Training Report- radio broadcasting and captive earth station ( communication systems)

TRAINING REPORT ON

ALL INDIA RADIO BROADCASTING

Submitted in partial fulfilment of the requirements for the award of the degree of

Bachelor of Technology In Electronics and communication

Guide: Mr Piyush chanana Kumar (0271152806)

Submitted by: Vanshaj

Bharati Vidyapeeth’s College of Engineering GGS Indraprastha University, Delhi – 6

(2006-2010)

Certificate This is to certify that the industrial training report entitled “ALL INDIA RADIO BROADCASTING” done by Mr.Vanshaj kumar Roll No.0271152806 is an authentic work carried out by him at ALL INDIA RADIO, New Delhi under my guidance. The matter embodied in this project work has not been submitted earlier for the award of any degree or diploma to the best of my knowledge and belief.

Date: Guide

Signature

of

Name of the Guide: Mr.PIYUSH CHANANA Designation

2

the

Acknowledgements It is my proud privilege to acknowledge with deep sense of gratitude and devotion, the keen interest rendered to us by revered employees of ALL INDIA RADIO. I am also very thankful to our training guide Mr. Shantanu Ghosh (A.E.) and all the concerned and non-concerned instructors and members as well as the university who gave us a chance to learn a lot in the form of summer training. Without there support, it would have been difficult job to successfully complete the training . I am highly thankful to: Mr. Naveen Mahajan, Mr. Vishnu Verma ,Mr. K. N. Pandey Miss Suparna Sen Gupta, Mr. D.K. Ghosh, Mr. S. D. Singh. I want to thank the Department of Electronics and Communication of the former Bharati Vidyapeeth’s College of Engineering for giving me permission to commence this thesis in the first instance, to do the necessary research work. I have furthermore to thank the honourable Guide, Mr Piyush Chanana whose help, stimulating suggestions and encouragement helped me in all the time of research for and writing of this thesis. Especially, i would like to give my special thanks to him whose patient help enabled me to complete this work.

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ABSTRACT The objective of the thesis is to study the various sections of ALL INDIA RADIO broadcasting and appropriate execution and working of the news studios and Capitive Earth Station. All India Radio, officially known as Akashvani is the radio broadcaster of India and a division of Prasar Bharati (Broadcasting Corporation of India), an autonomous corporation of the Ministry of Information and Broadcasting, Government of India. All India Radio now under Prasar Bharati has the distinction of being one of the major broadcasting organizations in the world. The real breakthrough in news broadcasting came after January 1936 when the first news bulletin from the Delhi Station went on the air on January 19, 1936 coinciding with the starting of its transmission. The News Services Division broadcasts from Delhi 86 daily news bulletins in English, Hindi and 17 Indian languages for a duration of 12 hours and 20 minutes. The bulk of AIR news comes from its own Correspondents spread all over the country. It has 90 regular Correspondents in India and five abroad at Colombo, Dhaka, Dubai, Kathmandu, and Kabul. English News Service Available in two forms. The ‘core’ service covers major developments in diverse fields in a compact form.Good acoustics is a pre-requisite of high quality broadcasting or recording. Acoustic treatment is provided in studios, control rooms, and other technical areas in order to achieve the acoustic conditions which have been found from experience to be suitable for the various types of programmes. Sound waves emanating from a sound source are propagated in all directions. These sound waves are subject to reflection, absorption and refraction on encountering an obstacle. In any enclosed room when a sound is switched off, it takes a finite length of time to decay to inaudibility.

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The broadcast of a program from source to listener involves use of studios, microphones, announcer console, switching console, telephone lines / STL and Transmitter. A broadcast studio is an acoustically treated room. It is necessary that the place where a programme for broadcast purposes is being produced should be free of extraneous noise. Low level mixing system may look economical since it requires one single pre-amplifier for all low level inputs, but quality of sound suffers in this system as far as S/N ratio is concerned. Digital communication system falls into 3 categories in their design. They are Bandwidth efficient, Cost efficient and power efficient. These three criteria are applicable in different environments. Modulation of digital signal comes at the end of the transmission chain. Networking can be defined simply as an interconnection of two or more computers. Purpose of networking is to Sharing of files, Sharing of resources, Sharing of programs, Users communicate with each other, Video conferencing, Entertainment, distributed games. Different types of networking are LANs, WANs, and MANs. The other features are DNS( Domain name system) . The Captive Earth station consist of a satellite system.In general, a satellite system has five major components. There are the two satellite links, i.e., the uplink and the downlink, to and from the satellite. There are also two terrestrial links, connecting the two earth stations with the user sites. In general, a satellite system has five major components. There are the two satellite links, i.e., the uplink and the downlink, to and from the satellite. There are also two terrestrial links, connecting the two earth stations with the user sites. The transponder is the on-board relay station for the satellite. Its function is similar to that of a terrestrial microwave radio relay station. The on-board power supply is typically a series of solar batteries; power conservation is achieved by turning off equipment when not in use.The attitude of a satellite refers to its orientation in space. The attitude control apparatus is one of the most important pieces of equipment on-board. It prevents the satellite from spinning out of control in space and that the directional antennas point in the proper direction. The advantage of satellite technology is based on the potential for reaching wide expanses and serving discontinuous user bases without the cost of traditional terrestrial services. The training section ends up with the outside broadcasting section. Outside Broadcasts

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(abbreviated as OBs) form a substantial portion of programmes radiated from a Radio Station. Major events that occur at different parts of a country, such as sports events, important functions of political, cultural and national important and other such programmes. The study carried out for this thesis lead to significant new knowledge, which has resulted in elaborated

concepts for the sections of All India Radio

broadcasting.

CONTENTS Chapter 1 History and overview • All India radio History……………………………………….…….(9) • Services…………………………………………………………….(9) • News service division…………………………………………......(10) • Home bulletin………………………………………………….......(12) • News production…………………………………………………...(14) Chapter 2 Studio Acoustics • Introduction……………………………………………………….(20) • Sound insulation……………………………………………..……(22) Chapter 3 Studio Chain • Digital studio……………………………………………….……..(27) • Studio requirements………………………………………………(29) • Announcer console………………………………………………..(32) • Recording room…………………………………………………...(33) Chapter 4 Digital Modulation • Introduction…………………………………………………...…..(36) • Amplitude shift keying………………………………………..…..(37) • Frequency shift keying………………………………………..…...(38) • Quadrature phase shift keying……………………………......……(43)

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Chapter 5 Recording, Editing and Playback • Introduction………………………………………………………..(47) • Erase process………………………………………………………(49)

Chapter 6 Network Maintenance • Networking………………………………………………………….….…(50) • Purpose of networking…………………………………………….….…...(51) • Types of Networking……………………………………………….……..(55) • Client server Model………………………………………………….……(59) Chapter 7 Captive Earth Station And OB • Introduction……………………………………………………………….(60) • Geostationary orbit………………………………………………………..(61) • Orbital alternatives………………………………………………………...(62) • Satellite Design…………………………………………………………….(64) • Captive Earth station………………………………………………………(67) • Outside Broadcasting………………………………………………………(75) Summary and Conclusions…………………………………………………….…(80)

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LIST OF FIGURES: • • • • • • • • • • • • • • • • • •

Flow Chart for a news studio………………………………………….. (17) Flow Chart for compiler editor……………………………………….... (18) Noise criteria curve …………………………………………………….(23) Digital studio setup of AIR…………………………………………….. (27) Low level mixing………………………………………………………..(30) High level mixing…………………………………………………….....(31) Amplitude shift keying………………………………………………..... (37) Minimum shift keying………………………………………………….(39) DPSK……………………………………………………………………(42) Computer network………………………………………………………. (50) Client server model……………………………………………………… (57) Peer-to-peer model………………………………………………………. (58) Satellite communication…………………………………………………. (60) Geostationary orbits……………………………………………………... (61) Different orbits in solar system………………………………………….. (62) Satellite link………………………………………………………………(64) Captive earth station network……………………………………………. (69) Uplink setup………………………………………………………………(70)

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•

Downlink setup…………………………………………………………... (71)

CHAPTER 1 History and Overview 9

ALL INDIA RADIO HISTORY All India Radio, officially known as Akashvani is the radio broadcaster of India and a division of Prasar Bharati (Broadcasting Corporation of India), an autonomous corporation of the Ministry of Information and Broadcasting, Government of India. Established in 1936,today, it is the sister service of Prasar Bharati's Doordarshan, the national television broadcaster. The word Akashavani was coined by Professor Dr. M.V. Gopalaswamy for his radio station in Mysore during 1936. All India Radio is one of the largest radio networks in the world. The headquarters is at the Akashwani Bhavan, New Delhi. Akashwani Bhavan houses the drama section, the FM section and the National service. The Doordarshan Kendra (Delhi) is also located on the 6th floor of Akashvani Bhavan. During his regular broadcasts from the Azad Hind

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Radio, Subhas Chandra Bose used to refer to the pre-independence AIR as Anti Indian Radio.

