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    Industrial visit report all india radio and toshniwal industries Industrial visit report all india radio and toshniwal industries Document Transcript

    • An Industrial Tour Report on Industrial visit At All India Radio Ajmer And Toshniwal Industries pvt. Ltd. Submitted In partial fulfillment For the award of the Degree of Bachelor of Technology In Department of Electronics and Communication Engineering Submitted To: Submitted By: Dr. Rekha Mehra Manish kumar sharma Head of Department 10EEAEC041 Electronics and Communication Department of Electronics and Communication Engineering GOVT ENGINEERING COLLEGE AJMER January 2014
    • ACKNOWLEDGEMENT It was not possible to prepare this industrial tour report without the assistance and guidance of other people. On the very outset of this report, I would like to extend my sincere and heartfelt obligation towards all the personages who have helped me in this endeavor. I am ineffably indebted to our principal, the head of department and teachers who infused me with the spirit to work upon challenging field which has its inception in such a time when there is a dire need for new orientation. I am thankful to the management of All India Radio, Ajmer and Toshniwal Industries Pvt. Ltd. for allowing us to take tour in their concern. I am greatly indebted to our supervisor Mr. Harish Sharma and Mr. Sunil Sharma who conceived detailed and superior guidance throughout our tour. Without their ungrudging cooperation it would not have been possible to complete this training. Last but not the least; our efforts could never meet this success without the blessing of God and our families. We can never think of repaying their affection, care and encouragement without which it would have been difficult to reach the shores. Manish kumar Sharma 10EEAEC041 VII SEM i
    • ABSTRACT Toshniwal Industries Pvt Ltd. (TIPL), an ISO 9001:2000 certified company is a Private Limited company incorporated in 1959 at Mumbai. The company was set-up under the aegis of Toshniwal Brothers Pvt. Ltd. (Estb. 1948) under the guidance of its founding Chairman & Managing Director, (Late) Dr. G.R. Toshniwal, and D. Sc. In a short span of time, TIPL was recognized as a leading instrumentation company in India as a manufacturer of quality instruments and excellent services to customers. Prasar Bharti is a statutory autonomous body established under the Prasar Bharti Act and came into existence on 23.11.1997. It is the Public Service Broadcaster of the country. All India Radio (AIR), is the radio broadcaster of India and a division of Prasar Bharti (Broadcasting Cooperation of India), it is the sister service of Prasar Bharti’sDoordarshan. Report includes the description of all the departments of All India Radio, Ajmer. First block includes the power supply arrangements of Akashvani. AIR Ajmer derives power supply of 11kVA from two sources (one at a time):1. Madar Feeder 2. Gagvana Feeder AIR Ajmer has two 100kW transmitters connected in parallel. Combined output is of 200kW. Each transmitter section includes the RF and AF chains and the circuits for removing harmonics. Audio signal is obtained from Jaipur studio through C-Band. S-Band is used for reception of short wave signals transmitted from Delhi and other capital stations. The most important one was the mast/antenna along with the antenna tuning unit. ATU is used for impedance matching purpose. Antenna used here is of BEL HMB 120. Its physical height is of 200 m while electrical height is 248m. It is a self-radiating antenna. Next we studied the concepts of satellite communication. ii
    • TABLE OF CONTENTS CHAPTER CONTENTS No. PAGE No. Cover page Acknowledgement i Abstract ii iii-iv Table of Contents List of Figures v List of Tables vi 1. TOSHNIWAL: AN INTRODUCTION 1-2 2. PRODUCTS 3-9 2.1 Optical Pyrometer 3 2.2 Thermal Imager 4 2.3 Rheostat 4 2.4 Decade Resistance Box 6 2.5 RTD 6 2.6 Thermocouple 7 2.6.1 Ceremic Beaded 7 2.6.2 Mineral Insulated 7 2.7 8 2.8 3. IR Thermometer Kelvin Bridge 9 AIR:INTRODUCTION 10-11 3.1 Introduction 10 3.2 High Power Transmitter 11 iii
