Doordarshan “DOORDARSHAN” Industrial Training Report Submitted in the partial fulfillment of requirement for the award of degree ofBachelor of Engineering In Electronics and Communication Engineering Submitted By Rachit Sharma (En. No 291 /07) Submitted to M/s.Arpanjee t Kour Lect. ECE Deptt. Department of Electronics And Communication Engineering MAHANT BACHITTAR SINGH COLLEGE OF ENGINEERING &TECHNOLOGY JAMMU. (J&K) 2010 M.B.S College of Engineering. and Technology 1
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material. In recent years Internet television has seen the rise of television available via the
Internet, eg iPlayer and Hulu.
1.1 HISTORY
In its early stages of development, television employed a combination of optical, mechanical
and electronic technologies to capture, transmit and display a visual image. By the late 1920s,
however, those employing only optical and electronic technologies were being explored. All
modern television systems rely on the latter, although the knowledge gained from the work
on electromechanical systems was crucial in the development of fully electronic television.
The first images transmitted electrically were sent by early mechanical fax machines,
including the pantelegraph, developed in the late nineteenth century. The concept of
electrically powered transmission of television images in motion was first sketched in 1878
as the telephonoscope, shortly after the invention of the telephone. At the time, it was
imagined by early science fiction authors, that someday that light could be transmitted over
wires, as sounds were.
The idea of using scanning to transmit images was put to actual practical use in 1881 in the
pantelegraph, through the use of a pendulum-based scanning mechanism. From this period
forward, scanning in one form or another has been used in nearly every image transmission
technology to date, including television. This is the concept of "rasterization", the process of
converting a visual image into a stream of electrical pulses.
In 1884 Paul Gottlieb Nipkow, a 23-year-old university student in Germany, patented the first
electromechanical television system which employed a scanning disk , a spinning disk with a
series of holes spiraling toward the center, for rasterization. The holes were spaced at equal
angular intervals such that in a single rotation the disk would allow light to pass through each
hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an
image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole
image.
Nipkow's design would not be practical until advances in amplifier tube technology became
available. The device was only useful for transmitting still "halftone" images—represented by
equally spaced dots of varying size—over telegraph or telephone lines. Later designs would
use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a
display device, but moving images were still not possible, due to the poor sensitivity of theselenium sensors. In 1907 Russian scientist Boris Rosing became the first inventor to use a
The programmer control room is one of the essential blocks of DDK. It can be termed asrecording Centre for the programmer. The live telecast of the programmer such as news,
interviews etc. also take place here. This is one among the major sections of DDK and
involves a number of technical and non- technical persons. Recording takes place according
to a predetermined schedule called programed schedule. The PCR of DDK Jammu is double
storied building having in it three studios and their control rooms. It lies just opposite to
Administration and has constructed 30 years ago.
The PCR consists of following three sections:
1. Studio.
2. Video Tape Recorder.
3. Audio Section.
2.1 STUDIO (CAMERA SECTION)
Studio is the room where a program is performed and recorded using cameras. The studio
number of these lights may reach 50 in order to cover the whole of the studio usually the no.
of cameras used is three. A typical camera is shown on the following page. Various set are
made. The selection of particular set depends on the type of program that cameras are
assigned the numbers i.e. camera 1, camera 2 etc. The position of camera is so adjusted that
we get different views from each camera. It is he who adjusts the settings of the camera and
people who perform as per the instructions of the program producer instructions to start,
silent atmosphere is created and every body prepares for the final go. The video signal sent to
It stands for videotape recorder. VTR is an essential section of PCR. This is in fact the main
recording room having co-ordination with both the studio as well as Audio section. Thissection is controlled by producer and his assistant. Here the output of all the cameras is
characteristics, requires less multiple stages. It has excellent distortion factor and AF
characteristics
7. Cooling is maintained using blowers. This can be led via floor surface or top of the
transmitter.