SERVICES AIR has many different services each catering to different regions/languages across India. One of the most famous services of the AIR is the Vividh Bharati Seva (roughly translating to "Multi-Indian service"). Vividh Bharati celebrated its Golden Jubilee on 3 October 2007. Vividh Bharati has the only comprehensive database of songs from the so termed "Golden Era" of Hindi film music (roughly from 1940s to 1980s). This service is the most commercial of all and is popular in Mumbai and other cities of India. This service offers a wide range of programs including news, film music, comedy shows, etc. The Vividh Bharti service operates on different MW band frequencies for each city as shown below.

EXTERNAL SERVICES The External Services Division of All India Radio broadcasts in 27 languages to countries outside of India, primarily by high powered short wave broadcasts although medium wave is also used to reach neighbouring countries. In addition to broadcasts targeted at specific countries by language there is a General Overseas Service which broadcasts in with 8 1/4 hours of programming each day and is aimed at a general international audience.

News Service Division INTRODUCTION All India Radio now under Prasar Bharati has the distinction of being one of the major broadcasting organizations in the world. The News Services Division (NSD) of All India

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Radio disseminates news and comments to listeners in India and abroad. From 27 news bulletins in 1939-40, AIR today puts more than 510 bulletins daily around 52 hours in 82 languages/dialects in the Home, Regional and External Services. Out of these, 89 bulletins are broadcast daily from Delhi in the Home Service in English, Hindi and other Indian languages. The 44 Regional News Units (RNUs) putout 355 daily news bulletins in 67 languages. This includes news bulletins mounted exclusively on FM GOLD channel from 22 AIR Stations. In addition to the daily news bulletins, the News Services Division also mounts everyday a number of news-based programmes on topical subjects from Delhi and some other Regional News Units.

EARLY HISTORY The history of news broadcasting in India is much older than that of All India Radio. The first ever news bulletin in the country went on the air from the Bombay Station on July 23, 1927 under a private company, the Indian Broadcasting Company. A month later on August 26, 1927 another bulletin in Bengali was started from the Calcutta Station. Until 1935, two bulletins, one each in English and Hindustani were broadcast from Bombay and a bulletin in Bengali was broadcast from Calcutta. The Indian Broadcasting Company went into liquidation in March, 1930 following which broadcasting came under the direct control of the Government of India. The service was designated as the Indian State Broadcasting Service. It was renamed All India Radio on June 8, 1936.

DEVELOPMENT

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The real breakthrough in news broadcasting came after January 1936 when the first news bulletin from the Delhi Station went on the air on January 19, 1936 coinciding with the starting of its transmission. Besides, news bulletins in English and Hindustani, talks on current affairs were also started from the Station in both the languages. The Central News Organization was set up on August 1, 1937. Mr. Charles Barns took charge as the first News Editor in September and he later became the first Director of News. The outbreak of the Second World War in 1939 gave an impetus to the development of the Organization. The Monitoring Service was set up in 1939 to monitor foreign broadcasts. In 1943, the External Broadcast Unit was set up under the Director of News. By 1945, the Central News Organization was handling news bulletins in different Indian languages as well as in the External Services. After Independence, news broadcasts of AIR grew both in quantity and quality. More emphasis was laid on national and regional news bulletins.

HOME BULLETINS The News Services Division broadcasts from Delhi 86 daily news bulletins in English, Hindi and 17 Indian languages for a duration of 12 hours and 20 minutes. In Hindi, 21 news bulletins are broadcast for a duration of two hours 30 minutes while 20 news bulletins are put out in English everyday for a duration of 2 hours and 25 minutes. These include two Sports news bulletins one each in Hindi and English. Apart from Hindi, forty-time news bulletins in 17 Indian languages for a duration of 7 hours and 45 minutes are broadcast everyday. The importance of language bulletins lies in the fact that they are the main source of national, international and regional news for the masses in small towns and villages. The evening bulletins in Dogri, Kashmiri and Urdu also include a commentary on topical subjects.

REGIONAL BULLETINS

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Regional bulletins were introduced in the early fifties. The first news bulletins in regional languages were started in April, 1953 from Lucknow and Nagpur Stations. In 1954-55, Regional News Units were set up at Bombay, Madras and Calcutta. This went on steadily and at present there are 45 Regional News Units functioning in different parts of the country. 146 news bulletins in 66 regional languages/dialects including English and Hindi are broadcast for a duration of 19 hours and 35 minutes.

BULLETINS ON FM-Gold CHANNEL The then Information and Broadcasting Minister launched a news and entertainment channel called AIR FM-II (now called FM Gold) on September 1, 2001. The Channel is on the air for about 18 hours a day from 6 am to 10 minutes past 12 in the night. It is a composite blend of information and entertainment with one third of its contents devoted to news and current affairs. The Channel carries news on the hour originating from Delhi. Composite news programmed in Hindi and English originating from Delhi are exclusively broadcast every morning, midday and evening for a duration of 30 minutes each.

RADIO NEWSREEL Radio Newsreel was started on December 10, 1955 both in English (Radio Newsreel) and Hindi (Samachar Darshan) from Delhi. Newsreel in English is broadcast on Monday, Tuesday, Thursday and Saturday while Samachar Darshan is broadcast on Wednesday, Friday and Sunday. Some Regional News Units also put out regional Newsreels in the respective regional languages.

NEWS ON PHONE SERVICE AIR news on Phone was introduced on February 25, 1998 from Delhi. The service provides the latest news highlights in Hindi and English to a listener anywhere in the world on phone on dialing the specified numbers. Later, the News on Phone’ service in Tamil from Chennai, in Telugu from Hyderabad, in Marathi from Mumbai and in Hindi from Patna were also introduced. This same service has also been started from the 14

Regional News Units at Ahmedabad, Thiruvananthapuram, Bangalore and Jaipur in 2006 and from Imphal and Lucknow in 2007. SOURCE OF NEWS The bulk of AIR news comes from its own Correspondents spread all over the country. It has 90 regular Correspondents in India and five abroad at Colombo, Dhaka, Dubai, Kathmandu, and Kabul . Apart from this, AIR has around 500 Part-time Correspondents based at nearly all district headquarters. The PTCs are to meet the requirements of Doordarshan News also. NSD subscribes to the news agencies UNI, PTI and their corresponding Hindi services – Univarta and Bhasha, and ANI to make its bulletins broad-based. Another source of news are the Monitoring Units (English and Hindi) attached to the General Newsroom and the Central Monitoring Services, which monitor the bulletins of major broadcasting organisations of the world. A Radio News Exchange Programme was initiated with the members of the Asia Pacific Broadcasting Union to broaden the news coverage. An Information Technology Unit was set up at Delhi to take care of the IT requirements of NSD. The Unit has set up an internal Website to cater to the news requirements of the Regional News Units and others.

NEWS PRODUCTION SERVICES OFFEREDEnglish News Service Available in two forms. The ‘core’ service covers major developments in diverse fields in a compact form. A more comprehensive segmented service allows papers to pick additional inputs from segments of their choice. National/Regional, Economic/Commercial, International, and Sports. Core service puts out about 40,000 words and the full segmented service upto 100,000 words per day. 1.)BHASHA Bhasha is the Hindi language news service of PTI. With its own network in the Hindi-

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speaking states and drawing on PTI files, Bhasha puts out about 40,000 words per day. 2.)STOCK SCAN A screen-based service providing stock market information from major stock exchanges of the country.

3.)NEWS SCAN Displays news in capsule from on video monitors. Major developments in the country and

abroad

are

covered.

4.)DATA INDIA A reference weekly providing a digest on the happenings in India, in a user-friendly alphabetical listing. 5.)ECONOMIC SERVICE A fortnightly journal providing analytical reports on the state of the Indian economy and trends

in

the

corporate

world.

A weekly package of eleven special stories on topics ranging from arts to business to science. 6)ASIA PULSE An on-line data bank on economic developments and business opportunities in asian countries. Formed by PTI and four other Asian media 16rganizations, Asia Pulse International is registered as a company in Singapore.