    • 3.3 11 3.4 Land 11 3.5 Power Supply 11 3.6 5. ATU Mast and Arial Broadcast Area 11 SATELLITE COMMUNICATION 17-21 5.1 Satellites 17 5.2 Radio Networking Terminal 18 4.2.1 4.2.2 5.3 6. Outdoor unit 18 Indoor unit 21 Transmitter Salient Feature PARALLEL OPERATION OF TRANSMITTERS 22-24 6.1 Need for Parallel Operation 22 6.2 Requirements 22 6.3 Procedure for Tuning and Combining 24 7. ATU 25-26 8. EARTHING SYSTEM 27-30 8.1 Earthing 27 8.2 Methods of Earthing 27 8.3 Measurement of Earth Resistance 27 CONCLUSION 30 REFERENCES 31 iv
    • LIST OF FIGURE FIGURE No. TITLE PAGE No. 1.1 TIPL Logo 2 2.1 Optical Pyrometer 3 2.2 Thermal Imager 4 2.3 Rheosast 4 2.4 Decade Resistance Box 6 2.5 RTD 6 2.7 IR Thermometer 8 2.8 Kelvin Bridge 9 3.1 AIR Logo 10 4.1 CT and PT 12 4.2 ACB 14 4.3 OCB 14 4.4 OCB and ACB 15 4.5 Transformer Setup 16 5.1 Satellite Communication 18 5.3 Parabolic Dish Antenna 20 6.1 Bridge T-Network 23 6.2 Series to Parellel Conversion 23 7.1 Antenna and Guy Wire Insulator 26 8.1 Earth Electrode Resistor 29 8.2 Earth Tester 29 v
    • LIST OF TABLES TABLE No. 5.1 TITLE Transmitter Salient Features PAGE No. 21 vi
    • Chapter.1 TOSHNIWAL INDUSTRIES PVT. LTD.: INTRODUCTION Manufacturing commenced in a spacious factory setup at Ajmer in 1963 in technical collaboration with world leading instrumentation companies like Hartmann & Braun, Germany; British Electric Co. Ltd., UK; W.G. Pye & Co., UK. After completion of the term of these collaboration agreements, TIPL continues to manufacture instruments as per the technical know-how received. Many of the instruments, as per the collaborator’s designs, have been updated with the efforts of their in-house R&D. Since 1984, TIPL has taken up the marketing of various related product lines from renowned manufacturers from Japan, USA, UK & Germany and provide complete application engineering, installation & commissioning and after sales service support to customers. Mr. M.G. Toshniwal, Chairman and Mr. Rajeev Toshniwal, Managing Director of TIPL have a long experience of managing medium size engineering industry and are supported by a team of professionals. TIPL owes its technological leadership to its engineers and business managers backed by a dedicated work force. TIPL has modern facilities for manufacturing. It has world-class test & measuring instruments to ensure accuracy of manufacturing and calibration and for quality assurance. It has Black Body Radiation Calibration Furnaces for calibration of Infrared Radiation Thermometers. It maintains traceability National Physical Laboratory, Delhi and can provide calibration and accuracy certification as per ISO 9000 requirements. TIPL has a fully equipped R&D Department from the very beginning. Since 1974, it is recognized by the Dept. of Science & Technology, Govt. of India as a R&D Unit for Industrial Developments. R&D is equipped as per international & Indian standards, specifications and is engaged in development of new electronic instruments and process control systems. TIPL introduced many new instruments, incorporating the latest technologies and electronics to meet the changing and demanding industrial requirements. 1
    • TIPL product range includes Thermocouples, RTDs, Thermo wells; 2 wire and 4 wire Temperature Transmitters; Digital Indicators, Controllers; Reference Junction Compensators; Selector Switches; Optical Pyrometers; Signal Converters; I/P Converters; Signal Conditioners; Test & measuring Instruments etc. TIPL also markets Portable Infrared Thermometers and Thermal Imagers (Fluke, USA); Portable and On-line Infrared Thermometers, Line Scanners and Systems (Raytek, USA); High Temperature Video Imaging Systems (Imaging & Sensing Technology, USA); Microprocessor based Hybrid Recorders, PID Controllers, Program Controllers (Ohkura Electric, Japan); Paperless Recorders (Envada, U.K.); Electronic Ear for Ball Mill Optimization Systems, Solid Flow Measurement and Control Systems (Sankyo Pio-Tech Co. Ltd., Japan); Sensors & Systems for Combustion Engineering (Lamtec, Germany); General Surveillance and Plant/ Process Monitoring CCTV Systems (Pelco, USA); IT solution for Cement Plants (Powitec, Germany); Ball Mill Optimization Systems (Kima, Germany) etc. TIPL’s major customers are iron & steel industries; cement plants; glass and ceramic industries; pulp & paper industries; furnace, thermal & nuclear power plants; chemicals, petrochemical industries and refineries; engineering industries etc. TIPL also exports to the neighboring countries like Sri Lanka, Bangladesh, Nepal, Thailand, UAE and East African countries. TIPL has done installation and commissioning of instruments and control systems in these industries through their team of experienced engineers for supervision of installation and commissioning of instruments, control systems and CCTV systems. Many of the new projects in India have availed their services for project engineering to their satisfaction. Fig.1.1 Toshniwal Logo 2
