1) Add R G B to generate Y, R-Y & B-Y
2) Modulate R-Y by SC at 90o for line n and 270 o for line n+1.
Switching of SC phase is controlled by 7.80 kHz, switching
pulse.
3) Modulate B-Y by SC at 0o phase.
4) To generate SC with V switching information i.e. either at
135/225o (burst) each alternate line. (Swinging burst)
5) Generation of pulse called PAL-indent signal of 7.80 kHz.
6) Generating of burst gate or K pulse to define the parking
space for burst at the back porch.
7) Adding of 2, 3, 4, Y and sync to generate CCVS i.e., colour
composite Video signal as Encoder output.
Page 15 of 36

21. Also the burst preceding the line indicates whether the V component
is +ve or -ve, and it contains equal component of U and V.
ve,
Fig. Block Diagram Of PAL Encoder
Fig. PAL Encoder Angle System
Page 16 of 36

22. • PAL Decoder
PAL decoder is a reverse of encoding process. The objectives of
recovering R G & B from the received signal is achieved in the following
steps:
1) Y & S is recovered by decoding video & using LPF and Sync
separator circuit of receiver.
2) Chroma is separated by using BPF (center at 4.43 MHz)
3) Chrome is keyed or gated to get back the burst i.e. SC by using
K - Pulse.
4) L.O. 4.43 MHz is phase locked with the recovered burst to
make it of same phase as that of the transmitted one.
5) 4.43 MHz SC is processed further to get the same pulse at 90
degree phase as well.
6) Modulated chroma is demodulated by these two SC at 0 & 90
degree. This will retrieve U & V components.
7) Phase of the V component is restored back to normal by using
the concerned information from the transmitted burst.
8) U & V are demodulated back to R-Y & B-Y.
9) Y, R-Y & B-Y are mixed to retrieve R G B which will control the
three grids of picture tube.
Page 17 of 36

23. Fig. Block Diagram Of PAL Decoder
Page 18 of 36

24. AUDIO VIDEO CHAIN IN A TV STATION
• Introduction:
Studio centers of Doordarshan kendras are required to generate
programmes. The delivery of these programes to the viewers is either
done by satellite or terrestrial mode. As a satellite channel the
programs have larger reach across the entire country. Sate
Satellite channels
are radiated from the respected Earth Station
In a terrestrial Mode, the programes are having a limited range in a city.
These programes are radiated by TV transmitter as an RF signal and
received by TV receiver by using TV antenna.
antenna
Page 19 of 36

25. • STUDIO CENTER
A Studio center of Doordarshan has the following objectives:
1) To originate programmes from studios either for live telecast or
for recording on a video tape.
2) To knit various other sources of programs available at the
production desk i.e., camera output from studios, feed from other
kendras, outdoor, playback from prerecorded tape, film based
programs slides, video graphics and characters generator etc. This
knitting or live editing includes generation of special effects and
desired transitions between various sources.
3) Processing/distribution of different sources to various
destinations in technical areas.
4) Routing of mixed programme for recording/transmission via
master switching room and Micro Wave to the transmitter or any
other desired destinations.
Activities in a television studio can be divided into three major areas
such as :
1) Action area,
2) Production control room, and
3) Central apparatus room,
Action area
This place requires large space and ceiling as compared to any other
technical area. Action in this area includes staging, lighting,
performance by artists, and arrangement to pick up picture and sound.
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26. Hardware required for these activities in a studio (typical size 20
x20x8.5 cubic meters) are:
i. Very efficient air conditioning because of lot of heat dissipation by
studio light and presence of large number of persons including
invited audience performing artists and operational crew.
ii. Uniform and even flooring for smooth operation of camera dollies
and boom microphone etc.
iii. Acoustic treatment keeping in mind that a television studio is a
multipurpose studio with lot of moving person and equipment
during a production.
iv. Supporting facilities like properties, wardrobe, and makeup etc.
v. Effective communication facilities for the floor crew with the
production control area.
vi. Studio cameras (three to four) with one of the cameras fitted with
teleprompter system and pressure dolly.
vii. Luminaires and suspension system having grids or battens
(hand/motorised operation).
viii. Pick up wall sockets for audio operations.
ix. Tie lines box for video and audio lines from control room.
x. Cyclorama and curtain tracks for blue and black curtain for
chroma keying and limbo lighting respectively.
xi. Audio and video monitoring facilities.
xii. Studio warning light and safety devices like fire alarm system and
firefighting equipment etc.
xiii. Digital clock display.
Page 21 of 36