NEWS SOURCES

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PTI(PRESS-TRUST OF INDIA)

 India’s largest news agency, Press Trust of India is a non-profit sharing cooperative owned by the country’s newspapers. PTI subscribers include 450 newspapers in India and scores abroad. All major TV/Radio channels in india and several abroad, including BBC in London, receive the PTI Service. With a staff of over 1,300 including 400 journalists, PTI has over 80 bureaus across the country and foreign correspondents in major cities of the world including Beijing, Dhaka, Jerusalem, Johannesburg, Islamabad, Kathmandu, Kuala Lumpur, London, Moscow, New York, Washington and Sydney.  In addition, about 475 stringers contribute to the news file at home. It has arrangements with the Associated Press (AP), Agencies France Presse (AFP) and Bloomberg for distribution of their news in India, and with the the Associated Press for its Photo Service and International commercial information. PTI exchanges news with nearly 100 news agencies of the world as part of bilateral and multilateral arrangements, including Non-Aligned News Agencies Pool and the Organisation of Asia-Pacific News Agencies.

UNI(UNITED NEWS OF INDIA) United News of India is one of the two primary Indian news agencies. It works in collaboration with several foreign news agencies and partners, including Reuters and DPA. UNI began its operations on March 21, 1961, though it was registered as a company in 1959. Its head office is located in New Delhi. It employs approximately 325 journalists around India and 250 "stringers" covering news events in other parts of the world, with correspondents in Washington, London, Dubai, Islamabad, Dhaka, Colombo, Kathmandu, Singapore and Sydney. UNI serves roughly 1000 subscribers globally.

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ANI: ANI is South Asia's leading Multimedia News Agency providing content for every information platform, including TV, Internet, broadband, newspapers and mobiles. We provide unmatched news coverage from South Asia including breaking news and features with regional perspectives, along with politics, business, health, technology, travel and entertainment content. The New Delhi head office is staffed by professionals round the clock 365 days a year.. where news content is collected, packaged and delivered

in

various

FLOWCHART FOR A NEWS STUDIO

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formats.

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FLOWCHART FOR COMPILER EDITOR

Radio broadcasting is a Government of India monopoly under the Directorate General of All India Radio--established in 1936 and since 1957 also known as Akashvani--a government-owned, semicommercial operation of the Ministry of Information and Broadcasting. From only six stations at the time of independence, All India Radio's network had expanded by the mid-1990s to 146 AM stations plus a National Channel, the Integrated North-East Service (aimed at tribal groups in northeast India), and the External Service. There are five regional headquarters for All India Radio: the North Zone in New Delhi; the North-East Zone in Guwahati, Assam; the East Zone in Calcutta; the West Zone in Bombay; and the South Zone in Madras.

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CHAPTER 2

STUDIO ACOUSTIC

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STUDIO ACOUSTIC

INTRODUCTION A broadcasting studio is a room in studio complex which has been specially designed and constructed to serve the purpose of originating broadcasting programs. Whenever any musician sings and we sit in front of a performing musician to listen to him, we enjoy the program by virtue of the superb qualities of our sensory organs namely ears. However, when we listen to the same program over the broadcast chain at our home though domestic receivers, the conditions are entirely different. We as broadcasters, are continuously engaged in the task of ensuring the maximum pleasure for the listener at home when the artists are performing inside the studios. In order to achieve our goal we must thoroughly understand the characteristic of the different components involved in the broadcast chain, and in this process we must preserve the original quality of sound produced by the artists inside the studio. The science of sound is often called “Acoustics’. It would be thus prudent to understand the field of acoustics as applied to broadcasting.

ACOUSTIC TREATMENT Good acoustics is a pre-requisite of high quality broadcasting or recording. Acoustic treatment is provided in studios, control rooms, and other technical areas in order to achieve the acoustic conditions which have been found from experience to be suitable for the various types of programmes. In this section problems and design aspects of internal acoustics of a broadcast studio are explained.

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a)

Propagation of Sound Waves Sound waves emanating from a sound source are propagated in all directions. These sound waves are subject to reflection, absorption and refraction on encountering an obstacle. Extent to which each of these phenomenon takes place depends upon the structure and shape of the obstacle, and also on the frequency of sound waves. In close rooms, the sound would be reflected and re-reflected till the intensity weakens and it dies down. Physical characteristics of sound waves are thus modified in various ways before they reach the human ear. These reflected waves can create echo effect in the room. To achieve the desirable effects of the reflected sound, the dimensions and shape of the room are decided with due care and acoustic treatments are also provided on the various surfaces.

b)

ACOUSTIC ABSORBERS

Acoustic absorbers are provided on the inner surfaces of the room to achieve optimum R/T characteristics. Different absorbers have different absorption characteristics. No single absorber generally provides uniform absorption over the complete frequency spectrum. Some of the commonly used absorbers are: i) Porous Materials: Mineral wool, glass wool, etc. are members of this class. These materials are very good absorber and are most effective in mid and high frequencies, however, these cannot be used without some facing material. ii) Fibrous Materials: Celotak, insulation boards, perfotiles, jolly-lowtone tiles etc. fall in this category. Absorption of these materials depends upon their softness. Absorption efficiency of these materials depends upon the trapping and dissipation of sound energy in tiny pores. Absorption gets reduced if the surface pores are filled with paints etc.

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ii)

Panel Absorbers: Panel absorbers are thin sheets/membranes with an air cavity behind. The mass of the panel and the springiness of the air in the cavity resonant at some particular frequency.

Sound Insulation The ‘unwanted sound’ or ‘noise’ in the studios spoils the quality of recorded programmes. Sound insulation of walls doors etc. and layout of the studio building is therefore, decided for acceptable background noise level in the studios. a)

Acceptable background Noise Level

It is not possible to specify an acceptable background noise level in the studios as a single weighted figure, because the noise normally present is spread over a wide range. An excessive noise energy over a small bandwidth could be very disturbing without very much affecting the weighted noise figure. Therefore, the acceptable background noise level is specified as a graph of band level in octave bands against frequency, usually over the range 68 Hz to 4 kHz. These acceptable limits have varied widely between different authorities. In AIR NC 20 curve is followed for studios (Refer Figure 3 for NC Curve), which corresponds to following values.

Frequency Band (Hz)

Noise Level (db above 0.002 dynes/cm2)

37.75

54

75.150

43

150.300

35

300.600

28

600.1200

23

24

1200.2400

20

2400.4800

17

4800-9600

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Fig. Noise Criteria Curve b)

Source of Noise and Sound Insulation

Noise in studios may be either air-borne or structure borne. Background noise in a studio can originate from

c)

•

Outside the building

•

Inside the studio itself and /or

•

Outside the studio but within the building

Noise originated from outside the building

Noise from outside the studio building are mostly due to aircraft, road and rail traffic etc.

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These noise can be avoided/minimised by locating the studio building in a quiet environment away from the railway lines highways and aerodromes. In case studio centre is located in noisy street, sufficient set-back distance is provided between the street kerb and the main building. Sometimes a multi-storeyed office building is built in between the studio building and the sound source to act as a sound barrier for the studio building.

d)

Noise from inside the studio

Noise from inside the studio itself consist of air-conditioning noise due to air flow, the noise from fluorescent lights, from cooling fans in tape recorders etc. Noise due to airflow in the studios is controlled by creating slow diffusions of air. To avoid noise of fluorescent lights, ballast chokes are not mounted with the light fittings in the studio. These are mounted separately in a ballast nitch outside the studio. Cooling fans in tape recorders are generally of low noise type. e)

Control of air-conditioning and diesel generator and lift noise

Noise due to air-conditioning plants can transfer to the studios as structural borne noise as well as air borne noise. The structural borne noise is avoided by providing the a.c. plants in a separate block isolated from the main studio mook. A structural isolation gap of 75 mm width right from foundation level up to the roof height is provided between the two blocks. This gap is filled with damping materials, such as asphalt, to avoid bridging by stone, cement mortar etc. Wherever required, only flexible connections are used for linking these blocks for running electrical cables, duct etc. These plants are mounted on vibration isolation pads and water pipes for condenser cooling are also isolated from the walls with resilient packing materials so that transmission of the vibration to the building is avoided.

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To avoid transferred structural vibration through ducts, the main supply and return ducts from the plants are connected to the studio ducts through flexible canvass connection. To avoid transfer of airborne noise from the a.c. plants, the plenum chamber and the entire length of supply/return duct is insulated internally with sound absorbing materials e.g. glass wool. Also speed of the blower is kept low (about 750 rpm) as the noise at source itself is controlled. Similarly diesel generator is either installed in this structurally isolated block or in a separate building away from the studio. The generator is mounted on anti-vibration mounting so that vibration due to the same is minimised in the structure. f)

Sound insulation from footfall, dragging of furniture etc.