    • CHAPTER.2 PRODUCTS 2.1 OPTICAL PYROMETER Fig.2.1 Optical Pyrometer The Partial Radiation Pyrometer, ‘PYROPTO’ is a disappearing filament Optical Pyrometer, suitable For measuring high temperature of incandescent objects, in annealing and hardening furnaces, in firing kilns, for measuring the temperature of molten and flowing metal or glass as well as incandescent blocks during forging, pressing or rolling. The temperature measurement makes use of comparison between the brightness of an electrically heated and calibrated incandescent filament(reference light bulb) in Pyropto and that of the object to be measured. The special advantage offered by the PYROPTO is the light weight of the instrument which houses all components of the complete measuring equipment. Thus, it can be transported by means of carrying strap from place to place without any inconvenience. Due to its appropriate design, the simple measuring principle used is the convenience of its operation. High accuracy measurements can also be carried out even by less skilled operators. An additional advantage is the suitability for carrying out measurements on very small surfaces of down to 2 mm diameter and a measuring distance of 60 cm. Every PYROPTO has two measuring ranges. 3
    • 2.2 THERMAL IMAGER Fig.2.2 Thermal Imager The Fluke TiR4FT, Tir3FT and Tir2FT IR Flex Cam Thermal Imagers are for professionals demanding the best and most thorough solution in building diagnostics applications. Fluke TiR Series Thermal Imagers are built specifically for the building diagnostic industry. Property managers and facility managers use thermal imaging to protect investments and keep buildings in a well maintained, healthy state. Restoration professionals are using thermal imaging to increase their business, differentiate themselves from their competitors and generate documentation in case they need to defend a future liability claim. 2.3 RHEOSTATS FIGURE 2.3 4
    • Rheostats are mainly used for regulating electric current in industry and laboratory where these are used as adjustable resistors in electrical circuits. With three terminal provisions, these can be used to vary a D C potential smoothly from zero to maximum. Toshniwal Rheostats consist of resistance wire wound on a former which is made from solid drawn hexagonal steel tube vitreous enameled, ensuring good mechanical strength and sturdiness. The tube is fitted in two end castings insulated with micanite cups. The Brush gear slides on a highly polished square slide rod. The brush is of copper graphite with pigtail connections. Two heat resisting compression spring hold brush family in contact with the resistance wires. Copper graphite brush provides necessary lubrication to prevent wear and tear of wire even at elevated temperatures. The brush is housed in a slider knob of molded Bakelite designed for easy handling. Different designs in a single tube and double tube models are available to meet with demands of different applications. In many applications larger values of resistance are required to be accommodated in small space but at the same time the current rating desired varies for lower to the higher values of resistance. For such requirements Rheostats are also available in space saving graded winding designs. For requirement of graded Rheostats desired resistance, voltage, maximum and reduced current rating should be stated. Lead screw type Rheostats are also available for precision and smooth setting of brush position using hand wheel provided axially or at right angles to the lead screw which replaces the slide shaft in this design. The temperature rise above ambient temperature is with Rheostats mounted vertically in free air, with hotter end of the winding above the brush. The above current ratings are continuous and are based on the tube being mounted vertically in free air are with the hot portion of the winding above the brush. Should it be necessary to mount the tubes horizontally, the current should be reduced to 75% of the rated value. Ohms values for double tube are with both tubes connected in series.Ordering Data: 5