27. Fig. Use of synchronizing signals to generate Colour Composite Video
Signal (CCVS)
Production control area
Activities in this area are:-
i. Direction to the production crew by the producer of the
programme.
ii. Timing a production/telecast.
iii. Editing of different sources available at the production desk.
iv. Monitoring of output/off air signal.
Hardware provided in this area include:
1. Monitoring facilities for all the input and output
sources(audio/video).
2. Remote control for video mixer, telecine and library store and
special effect (ADO) etc.
3. Communication facilities with technical areas and studio floor.
Page 22 of 36

28. Vision mixing and switching
Unlike films, television media allows switching between different
sources simultaneously at the video switcher in Production control
room operated by the Vision Mixer on the direction of the program
producer. The producer directs the cameramen for proper shots on
various cameras through intercom and the vision mixer (also called VM
engineer) switches shots from the selected camera/cameras with split
second accuracy, in close cooperation with the producer. The shots can
be switched from one video source to another video source,
superimposed, cross faded, faded in or faded out electronically with
actual switching being done during the vertical intervals between the
picture frames. Electronics special effects are also used now days as a
transition between the two sources.
For most of the Video Switcher Mixing between the sources is possible
only if the sources are having timing accuracy between 50 ns to 200 ns
and Burst phase for SC with an accuracy of 1.5 to 5 deg.
Though the video switching is done by the VM at the remote panel, the
electronics is located in CAR. The vision mixer is typically a 10 x 6 or 20 x
10 cross bar switcher selecting anyone of the 10 or 20 input sources to
6 or 10 different output lines. The input sources include: Camera 1,
camera 2, camera 3, VTR1, VTR2, Telecine 1, Telecine 2, Test signal etc.
Some of the sources that have their sync coincident with the station
sync are called synchronous, while others having their own
independent sync are called non-synchronous.
Page 23 of 36

29. The vision mixer provides for the following operational facilities for
editing of TV programs:-
a. Take: Selection of any input source or Cut: switching clearly from
one source to another.
b. DISSOLVE: Fading out of one source of video and fading in
another source of video.
c. SUPERPOSITION OF TWO SOURCES: Keyed caption when selected
inlay is superimposed on the background picture.
d. SPECIAL EFFECTS: A choice of a number of wipe patterns for split
screen or wipe effects.
The selected output can be monitored in the corresponding pre-view
monitor. All the picture sources are available on the monitors. The
preview monitors can be used for previewing the telecine, VTR; test
signals etc. with any desired special effect, prior to its actual
switching.
The switcher also provides cue facilities to switch camera tally lights as
an indication to the cameraman whether his camera is on output of the
switcher.
Character Generator(CG)
Character Generator provides titles and credit captions during
production in Roman script. It provides high resolution characters,
different colours for colorizing characters, background, edges etc. At
present bilingual and trilingual C.G are also being used by Doordarshan.
Character Generator is a microcomputer with Texts along instructions
when typed in at the keyboard is stored on a floppy or a Hard disk.
Many pages of scripts can be stored on the disk and recalled when
Page 24 of 36