Noise due to footfall, dragging of furniture, falling of paper weight etc. are transmitted at long distance as structure borne noise. Transmission of this noise is much more in steel framed buildings than in load bearing structure. Therefore, studios are generally made in load bearing single storeyed buildings. In case of steel-framed building and/or multi-storeyed buildings, floating construction i.e. box within the box is recommended for broadcasting studios. g)

Sound Insulation from adjacent room/corridor noise

High level of programme/ monitoring in adjacent rooms and conversation in corridors may cause leakage of this sound in a studio. This leakage may be due to poor sound insulation of intervening walls or due to flanking paths.

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CHAPTER 3

STUDIO CHAIN IN AIR STATION

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INTRODUCTION The broadcast of a program from source to listener involves use of studios, microphones, announcer console, switching console, telephone lines / STL and Transmitter. Normally the program originate from a studio centre located inside the city/town for the convenience of artists.

The program could be either “live” or

recorded”. In some cases, the program can be from OB spot, such as commentary of cricket match etc.

Programs that are to be relayed from other Radio Stations are

received in a receiving centre and then sent to the studio centre or directly received at the studio centre through RN terminal/telephone line. All these programs are then selected and routed from studio to transmitting centre through broadcast quality telephone lines or studio transmitter microwave/VHF links.

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STUDIO CENTRE The Studio Centre comprises of one or more studios, recording and dubbing room, a control room and other ancilliary rooms like battery room, a.c. rooms, switch gear room, DG room, R/C room, service room, waiting room, tape library, etc. The size of such a centre and the number of studios provided depend on the program activities of the station. The studio centre in AIR are categorized as Type I, II, III and IV. The number of studios and facilities provided in each type are different. For example a type I studio has a transmission studio, music studio with announcer booth, a talks studio with announcer booth, one recording/dubbing room and a Read Over Room. Type II has one additional drama studio. The other types have more studios progressively.

BROADCAST STUDIO A broadcast studio is an acoustically treated room. It is necessary that the place where a programme for broadcast purposes is being produced should be free of extraneous noise. This is possible only if the area of room is insulated from outside sound. Further, the microphone which is the first equipment that picks up the sound, is not able to distinguish between wanted and unwanted signals and will pick up the sound not only from the artists and the instruments but also reflections from the walls marring the quality and clarity of the programme. So the studios are to be specially treated to give an optimum reverberation time and minimum noise level. The entry to the studios is generally through sound isolating lobby called sound lock. Outside of every studio entrance, there is a warning lamp, which glows ‘Red’ when the studio is ‘ON-AIR’. The studios have separate announcers booths attached to them where first level fading, mixing and cueing facilities are provided.

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Studio Operational Requirements Many technical requirements of studios like minimum noise level, optimum reverberation time etc. are normally met at the time of installation of studio. However for operational purposes, certain basic minimum technical facilities are required for smooth transmission of programmes and for proper control. These are as follows:

•

Programme in a studio may originate from a microphone or a tape deck, or a turntable or a compact disc or a R-DAT. So a facility for selection of output of any of these equipments at any moment is necessary. Announcer console does this function.

•

Facility to fade in/fade out the programme smoothly and control the programme level within prescribed limits.

•

Facility for aural monitoring to check the quality of sound production and sound meters to indicate the intensity (VU meters).

•

For routing of programmes from various studios/OB spots to a central control room, we require a facility to further mix/select the programmes. The Control Console in the control room performs this function. It is also called switching console.

•

Before feeding the programmes to the transmitter, the response of the programme should be made flat by compensating HF and LF losses using equalised line amplifiers.(This is applicable in case of telephone lines only)

•

Visual signalling facility between studio announcer booth and control room should also be provided.

•

If the programmes from various studios are to be fed to more than one transmitter, a master switching facility is also required.

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MIXING As already mentioned, various equipments are available in a studio to generate programme as given below: •

Microphone, which normally provides a level of –70 dBm.

•

Turntable which provides an output of 0 dBm.

•

Tape decks which may provide a level of 0 dBm.

•

CDs will also provide a level of 0 dBm.

The first and foremost requirement is that we should be able to select the output of any of these equipments at any moment and at the same time should be able to mix output of two or more equipments. However, as we see, the level from microphone is quite low and need to be amplified, so as to bring it to the levels of tape recorder/ tape decks. Audio mixing is done in following two ways: i)

Required equipments are selected and then outputs are mixed before feeding to an amplifier. This is called low level mixing (Fig. 2). This is not commonly used now days.

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Fig. 2 Low level mixing

Low-level output of each equipment is pre-amplified and then mixed. This is called high level mixing. (Fig. 3).

Fig. 3 High level mixing Low level mixing system may look economical since it requires one single pre-amplifier for all low level inputs, but quality of sound suffers in this system as far as S/N ratio is concerned. Noise level at the input of best designed pre-amplifier is of the order of – 120 dBm and the output levels from low level equipment –70 dBm. In low level mixing, there is signal loss of about 10 to 15 dB in mixing circuits. Therefore, the S/N ratio achieved in low level mixing is 35 to 40 dB only. High level mixing system requires one pre-amplifier in each of the low level channels but ensures a S/N of better than 50 dB. All India Radio employs High level mixing.

33

Announcer Console Most of the studios have an attached booth, which is called transmission booth or Announcer booth or play back studio. This is also acoustically treated and contains a mixing console called Announcer Console. The Announcer Console is used for mixing and controlling the programmes that are being produced in the studio using artist microphones, tape playback decks and turn tables/CD players. This is also used for transmission of programmes either live or recorded. The technical facilities provided in a typical announcer booth, besides an Announcer Console are one or two microphones for making announcements, two turn tables for playing the gramophone records and two playback decks or tape recorders for recorded programmes on tapes. Recently CD and Rotary Head Digital Audio Tape Recorder (RDAT) are also included in the Transmission Studio. Control Room For two or more studios set up, there would be a provision for further mixing which is provided by a control console manned by engineers. Such control console is known as switching console. Broad functions of switching console in control room are as follows: •

Switching of different sources for transmission like News, O.Bs. other

satellite based relays, live broadcast from recording studio. •

Level equalisation and level control.

•

Quality monitoring.

•

Signalling to the source location.

•

Communication link between control room and different studios.

34

RECORDING ROOM A block schematic of a typical recording room is shown in figure 12. Two numbers of CTRs and two numbers of Push Button switches have been shown. Outputs from various studios and switching consoles have been given to multiple pads 1,2,3 and 4. Outputs from the multiple pads are wired to PB switches. Three numbers of receptacles for cassette outputs have been provided. Transformers T1 and T2 transform the output impedance of the cassette recorder to 600 ohm. The output of CTR # 1 is wired to PB switch # 2 through MP # 6. With this arrangement output of CTR # 1 can be recorded on CTR # 2. Please carefully note the impedances and levels at various points. Red and green lamps are provided on the control panel for indications from and to control room and studios.

35

DUBBING ROOM A block schematic of a typical dubbing room is shown in figure 11. The arrangement is similar to the recording room except that an additional tape deck and a mixer unit have been provided. This arrangement allows mixing of programmes. Loud Speakers A loudspeaker performs an opposite function to a microphone, i.e. it converts electrical signal into sound wave. Moving Coil or dynamic loudspeaker It consists of a permanent magnet and a voice coil for carrying audio signals. Voice coil is having a few turns of wire, wound on paper, plastic or aluminium former. It is attached to a peper that radiates sound. The coil is suspended with the help of “spider”, made of flexible material. Spider permits forward backward motion but no lateral motion. When audio currents from an amplifier flows through the coil, it produces a magnetic field around the coil. This field is at right angle to the field of permanent magnet. The two fields attract or repel each other, depending on the position of the permanent magnet.

The voice coil and the cone assembly move corresponding to the audio

currents. The resulting cone vibrations produce air pressure variation in correspondence with the audio signal. In hi-fi applications two or more speakers are used to cover the full audio range. To reproduce high frequencies, it is common to attach a dome of fabric or plastic material to the coil than to the cone, thus forming a dome “tweeter”. Low frequency speakers known “woofers” are of large size. The middle range speakers are called “squeakers”.