    • When placing order, please mention Cat. No. tube size & length in inches, current & ohms rating. Example: PL 12.01, 2” X 12”, 5A/25 Ohms. 2.4 DECADE RESISTANCE BOX Fig.2.4 Decade Resistance Box Positions in addition to zero position. Specially designed switch with self-cleaning and silver plated contacts ensure very low contact resistance and long life. Resistances of 10 k ohms & lower are made of non-inductively wound selected manganin. Coils are heat treated and aged for long term stability. 100k and 1M ohm decades have selected & precision metal film resistors of very low temperature co-efficient. All the decades are housed in metallic/wooden rugged casing and are provided with knobs having ribs for comfortable operation. Decade Resistance Boxes are available with 4, 6, 7 & 8 decades and offer a wide choice of resistances to meet with almost every requirement in industry & laboratories. 2.5 RESISTANCE TEMPERATURE DETECTORS Fig.2.5 RTD 6
    • For temperature measurement in the range, -200°C to + 850°C Resistance Temperature Detector (RTD) is preferred to Thermocouple and other sensors because of its higher accuracy, reliability, compact size and faster response. RTDs find use in almost all industries like plastic and rubber processing, food industries, pharmaceuticals, chemical & petrochemical plants, and power plants. It is also used in diesel engines & ships, process control and laboratories for temperature measurement and control. RTDs are available with single or double resistance elements and in 2, 3 or 4 wire circuits. Various types of protection sheaths for protection of the element and screw-in threaded bushes either fixed (welded) or adjustable by screws (for non-pressure application) or by compression fitting (for pressure application) for mounting are available. RTD normally consists of spring-loaded insert, outer protecting sheath with mounting connections and cast aluminum terminal head. The insert assembly consists of Pt 100 element with silver/copper connection leads, insulated by ceramic multibore insulating tube/beads in a brass or stainless steel sheath with ceramic terminal block and brass terminals attached to a spring loaded arrangement 2.6 THERMOCOUPLE 2.6.1 CERAMIC BEADED A thermocouple consists of two dissimilar metallic Wires joined at one end known as hot junction. When the hot junction is heated, an emf is produced which depends on the difference between the temperature of the hot junction and the temperature of free ends known as cold junction. This thermo emf is measured by galvanometric/potentiometer metric/digital instruments, to display temperature. 2.6.2 MINERAL INSULATED Mineral Insulated Thermocouples & Resistance Temperature Detectors comprise of a metal sheath in which the thermo-electric elements/RTD element with conductors are embedded in highly compressed magnesium Oxide (MgO) insulation, thus providing the elements complete protection against oxidation and corrosion. Thermocouples are available in type K, J, T, E, R, S, W, W3 and W5, simplex or duplex, in sheath diameters from 1mm to 19.05mm and length from a few cm to 200 meters. 7
    • 2.7 IR THERMOMETER Fig.2.7 IR Thermometer The Fluke 62 Mini digital thermometer is the perfect introduction to infrared (IR) thermometers for the professional. The Fluke 62 Mini Infrared Thermometer offers quick and reliable surface temperature readings. This compact and portable IR thermometer enables technicians to diagnose heating and ventilation problems and monitor the temperature of electrical motors and electrical panels without contact. Rugged enough for industrial environments with its protective rubber “boot”, the Fluke 62 Mini Infrared thermometer also comes with a handy nylon belt holster to keep quick temperature checks at the ready. What are the benefits of using IR thermometers?    Effectively find your problems quickly and safely, saving time and cost IR thermometers are accurate, usually within one degree IR thermometers safely read hard-to-reach or inaccessible objects . 2.8 KELVIN BRIDGE This instrument employs the double Kelvin Bridge principle for accurate measurement of low resistances. Twin, 5-position ratio arm, combined with a decade & slide wire, provide a wide range of resistance measurement, i.e. 0.2 micro-ohms to 11 ohms with high accuracy. Two or four terminal measurements may be employed. Current up to 10 A can be used during measurement. 8