30. needed, by typing the addresses for the stored pages, to appear as one
of the video sources.
Central Apparatus Room(CAR)
This is the nerve center for a television station. Activities in this area
include:
1) Distribution of stabilised power supply to different technical areas
with protection devices.
2) Sync pulse generation and distribution.
3) Distribution of sources to various destinations
4) Video processing and routing.
5) Electronics for camera chain, video switchers, special effect
generator, and test signal and pattern generator.
6) Monitoring facilities
7) Patch panel for video and audio lines
8) Electronics for micro wave links
Sync Pulse-Generator(SPG)
It is essential that all the video sources as input to the switcher are in
synchronism i.e., start and end of each line or all the frames of video
sources is concurrent. This requirement is ensured by the sync pulse
generator (SPG). SPG consists of highly stable crystal oscillator. Various
pulses of standard width and frequency are derived from this crystal
electronically which form clock for the generation of video signal. These
pulses are fed to all the video generating equipment to achieve this
objective of synchronism. Because of its importance, SPG is normally
duplicated for change over in case of failure.
It provides the following outputs:
Page 25 of 36

31. • Line drive
• Field drive
• Mixed blanking
• Mixed sync
• colour subcarrier
• A burst insertion pulse
• PAL phase Indent pulses
Fig. Typical Studio Timing Arrangement
Camera Control Unit (CCU)
The television cameras which include camera head with its optical
focusing lens, pan and tilt head, video signal pre-amplifier view finder
pre amplifier
and other associated electronic circuitry are mounted on cameras
trolleys and operate inside the studios. The output of cameras is pre-
pre
amplified in the head and then connected to the camera control unit
(CCU) through long triax cable. All the camera control voltages are fed
from the CCU to the camera head over the Triax cable. The view
view-finder
signal is also sent over the camera cable to the camera head view- view
Page 26 of 36