36

Speaker Impedance Normally such speakers are designed with impedances of 2,3,5,8,9,16,32 ohms. When several speakers are connected in parallel as in the case of column units then their phase must be checked. This is done by feeding currents from a Torch cell through a switch. While switching it on every time the position of the cone is watched whether it is moving inwards or outwards. In fact all the cones should behave identically so that their outputs are together. Whenever any cone movement is to be reversed its connections at the terminals may be interchanged to get the sound output in phase. The matching of the loud-speakers impedance with the output impedance of a monitoring amplifier is important. This is done by suitable series parallel combinations in the speakers to approach the amplifiers impedance. If the permanent magnet has become weak or the paper cone is torn off, the loudspeaker may be replaced. By listening to poor quality, the ears lose the discrimination of good and bad quality programme. Therefore, monitoring speakers should be the best available. Headphones Headphones basically work on the same principles which are applicable to loudspeakers. However, with headphones the acoustical loading is achieved by intimacy of the ear units to the ears. Thus even very small units are capable of providing very good bass performance. Most headphones used for high quality applications are either moving coil or electrostatic. Headphone impedances range from 4 to 1000 ohms. Specifications of a stereo headphone type EM 6201 (Philips) are given below : Frequency range

20 to 20 kHz

Matching impedance

4 to 32 ohms

Maximum input

0.1 watt.

37

CHAPTER 4 DIGITAL MODULATION

38

DIGITAL MODULATION Introduction Digital communication system falls into 3 categories in their design.

They are

Bandwidth efficient, Cost efficient and power efficient. These three criteria are applicable in different environments. Radio spectrum is no more a luxury. And for broadcasters the digital system should be able to deliver within the BW available whereas mobile communication system like Cell Phone or a pager etc. must be both power and cost efficient. Modulation of digital signal comes at the end of the transmission chain. The packetised, encoded data is to be transmitted over the medium to the end user. The medium of transmission could be satellite, terrestrial or cable. Besides bandwidth one of the other criteria for the design of digital system is the ruggedness of the system, immunity from multi-path and environmental degradation. COFDM is a type of transmission to meet these challenges. Here we shall discuss the basic digital modulation techniques of ASK, FSK, PSK, QPSK & QUAM

39

1)ASK (Amplitude Shift Keying) The simplest forms of band pass data modulation is ASK. Here the symbols are represented by discrete amplitudes of fixed frequency. Digital data is nothing but bits of 0 and 1 .To represent 0 and 1 the carrier is turned on or off. Hence this is also called as On-Off keying (OOK). Alternately we can use 2 amplitudes to represent 0 & 1. 1 0

If more than 2 symbols are used then M levels of ASK process is involved where different amplitudes levels are used to represent different symbols.

c+ω n c-ω m ω ω

Cos(ω mt)

=ω n

Cos(ω ct)

The figure indicates the ASK process. multiplied by carrier Cos ω ct.

The base band signal stream Cos ω mt is

In other words the digital bit stream changes the

different levels of the carrier. 2)Frequency Shift Keying (FSK) Here the frequency is switched from one frequency to another to represent 2 symbols. The modulator switches between two carriers of different frequencies to represent 2 symbols. This is shown in the diagram.

40

Cos(ω 1t) Data

Switch Cos(ω 2t)

Alternatively a

VCO (Voltage controlled oscillator) can be used as source for

frequency shift keying. If the frequency shift can be minimised to 90 degrees phase shift , the same is known as Minimum shift keying. The spectrum of FSK is dependent on the frequency of each symbol state. The spectrum looks like as shown below.

Composite FSK ASK1

ASK2 f1

f2

Filtered FSK For controlling spectral occupancy filter is used before the FSK modulator where the bits (pulses) are shaped or smoothened. The filter used is normally a Gaussion low pass filter (GLPs). And the output is called as Gaussion Minimum shift keying (GMSK).

GMSK

GLPS

VCO

41

Detection of FSK A simplest way of detection of FSK is shown below. Here the modulated signal is filtered by 2 filters f1 & f2 which represents two different symbol states. Each filtered signal is detected and fed to Comparator, which reconstructs the bit stream.

f1

Comparator

f2

Coherent FSK detection is also possible as shown below.

Here the incoming

modulated signal is mixed with two frequencies equal to the symbol carrier frequencies. Further it is filtered and sent to Comparator, which recovers the digital signal.

f1

Cos ω 1t

Comparator

Cos ω 2t

Advantages of FSK -

Not amplitude sensitive

-

No accurate frequency control is required, as only absolute change is essential.

Disadvantages of FSK

42

-

Bandwidth efficiency is poorer than PSK

-

Bit/symbol error rate is poorer than PSK

3)Phase Shift Keying (PSK) Here the phase of the carrier is changed by 180 o absolutely to indicate another symbol. The receiver watches for the changes in phase of incoming signal to recover the symbol. 0

Phase Change

1

0

Phase Change

If the instant of phase change is indicated by a symbol it is known as differentially coherent PSK. The spectral occupancy is similar to ASK. PSK Modulator Cos (ω ct)

Switch

Figure shows a simple PSK Modulator. The carrier phase is shifted by 180 degrees to represent two symbol states. Here the Carrier Cos(ω ct) is passed through a phase changer and then fed to a switch. The switch switches either of the carriers as per the digital signal. Output is filtered for band limiting.

43

Detection Only Coherent detection is possible in PSK. The figure gives the blocks of PSK detection.

Cos (ωct+θ)

Perfect locking of carrier is required in this detector. There are many methods by which locking can be ensured. One is by sending a reference signal. Costas loop (2 phase locked loops), differential encoder etc. are also used for this purpose at the decoder.

4)Differential Phase Shift Keying (DPSK) While recovering the data from the Carrier there may be ambiguity due to phase changes by noise. To minimise this effect differential data encoding is used. “Exclusive OR” gate is used for this purpose. The coming bit is compared with previous one. 1 is sent if there is a change and a zero (0) for no change. Decoding is simple as shown in the given figure. Arbitrary Starting

1011010

01101100

01101100 Delay = Ts

44

Logic 1 = Change Logic 0 = No change

Logic 1 = Change Logic 0 = No change Logic X = Don't Care

Delay TS

5)M'ary Systems

In this case different amplitudes are chosen to represent different symbol states. If ‘n’ number of bits are to be transmitted/symbol then we require 2 n states of amplitude i.e. with 8 states we can represent 3 bits (23 = 8). Advantage: BW efficiency is good. More bits can be transmitted. Data transfer is fast. Disadvantage : More immune to noise. Receiver will be complicated and costly. M'ary FSK is more noise immune than m'ary ASK, because noise normally affects amplitude than phase.

6)QPSK Modulator (Quadrature phase shift keying) This is the most commonly used modulation scheme in digital satellite communications. Sometimes this is known as 4 QUAM (Quadrature amplitude modulation) as there are 4 states of symbols - one in each quadrant. In this carrier is modulated with 4 phase states 0o, 90o, 180o, 270o or 45o, 135o, 225o, 315o. This is called QPSK. Due to orthogonality the information can be sent twice the speed of BPSK. Data is split into 2 streams and filtered before modulated orthogonal. The coding employed is known as gray coding as the symbol change is only 1 bit in

45

successive symbols. In QPSK we can send 2 bits /symbol as shown in the constellation diagram. Gray Coding 00 01 11 1

0

Bandwidth efficiency = 2 bits/sec./Hz

Serial data

Serial to Parallel

Cos ω ct

01

00

10

10

X

Sin ω ct

QPSK Demodulator The detection of QPSK signal is shown in the block diagram given below. It is a coherent detector requiring carrier recovery and symbol timing recovery. A process known as “4th power process” is used for accurate carrier recovery. Incoming signal is mixed with a carrier in two channels with 90o shift. This is filtered and removed. Further symbol timing is recovered. Then the bit stream from each channel is serial converted.

46

Comparator Carrier recovery

Input 90

Symbol timing

o

Comparator

.

47

Parallel to Serial

Output

CHAPTER 5 MAGNETIC TAPE RECORDING, EDITING AND PLAYBACK

48

INTRODUCTION Magnetic tape recording system has got many special features, which makes it unique in Sound Broadcasting, Television and Computer field. These are :I. II.

Instant and simultaneous replay during recording. The recording medium i.e., the magnetic tape can be used again and again after erasing the previous recordings, which generally takes place along with the recording of the new program.

III.

The editing is simple and accurate. This can also be done electronically, without physically cutting the tape.

These facilities combined with excellent quality and reliability has made magnetic recording system very popular in the field of entertainment and all direct recordings are first done on magnetic tape. The System

The magnetic tape recording system may be studied under three sub-systems : I.

The magnetic system comprising the magnetic tape plus record, replay and erase heads.

II.

Tape transport system comprising the two spooling motors, the capstan motor, the brake mechanism and the control cum interlock system.