8. The devices have protective relays and are also protected by an inter lock circuit
which s the transmitter to be started only according to a predetermined sequence
3.3 FORWARD ERROR CORRECTION
It is only applicable for digital transmissions. The FEC (Forward Error Correction) indicates
how are used for the actual signal, and how many for correction of errors. A FEC of 1 Byte
out of 2 is used for error correction, while a ratio of 7/8 means 7 Bytes are used for actualsignal, and only one for error correction. A FEC of 1/2 gives as perfect as reception, since
every Byte containing actual signal is controlled by another Byte en a provider chooses a
FEC of 7/8 it means he is not wasting any bandwidth at the cost of delivering a signal. The
lower amount of error correction means that more sophisticated equipment receiving end (for
example a more stable and sensitive LNB, or higher reserves e needed compared to the same
Television encoding systems by nation; countries using the PAL system is shown in blue.
PAL, short for Phase Alternate Line, is an analogue television encoding system used in
broadcast television systems in many countries. Other common analogue television systems
are SECAM and NTSC.
3.5.1 COLOUR ENCODING
The basics of PAL and the NTSC system are very similar; a quadrature amplitude modulated
subcarrier carrying the chrominance information is added to the luminance video signal to
form a composite video baseband signal. The frequency of this subcarrier is 4.43361875
MHz for PAL, compared to 3.579545 MHz for NTSC. The SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarriers
4.25000 and 4.40625 MHz.
The name "Phase Alternating Line" describes the way that the phase of part of the colour
information on the video signal is reversed with each line, which automatically corrects phase
errors in the transmission of the signal by cancelling them out, at the expense of vertical
frame colour resolution. Lines where the colour phase is reversed compared to NTSC are
often called PAL or phase-alternation lines, which justifies one of the expansions of theacronym, while the other lines are called NTSC lines. Early PAL receivers relied on the
imperfections of the human eye to do that cancelling; however this resulted in a comblike
effect known as Hanover bars on larger phase errors. Thus, most receivers now use a
chrominance delay line, which stores the received colour information on each line of display;
an average of the colour information from the previous line and the current line is then used
to drive the picture tube. The effect is that phase errors result in saturation changes, which are
less objectionable than the equivalent hue changes of NTSC. A minor drawback is that the
vertical colour resolution is poorer than the NTSC system's, but since the human eye also has
a colour resolution that is much lower than its brightness resolution, this effect is not visible.
In any case, NTSC, PAL and SECAM all have chrominance bandwidth (horizontal colour
detail) reduced greatly compared to the luminance signal.
Kong and Macau, standards D/K in most of Central and Eastern Europe and Standard D in
mainland China. Most analogue CCTV cameras are Standard D.
7-MHz channels are used in VHF (B, D) and 8-MHz channels in UHF (G, K, I), although
Australia used 7-MHz channels in UHF and Ireland uses 8-MHz channels in VHF.
3.6 DESCRIPTION
This TV transmitter consists of an exciter section consists, Visual and Aural Power Amplifier
section(A), Visual Last stage P A section (B) and external devices. It delivers 1.0KW output
and 2-2.5KW aural output. The power supply and control Circuits of this transmitter are
common to both visual and aural transmitters.
Parts of power supply:
1. Main Power Supply AC 200V (3-P) 50/60 Hz.
2. Internal illumination & receptacle Power Supply AC IOOV (I-P) 50/60 Hz.
3.7 EXCITER SECTION
The exciter section consists of fully solid-state visual and aural exciters and s the subsequent-
stage vacuum Power Amplifier section.
3.7.1 VISUAL EXCITER SECTION
The main components in the construction of visual exciter section are as below:
1. Visual Modulator.
2. IF Attenuator.
3. VSB Filters Phase-Compensator.
4. Mixer.
5. Output Filter.
6. Local Crystal Oscillator.
7. Visual Transistor P A & Power Supply.
3.7.2 WORKING
The input video signal is Amplitude Modulated (AM) by the visual modulator to obtain the
wave {Video Intermediate Frequency- VIF). The modulated wave is level adjusted by r andis passed through a VSB filter to reduce unwanted LSB. Phase changes in cutoff of the VSB
In satellite communications, the use of orbiting satellites is to provide communication links invarious points on earth. Communication satellites provide telephone, television, and data s
between widely separated fixed locations. The technique basically involves transmitting from
an earth station to a satellite. Equipment’s on board of the satellite receive the signals, them,
and transmit them to a region of the earth. Receiving stations within this region pick signals,
thus providing the communication link.