32. finder for helping the cameraman in proper focusing, adjusting and
composing the shots.
The video signal so obtained is amplified, H.F. corrected, equalized for
cable delays, D.C. clamped, horizontal, and vertical blanking pulses are
added to it. The peak white level is also clipped to avoid overloading of
the following stages and avoiding over modulation in the transmitter.
The composite sync signals are then added and these video signals are
fed to a distribution amplifier, which normally gives multiple outputs
for monitoring etc.
• Light Control
The scene to be televised must be well illuminated to produce a clear
and noise free picture. The lighting should also give the depth, the
correct contrast and artistic display of various shades without multiple
shadows.
The lighting arrangements in a TV studio have to be very elaborate. A
large number of lights are used to meet the needs of „key‟, „fill‟, and
„back‟ lights etc. Lights are classified as spot and soft lights. These are
suspended from motorized hoists and telescopes. The up and down
movement is remotely controlled. The switching on and off the lights at
the required time and their dimming is controlled from the light control
panel inside a lighting control room using SCR dimmer controls. These
remotely control various lights are inside the studios.
Modern TV studios have a computer-controlled lighting system. The
intensities of various lights can be adjusted independently and
memorised for reproduction. The status indication of lights regarding
their location and intensity is available on a monitor/MIMIC display.
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33. During reproduction of a particular sequence, the information from the
memory operates the respective light dimmers. Hand held control
boxes are also available for controlling light intensities inside the
studios which communicate via a control panel. Most of the operational
controls of the computerised light control system can also be
performed manually with the back –up matrix and fader controls.
• Sound mixing and control
As a rule, in television, sound accompanies the picture. Several
microphones are generally required for production of complex
television programs besides other audio sources also called marred
sound from telecine, VTR, and audio tape/disc replays. All these audio
sources are connected to the sound control console.
The sounds from different sources are controlled and mixed in
accordance with the requirement of the program. Split second accuracy
is required for providing the correct audio source in synchronisation
with the picture thus requiring lot of skill from the engineer. Even the
level of sound sometimes is varied in accordance with the shot
composition called prospective.
• Audio facilities
An audio mixing console, with a number of inputs, say about 32 inputs
is provided in major studio. This includes special facilities such as
equalisation, PFL, phase reversal, echo send/receive and digital
reverberation units at some places Meltron console tape recorders and
EMI 938 disc reproducers are provided for playing back/creating audio
effects as independent sources (Unmarried) to the switcher.
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34. • Video Tape recorders
VTR room is provided at each studio center. It houses a few Broadcast
standard Videocassette recorders (VCRs). In these recorders, sound and
video signals are recorded simultaneously on the same tape.
• Post Production Suites
Modern videotape editing has revolutionised the production of
television programs over the years. The latest trend all over the world is
to have more of fully equipped post production suites than number of
studios. Most of the present day shootings are done on locations using
single camera. The actual production is done in these suites. The job for
post-production suites is:-
1. To knit program available on various sources.
2. While doing editing with multiple sources, it should be possible to
have any kind of transition.
3. Adding/Mixing sound tracks.
4. Voice over facilities.
5. Creating special effects.
The concept of live editing on vision mixer is being replaced by “to do it
at leisure” in post production suites.
A well equipped post production suite will have four NLE & 3-D graphics
machines and Betacam SP or DVC Pro Recorders.
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35. Coverage of Outside events
Outside broadcasts(or OBs) provide an important part of the television
programs. Major events like sports, important functions and
performances are covered with an O.B. van which contains all the
essential production facilities.
• Video Chain
The block diagram on facing page connects all these sections and it can
be observed that the CAR is the nodal area. Now let us follow a CAM-I
signal. CAM-I first goes to a Camera electronics in CAR via a multi-core
cable, the signal is then matched/adjusted for quality in CCU and then
like any other sources it goes to video switcher via PP (Patch Panel) and
respective VDAs(Video Distribution Amplifiers) and optional Hum
compensator/Cable equalizers.
Output from the switcher goes to stabilizing amplifier via PP and VDAs.
Output from the stab. Is further distributed to various destinations. It
may be noted that the use of VDAs helps to monitor the video signal at
different locations and the use of PP is very helpful for emergency
arrangements during breakdowns and trouble shooting. A separate
monitoring bus is provided in CCU, LCU and END CONTROL with sources
as shown.
END CONTROL also has a remote for the adjustment of levels etc. in the
STAB AMP unit. Route for the other sources is similar to this and can be
understood from the block schematic.
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36. DTH Broadcasting
(Direct To Home)
• 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
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37. 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
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38. 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).
Figure 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). Groups A, B and C are up-
converted to Ku-Band frequencies, (=13778 MHz), (=13891 MHz) and
(=13973 MHz), respectively and are individually amplified through
Klystron High Power Amplifiers (KHPA). The three RF signals are
combined in RF combiner and then finally fed to 6.2m dish antenna
for up-linking.
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39. Fig. DTH Uplinking Setup
• DOWN-LINK CHAIN
LINK
Down-Link or receiving chain of DTH signal is depicted in Fig.2. There
Link
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
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40. electrical signal is amplified and further down converted to L-Band
L
(950-1450) signal. Feed and LNBC are now combined in single unit
1450)
called LNBF. The L- -Band signal goes to indoor unit, consisting a set
oor set-
top box and television through coaxial cable. The set-top box or
set
Integrated Receiver Decoder (IRD) down converts the L L-Band first IF
signal to 70 MHz second IF signal, perform digital demodulation, de- de
multiplexing, decoding and finally gives audio/video output to TV for
finally
viewing.
Fig. Receiving Chain of DTH signal
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41. Conclusion
Now I have studied a lot about the television. One must have never
thought that so many things are required for watching a television.
The camera, the studio, the transmitter, the PDA, the setup box
(installed in houses) everything is connected to each other. Here
man and electronics work as if they are a family. So many process
and lots of hard work, sincerity is required to just have a show or say
a movie on air i.e. to be broadcasted. So many people are involved in
it. I really enjoyed of being part of it. The saying is really true that…
“Tell me ,I may forget
Teach me, I may remember
But involve me, and I have learn it”
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