49

RECORDING PRINCIPLES The magnetic material used in recording is magnetic oxide of iron Fe2O3 and Fe2O4 or a suitable mixture of the two with small quantities of the oxides of Nickel and Cobalt. This is mixed with suitable adhesives, plasticizers, fillers etc. and applied in the form of an extremely smooth, even and thin coating (0.4 to 0.6 mils) on to a PVC backing (1.0 to 1.5 mils thick). This magnetic coated tape has a remanance of about 500 to 1000 gausses, coercivity of about 300 to 500 oersteds. The permeability is rather low (5 to 10). This tape gets magnetized when it comes in contact with a recording head with audio frequency signal currents flowing through the head windings, and as it passes on forward, retains the magnetism induced, due to the magnetic properties of remanance and coercivity. Thus if the tape is moved across the head at a constant speed of V cm/sec. and the signal current is of frequency "f" Hz, the signal current variations in time, will be recorded as magnetic intensity variations along the tape length. Thus a single cycle will be recorded on a tape length V/f cm.

This is called recorded

wavelength and will be given by λ=

v . f

So in tape recording, we really record wavelengths and from a recorded wavelength any frequency signal can be obtained by running the tape at play back speeds different from the one at the time of recording. Normally, the record and replay speeds are exactly the same for a faithful reproduction of the recorded signal. For a fixed frequency audio signal pure tone, the magnetic conditions on the so magnetized tape can be approximately depicted in the form of recorded wave lengths condition of an array of half wave bar magnets placed end to end along with the tape length as shown in figure 4.

50

THE ERASE PROCESS Erasing the previously recorded signal is essential for using the tape repeatedly.

A

satisfactory method for this is to feed the erase head with a high amplitude signal of about 100 kHz and the tape passes over this erase head before it passes on to the record head (see fig. 6). In this arrangement every part of the tape passes the erase head gap (about 15 mil) and is subjected to about 200 cycles of alternating magnetic field, starting from low value at the start of the gap, increasing to saturation value in the middle of the gap and again steadily dropping to low value of the field, as the tape leaves the gap. These repeated magnetizing cum de-magnetizing cycles erase the signal completely and leave the tape in completely unmagnified form similar to a virgin tape without a magnetic history. We note that for effective erasure, the magnetic material should be subjected to about 100 to 200 alternating magnetic cycles. On erase head this is achieved by a current of about 100 kHz frequency as the tape stays in the erase head gap for a very short duration about one millisecond. In contrast, we use the line current of 50 Hz in bulk erasure and the whole of the magnetic tape remains in the magnetic field for about 2 to 3 seconds to complete the erasure with the same result.

MAGNETIC TAPE Before we conclude the discussions on magnetic recording system, some knowledge about the magnetic tape qualities and defects are considered essential for professional grade sound recording and reproduction. Some important mechanical and magnetic properties are given below for guidance.

Tensile Strength

The tape should stand a steady pull of 3.5 Kg. Wt. and impulse load test of 100 gm. falling from a height of 250 mm.

51

Elastic Elongation

Residual elongation should not be more than 0.3% for a steady load of 1 Kg. Wt. for 24 hours.

Overall Thickness

0.050 mm + 0.005 mm.

Coating Thickness

Max. 0.015 mm min. 0.01 mm.

Smoothness of Coating

Better than 0.001 mm.

Cup and Curl

Tape should be free from coupling and curling defects on visual inspection.

Layer to layer Adhesion

Tape shall show no sticking

52

CHAPTER 6 Network Maintanance

NETWORKING

53

Networking can be defined simply as an interconnection of two or more computers as in fig.1. This can be attained by connecting with optical fiber cables or UTP Cables. Recently the wireless networking has become popular because of its mobility .

Fig. 1: A computer network

PURPOSE OF NETWORKING

54

Sharing of files The file from one computer can be shared to another computer.

Sharing of resources. In a office scenario network printers are the most cost effective sharing of resource. Hard disk space can also be shared. Sharing of programs Instead of providing each and every clerk with a word program we may provide a server based office suite which will be cost effective. Users communicate with each other. Networking can be used for communication between two computers in text form. If sound cards are installed voice can also be interchanged like intercoms with chat programs. Video conferencing This is also a part of communication in which the picture and voice can also be transmitted to the other computer. This has attained great popularity along with internet as the expatriate population has increased. The only viable communication channel is video conferencing with instant messengers.

Entertainment, distributed games Audio & video streaming 55

This has attained great popularity along with internet as the expatriate population has increased. This will satisfy the thirst for hearing their own language programs. Doom and other games This is very much popular among youngsters. The games involved are multi player games. Commerce Ticket booking, Purchase of articles and banking. During earlier times one had to travel to the booking centre for booking a ticket for flight or a train and now it can be booked through Internet. Control of equipment Domestic like washing machine, Microwave etc. In the present scenario where the employees are working for the long time and mostly they are bachelors and it will be helpful if they have machines which can be controlled through internet. For example, an employee after finishing his days work can start his microwave oven from the office and by the time he reaches his home, the food will be hot and ready.

DIFFERENT TYPES OF NETWORKING 56

LAN (Local Area Network) MAN (Metro Area Network) WAN (Wide Area Network) LAN (Local Area Network) - LAN is normally a small network within a building. MAN (Metro Area Network) - This will be connection of two networks situated in two different locations within a city. WAN (Wide Area Network) - This will be a connection of networks situated in two different cities. One more variant of this is the VPN (virtual private network) which uses public network for connecting offices in different cities. The VPN concept had improved with win 2003 and will be cheaper as it is using public network. Two modes of configuration in a network The two modes of configuration are Client Server model and the Peer to Peer model. Features of the Client Server model : This is normally suited for large networks of more than ten computers. Increased security because of central authentication of user name and password. Three level access control with NTFS file system like file level, folder level and share level. Disk space called disk quota can be allotted to the individual users depending on the requirement. Remote access from outside the city is also possible. This will be useful for the people who are moving always and has to submit regular reports to the Headquarters like our medical representatives and sales people.

57

The other features are DNS (Domain Naming System) - We know that the computers are comfortable with the numbers and the human beings are comfortable with the names. Whereas computers check for the IP address of a particular system, the human beings check for names like stit.gov.in. As a via media the DNS stores the IP address as well as the name of the computer and when the user type the IP address, it will provide the name or if the user types the name, it will take the IP address from the table. DHCP

(Dynamic Host Configuration Protocol) -

In a set up with more than

15-20 computers, it will be physically impossible to go and give static IP address to each and every computer.

The DHCP is provided with the range of IP addresses

which can be allotted whenever a computer logs in. Mailing Facility - Each and every user can be provided with an individual email address with mail server

58

One disadvantage of this type of configuration is that the operating system is 8 to 10

ADC

DC Switch Workstation

Workstation

Workstation

Client server model The system will be as in Fig.2. There will be domain controller (DC) which will be the heart of the system. The DC will contain the username and password and will authenticate the users. This will also run various services. The additional domain controller will takeover the function of the Dc when it fails. The workstations or clients will connect to the DC through a switch.

59

Features of the Peer to Peer System

Switch Workstation

Workstation

Workstation Workstation

Peer-to-peer model

60

CHAPTER 7 Introduction to captive earth station(CES)

INTRODUCTION TO SATELLITE COMMUNICATION

BASICS OF SATELLITE COMMUNICATIONS 1.0 INTRODUCTION After four decades of development, satellites have gained recognition as the key to solving many land-based transmission limitations. Today's geosynchronous, low earth orbit (LEO), and medium earth orbit (MEO) satellites enable numerous services within the telecom market. Lowering costs and innovative new services will only accelerate the growth of satellite communications markets.

1.1Types of orbits: •

Low earth orbit(450km-1000km) o Medium earth orbit(1500 km) 

Geo stationary orbit(36000 km)

Out of these the Geo stati0nary orbit is utilized for the satellite establishment. 1.1.1 Geo-stationary orbit

Figure 1.1.1 : Geostationary Orbits

The laws which are of fundamental importance in understanding satellite motion were formulated by Kepler in the 17th century and may be expressed as: a.) Each satellite moves in an ellipse with the earth at one focus b.) The area swept out by the radius vector per unit time is constant. c.) The square of the period is proportional to the cube of the orbit’s major axis. These laws lead to the general theory of orbital motion for an object constrained by a force directed towards a central point. However, we are concerned with one particular orbit – the geo-stationary orbit. This orbit is circular having a period equal to that of the earth’s rotation about its own axis and lying in the equatorial plane. The importance of the geostationary orbit lies in the fact that because its period is the same as that of the earth’s rotation, a satellite in this orbit will appear fixed in the sky and hence the receiving antenna may be aligned in a fixed direction. All other orbits would require a steered receiving aerial to track the satellite.