Satellites provide communication links via microwave radio, most commonly in the super
high frequency band of 3 to 30 GHz. (3 billion to 30 billion hertz, or cycles per second).
These frequencies correspond to wavelengths ranging from 10 cm to 1 cm (4 inches to 0.4
inches). Radio this short diverges along straight lines in narrow beams, rather than
propagating in an in spherical wave front in the manner of longer wavelengths. In order to
communicate via radio, therefore, transmitters and receivers must be situated within line of
sight of one another. On land, this can be achieved by using towers on hilltop locations, but
microwave communication across oceans is not possible without use of satellites.
The specific frequency bands open to civilian satellite communications are assigned by the,
International Telecommunication Union, based in Geneva, Switzerland. Each band consists
of an (Earth-to-satellite) frequency and a Downlink (satellite-to-Earth) frequency. The two
bands that have been in use longest, and still carry the most traffic, are the C band, with
uplink frequencies centered on 6 GHz and downlink frequencies centered on 4 GHz, and the
Ku band, uplink/downlink frequencies centered on 14/11 GHz. In order to relay signals in
these frequencies, a typical communication satellite is equipped with a number of
transponders. Each transponder consists of a receiver tuned to the uplink band, a frequency
shifter to the received signals to the downlink band, and a power amplifier to produce an
adequate sitting power.
4.1 POLARIZATION
One frequency can be used twice by using two opposing polarizations, so that the two signals
on the two identical frequencies do not interfere with each other doubles the actual number
of channels that can be transmitted in the satellite's frequency range. One way of transmitting
a signal is in linear polarization, the other way by rotating circular polarization. For the latter
The satellite used by DDK is Insat2-E. This satellite does not belong to India itself; therefore,
the service is n contract basis. May be in near future we may be using our own satellites for
the above thus making our country self-reliant in this aspect.
Currently India uses the European Meteosat-5 for its forecasting requirements. India's failed
INSAT originally provided this service. INSAT satellites are equipped with Very High
Resolution Radiometers (VHRR) in addition to their primary communication payload.
However, Most developed problems, and the only one working is on the aging Insat ID. The
Geo-sync birds, with a much higher orbit, compared to the Polar orbited Insat. India uses the
European weather Satellite INSAT which unfortunately was expected de-orbited by end
2001. Hence India has set up a new Insats program, & its launch, on a carsh, to ensure we
have a GEO Insats before Insats gets decommissioned. The number of Indian satellites to belaunched over the next two years is seven. The Indian metrological satellite insat will not be
launched into a polar orbit. Despite its rather name, India's Polar Satellite Launch Vehicle
(PSL V) will actually put Met sat into any Transfer Orbit. If successful, this will bring India
into the elite league of countries launch Geo-sync Satellites. The Indian government has
approved plans by the Indian Space Research Organization (ISRO) to advanced remote
sensing satellite, Cartosat 2, which will have an optical resolution of 1 meter. Cartosat 2 was
to be put in orbit by India's Polar Satellite Launch Vehicle (PSL V) in 2003 or 2004. Cartosat
1 (IRS-P5,) to be launched in 2002, will offer a resolution of 2.5 meters. Earlier Indian
Satellites offered a resolution of only 5.8 meters. Cartosat 2 will cost Rs 230 Crores, which is
about Rs 20 Crores less than the technically inferior Cartosat's cost of Rs 250 Cores.
Till now Doordarshan was using PAL-D system for colour TV transmission. But nowrecently it has planned to introduce high definition technology with starting of Common
Wealth Games, Delhi 2010.
5.1 HIGH-DEFINITION VIDEO
High-definition video or HD video refers to any video system of higher resolution than
standard-definition (SD) video, and most commonly involves display resolutions of
1,280×720 pixels (720p) or 1,920×1,080 pixels (1080i/1080p). This article discusses the
general concepts of high-definition video, as opposed to its specific applications in television