The geostationary orbit, being in the equatorial plane, has zero inclination. Although it is possible to have a geosynchronous orbit, that is, one which has the same orbital period as the earth’s spin period, at some inclination, this will not be geostationary. As viewed from a fixed location on earth, such a satellite would appear to move in a figure of eight pattern.

Figure 1.1.2 : Geostationary and Geosynchronous A precise geostationary orbit cannot be attained in practice due to disturbance forces in space and gravitational effects of the earth, moon and sun. These forces cause a drift in latitude. The earth’s equatorial ellipticity causes the satellite to drift eastward along the orbit to one of the stable points at 75 E or 105 W. In practice, station-keeping maneuvers have to be performed quite frequently to correct for these shifts. Thus the key command and control earth stations must have tracking facilities. Typically the satellite is maintained within 0.1  in the C band and 0.05  in the Ku band, in both latitude (north south) and longitude (east west).

1.2 ORBITAL ALTERNATIVES

Fig 1.2.1 : Different orbits in solar system 1.1.2 LOW EARTH ORBITS – LEOs Low Earth Orbit (LEOs) satellites are very different from geostationary satellites in that they do not stay in a fixed position over the earth. Further, LEOs inhabit an orbital altitude between 450 km to 1000 km above the earth. This offers advantages and disadvantages. The advantages include a much shorter signal time delay (5 - 10msec), much lower-power transmitters are required, and the launch costs are reduced. There are a number of disadvantages as well. The first is that the satellite moves so quickly that it presents a moving target to a ground terminal. This also means that a given satellite will be visible over a given target for only a few minutes. The majority of LEO networks in the planning stages are focused on the mobile wireless telephony market and/or data communications. Some also plan to offer video, paging, and fax capabilities as well. Some will attempt to serve niche markets, such as email and short message services.

1.1.3 MEDIUM EARTH ORBITS – MEOs Medium earth orbit (MEOs) satellites are also different from geostationary satellites. They do not stay in a fixed position over the earth. MEOs inhabit a higher orbital altitude than LEOS, approximately 15,000 km above the earth. Because of their relatively high earth orbit, MEO networks only require about a dozen satellites to ensure worldwide coverage and full, uninterrupted operation. The first MEO system is expected to provide voice, data, fax, and short message services.

1.3

FREQUENCY BANDS

The frequencies currently available for communications satellites are limited, at best. Communications satellites have been assigned four distinct bands for transmission – see table 1 below. These include the C frequency band, Ku/K frequency band, Ka frequency band, and the X frequency band. (The government and military telecommunications satellites, exclusively use the X frequency band.) Satellites are required to share the relatively low frequency C band with terrestrial microwave deployed by common carriers. Further, the bandwidth available is not the most desirable for telecommunications satellites (the most desirable C band frequencies, to mitigate the effects of rain attenuation and absorption, would be from 4GHz to 6GHz). Since the band frequencies available are to be shared, careful planning is required to assure that interference is minimized. The FCC and INTELSAT closely monitor this issue. Close coordination of antenna spacing and positioning helps to lessen interference between satellite and terrestrial microwave transmissions. An additional precaution to minimize signal disruption is to utilize highly focused directional antennae.

1.4 SATELLITE DESIGN : In general, a satellite system has five major components. There are the two satellite links, i.e., the uplink and the downlink, to and from the satellite. There are also two terrestrial links, connecting the two earth stations with the user sites.

Figure 1.4 : Satellite Link – Major Components Finally, there is a satellite repeater, used to amplify and repeat signals. The satellite itself has five major components, (1) the transponder, (2) the on-board power supply, (3) the attitude control apparatus, (4) telemetry equipment, and (5) station-keeping apparatus.

Fig 1.4.1 Satellite Transponder The transponder is the on-board relay station for the satellite. Its function is similar to that of a terrestrial microwave radio relay station. It has both receiving and transmitting antennae; associated with the receiving antenna is a low noise amplifier

(LNA), which is used to improve the received signal without adding any noise. The signal is then passed to a frequency converter, which converts the received signal to a predetermined downlink frequency. It is then passed to a high-powered output amplifier, which boosts the downlink signal and sends it to the transmitting antenna. The on-board power supply is typically a series of solar batteries; power conservation is achieved by turning off equipment when not in use. This is done from earth, using monitoring equipment that sends appropriate instructions based on functions required on-board the vehicle. Solar battery life is the primary determining factor in the useful life of a satellite. Once the on-board power supply in exhausted, the satellite becomes just another piece of useless space junk. Storage batteries are also provided to maintain services during the eclipses, which occur around the spring and autumn equinox. The attitude of a satellite refers to its orientation in space. The attitude control apparatus is one of the most important pieces of equipment on-board. It prevents the satellite from spinning out of control in space and that the directional antennas point in the proper direction. This can be done in one of two ways: (1) spin stabilization, or (2) three-axis stabilization. Spin stabilization involves rotating a satellite on its axis at about one hundred revolutions per minute (100 rpm) and providing constant positioning and polarization toward earth and is nor used with cylindrical satellites. Three-axis stabilization involves the use of an on-board gyroscope and positioning thrusters to regularly adjust the satellite's attitude. Attitude control must not be confused with station keeping, which is the term used for maintaining a satellite in a correct orbital position, although the two are closely related.

1.5 EARTH STATION TECHNOLOGIES : The advantage of satellite technology is based on the potential for reaching wide expanses and serving discontinuous user bases without the cost of traditional terrestrial services (i.e., multiple central offices, microwave hops, repeaters, etc). Therefore, the

earth station becomes a critical factor in the design of satellite systems. Technological advances in the area of earth station equipment improvement has been a continuing focus for satellite system manufacturers. The more technology can be improved and costs reduced, the greater the potential for the future of satellite communications. There are currently three classes of earth stations: Mass capacity station--Designed for large users or inter-exchange carrier applications. This type of earth station serves a user community with communications needs great enough to require feeder line access to the earth station. The cost for earth stations in this class runs into millions of dollars. Middle range earth station--Designed for large corporate applications. This type of earth station serves a single large user (e.g. newspaper publisher, financial institution, etc). The cost for earth stations in this class run into the hundreds of thousands of dollars. Low-end earth station--Designed for smaller corporate applications. This type of earth station serves a single user (e.g., retailers, general business, etc) and is typically designed to handle data traffic (e.g., point-of-sale information, inventory control, credit authorization, and other types of remote processing). These types of earth stations are established with a minimal amount of equipment and a very small aperture terminal (VSAT). Each VSAT site is equipped with a terminal consisting of an antenna (varying in size from 1.2 to 1.8 meters in diameter), outdoor electronics mounted on or near the antenna (for signal reception and transmission), and indoor electronics for connection to the customer's local area network, CPU, telephone equipment or video equipment. The cost for earth stations in this class runs approximately $10,000 or less. Because of the low cost, the users of VSAT technology can take advantage of the basic nature of satellite communications (i.e., broadcast), and have the flexibility of moving or adding sites without tremendous added expense. The savings achieved using VSAT networks have been quoted as high as 50 percent over the cost of traditional leased lines from a carrier.

1.6 Problems in sattelite communication Transmission problems : HEAVY RAINFALL 

Signal attenuation



Attenuation higher at high frequency



Alters the polrasition

2.0 NETWORKS: 2.1 RADIO NETWORK •

Key Distribution Infrastructure.

•

SCPC Audio & / or Data Network

•

Audio MPEG-1, LII Encoding

•

Audio program distribution for Recording OR Local transmission

2.2 CES NETWORK: •

BROADCAST Network

•

Captive Earth Stations (CES) uplinks radio programs.

•

RN Terminals at AIR stations receive down linked Radio programs

•

Uses INSAT series of satellite

•

Distribuiton all over india possible

•

RN Network consists many UPLINK Earth Stations

•

Caters to the Regional Audio program distribution

CES SYSTEM REGION - A

N IO EG

CES NETWORK

R

CES SYSTEM REGION-C

-D

R

EG

IO

N -C

CES SYSTEM REGION-B

RN TERMINALS

CES SYSTEM REGION-D

Fig 2.1 : Block diagram of CES network

2.3

RN CHANNELS AT DELHI STATION

•

8 channels on c×s (analog transponder)

•

14 channels on c×c (digital transponder)

•

Carry 33 different services

•

Carry 19 different national/regional programmes

2.4 Introduction to Subsystems 2.4.1CAPTIVE EARTH STATION- UPLINK

Rf dri ve r

ANALOG MOD

D I V I D E R

1:1SW

ANALOG MOD.

IF PP

UPCONV

HPA

ANALOG MOD.

4:1

1:1SW

COMB

1:1SW

1:1SW

ANALOG MOD.

1

ENCODER-1

8

1 AUDIO SW

ENCODER-8 8

SPARE ENCODER

DIGITAL MOD-1

DIGITAL MOD-8

UPCONV

8:1SW

SPARE DIGITAL MOD.

Fig 2.4.1 : Uplink base device set up diagram

HPA

MCU

ACU

2.4.2 CAPTIVE EARTH STATION- DOWNLINK

DIGITAL RECEIVER-1

DIGITAL

AUDIO OUTPUT MONITORING FACILITY

RECEIVER-2

DIGITAL RECEIVER-7

1:8

L-BAND

1:2

DIGITAL RECEIVER-8

ANALOG RECEIVER-1

ANALOG

1:2

RECEIVER-2

Fig 2.4.2 : Down link set up diagram

schematic diagram of uplink/downlink setup at CES

UPCONVERTER

Fig :2.5.5 : kit of up converter •

70 / 140 MHz IF INTERFACE, 50 / 75 .

•

2140MHz IF FOR 72MHz TRANSPONDER(KU BAND)

•

DOUBLE CONVERSION DESIGNS COMMON.

•

In built switch in primary upconverter.

•

PHASE

NOISE

PERFORMANCE

AS

PER

IESS

PERFORMANCE MUST EXCEED THIS BY ATLEAST 6dB.

Fig :kit of digital modulator

308.

UNIT’S

ENCODER The encoder is a digital device used to encode the appropriate data (digital data ) At the transmitting end. This support the multiplexed data unlike in case of analog communication.

Fig :Encoder kit diagram

OUTSIDE BROADCASTING

INTRODUCTION Outside Broadcasts (abbreviated as OBs) form a substantial portion of programmes radiated from a Radio Station. Major events that occur at different parts of a country, such as sports events, important functions of political, cultural and national important and other such programmes that originate from outside the broadcast studio are covered as OBs. Different Types of OBs OBs can be classified into two types : i)

Live Broadcast

Events of national importance such as Independence Day Celebrations, sports events etc. are generally radiated as Live programme. ii)

Spot Recordings

Most of the OB programmes are recorded at the OB spot with the help of a portable, battery operated OB amplifier and or an Ultra Portable Tape Recorder (UPTR) or a cassette tape recorder. Some programmes, depending on their importance are recorded at the studio end. In this case, it is necessary to book telephone lines, from the OB spot to CR. Normally three such lines are booked. One for feeding the programme to CR, one for inter communication between the OB spot and CR using a magneto telephone, and one as a standby programme line. Equipments Normally used in OBs i)

OB Amplifier

An OB amplifier is a portable mixing unit. Normally four low level microphone inputs and one high level input from a PTR or UPTR, can be mixed and controlled by this unit. The individual channel output levels as well as the level of the programme after mixing can be controlled by rotary step attenuators.

A tone generator providing three spot frequencies (75 Hz, 750 Hz or 1 kHz, 7.5 kHz) is incorporated in this unit so that the frequency response of the telephone line on which the programme is fed can be quickly checked at CR end and equalisation done, if found necessary. The auxiliary output can be used for random operation or for feeding a public address system. Thus two OB amplifiers can be cascaded, and nine programme sources can be controlled. A portable mixer has recently been developed by M/s Meltron which can be used with Nagra or Meltron UPTRs. This mixer enables use of three microphones and has a high level input. The main feature of this mixer is that it is of light weight and takes power supply from UPTR itself. ii)

Microphones

The choice of the correct type of microphone and its proper handling and placement is very important for the success of an OB. The microphones used in OBs must be robust, insensitive to wind noise and popping effects, and having a good front to back ratio to avoid feedback. Hence, when choosing a microphone, for OB operations the directional characteristics of the microphones should be considered carefully. Suitability of different microphones for OB recording is discussed below. Omni directional Microphones Omni-directional microphones are sensitive to sound from all directions equally and hence they are preferred in studio recordings. But dynamic cardiod microphones are better suited for OB recordings.

Short Gun Microphones In OB situations such as cricket test match or athletics coverages, the sound is to be picked up from a distance and hence we require a microphone with a narrow acceptance angle. Gun microphones are used on such occasions. Its constructional structure is such that all sounds other than those from the wanted direction, arrive in such a manner as to produce a very low output from the microphone. Hence, shot-gun microphones are used when the microphone must remain at some distance from the sound or good rejection of sound from the sides and rear is desired. Radio/Wireless Microphones In sports coverages, there may be situations such as in a big stadium where different athletic events take place simultaneously where it is not possible to lay cables.Radio microphones are best suited for these locations.In a radio microphone, the microphone is connected to a miniature FM transmitter (held in hand) and the audio is picked up from the demodulator output of a FM receiver. Such radio microphones are used in locations where long cable distances are involved or where it is not possible to lay the cable. Use of Wind shields When microphones are used out of doors, in windly conditions, wind shields are used. But wind shields tend to have adverse effect upon the frequency and directional response of the microphones.

Hence, they should be selected with care, and used only when

necessary and suitable corrections are to be made to the frequency response and operational techniques.

iii)

Tape Recorders

Spot interview and glimpses of the various events taking place in a particular city, are covered by spot recordings done with Ultra Portable Tape Recorders (UPTRs) and cassette tape recorders. They are light weight battery operated recorders and are provided with only headphone monitoring facility in order to avoid the drain on the batteries. Generally two sets of either dry cells or chargeable cells are taken for the OB recordings, so that atleast 30 minutes of recorded programme is made feasible. Major studio centres such as the BH, New Delhi are provided with a number of such UPTR s and cassette tape recorders so that more than twenty different event can be covered with the help of such UPTR s. The recorded tapes are brought back to the BH, and a composite news capsule is made with the help of console tape recorders, in the dubbing room. The edited programme is used in the programmes such as Radio News Reel, Agricultural Programmes, special features etc. Important Guidelines for coverage of OB s Cassette tape recorders in our network are not of uniform quality. Each cassette recorder should be thoroughly tested for satisfactory quality before sending it for OB recording. For VIP recordings, Portable tape Recorders (PTRs) are used. A PTR is mains operated, provides good quality and is also sturdy enough to withstand continuous operation. PTRs can also be taken to those OB spots where AC power supply is available. It is preferable to take a variance to take care of power supply voltage fluctuations. OB Van AIR has acquired a few OB Vans recently. The vans are of the size of a matador vehicle and incorporate equipment of latest technology. Each van has been provided with a 6 channel audio mixer 3 UPTRs and a Public Address Amplifier.The interior is acoustically treated and air-conditioned. A portable diesel generator can be housed in the body. It is

possible to record talks and interview inside the van. All microphones inputs are terminated on a panel and cable drums provided for laying of the cables for recording the outside programmes and placement of effects mikes in the field. Provision is available to meet most of the requirements of production, recording, editing and dubbing etc. The van can also meet the requirements of a live coverage. Provision will be kept for installing a VHF/FM transmitter and a video camera along with a monitor inside the van in case these are required for certain types of coverage.

SUMMARY AND CONCLUSION In this sector of training I studied about the overall procedure and objective of the Broadcasting process in elaborate form. All India Radio had provided us all the equipments and apparatus for understanding us the each and every section up to its depth. I visited the various sections like server and networking room, lines room, control booth, captive earth station etc. After studying these sections I get understood their execution and importance for the transmission and reception of the data in All India radio. The training started was with the server and networking room where I visited and studied about the overall networking procedure and the interconnection between the servers to access the private data as well as public data. The data like news , audio songs etc are available to every server at any instance in any section. Every server is independent to fetch and add the data to them. The servers are connected to each other via bus topology and Ring topology. The next section was Lines room including all the lines containing data decoding and arriving at same room and can be accessed. This data can be further forwarded to the other studios and control room with help of Encoder. These data can also send through the telephone lines in then form of Analog data., and further can be receive in the digital form. In control booth section the overall control of the signals taken in the consideration., with the help of new technologies and various amplifiers. In the Captive Earth Station I learned the reception and transmission of data in the form of signals via two types of channels cxc and cxs channel an digital and analog form. Satellite communication is general and very important in todays life., because today human growth and development in the communication field is only because of the credit satellite communication. I studied the whole All India Radio broadcasting process with full of attention and enthusiasm.