    • Fig.2.8 Kelvin Bridge All controls are simple to operate. Thermal emf. may be taken into account using the three position (Normal/Off/Reverse) current switch. Both ratio arms are operated by one switch. The press keys give full and reduced sensitivity control for the galvanometer detector. Readings are obtained direct from decade and slide wire scale multiplied by ratio arm switch setting. All dials, keys & terminals are positioned on an instrument panel mounted in polished wooden case with hinged lid. For measurement of resistance of thicker wires, strips and rods up to 15 mm dia, Conductor Clamps are also available. These Conductor Clamps have terminals for current as well as potential connections and are available for lengths of 100 cm and 50 cm. For convenience of operation, mains operated 10 A DC power supply Cat no.:PL39PS, power: 230V AC, 50 Hz is also available.  Especially suited for measuring low resistances.  Two or four terminal measurements can be performed.  Lead Balancing not necessary when lead resistances lie within specified limits. ACCURACY: ± 0.05 % or ± 1 slide wire scale division whichever is greater. 9
    • Chapter.3 ALL INDIA RADIO: AN INTRODUCTION 3.1 INTRODUCTION All India Radio (AIR) ,one of the largest radio networks in the world is a division of Prasar Bharti (Broadcasting Cooperation of India) currently working under the Chairmanship of Smt. MRINAL PANDEY and Shri JAWAHAR SIRCAR as its Chief Executive Officer Established in 1936, today it is the sister service of Prasar Bharti’s Doordarshan, the national television broadcaster. All India Radio is also known as Akashvani. The head quarter is at the Akashvani Bhavan, New Delhi. AIR today has a network of 237 broadcasting centers with 149 medium frequency (MW), 54 high frequency (SW) and 177 FM transmitters. The coverage is 91.85% of the area, serving 99.18% of the people in the largest democracy of the world. AIR covers 24 Languages and 146 dialects in home services. In External services, it covers 27 languages; 17 national and 10 foreign languages Fig.3.1 AIR Logo 10
    • 3.2 HIGH POWER TRANSMITTERS These stations are equipped with short wave/ medium wave transmitters together with extensive aerial system to serve the external, home and news services of All India Radio. The main function of these centers is to transmit the programs produced at nearby studios and also from Delhi studios. 3.3 ATU MAST AND AERIAL There is a 200 m height ECIL makes Self Radiating Guyed Mast. There are six numbers of Guys on different height segments of this mast. The feeder lines, ATU, mast and aerial field are being maintained in proper condition. There is a permanent security wall with fencing around the Transmitters Complex site .However, the Ariel field is separately fenced with security wall. 3.4 LAND The Transmitters Land comprising of 140 bigha (approx. 23, 86,560sq.ft) is on lease from Government for an amount of Rs.140/-annum. The land is on Jaipur-Ajmer national highway. 3.5 POWER SUPPLY There are 2 numbers of 11KV Overhead HT Feeders from Rajasthan state Electricity Board, namely Madar feeder and Gagwana feeder. These 11 KV overhead feeders comes to the G.O.SWITCH,LOCATED NEAR THE MAIN GATE OF Transmitting complex the HT metering panel is also located near this, and these are maintained by RSEB.From G.O.Switch the HT Power Supply comes to the 2 independent 11 KV OCB’s through underground cables. From these OCB’s the HT power supply is connected to the 2 nos.750KVA capacity HT transformers through independent isolators. Here it may be mentioned that at one time anyone OCB with the corresponding isolator can be connected to the 1HT transformer. 3.6 BROADCAST COVERAGE a) By area 91.42% b) By Population 99.13% 11
    • Chapter.4 POWER SUPPLY There are two 11KV Overhead HT Feeders from Rajasthan state Electricity Board, namely Madar feeder and Gagwana feeder. Various terms related to the Power Supply Arrangement are: 4.1 POTENTIAL TRANSFORMER (PT) The PT has large numbers of turns in primary and a small number of turns in secondary. It is connected across the line. Potential transformer is also used to step down from rated voltage/1.732 to 110volts/1.732. It is connected between phase and neutral. 4.2 CURRENT TRANSFORMER (CT) Current transformer is used for measuring and protection purpose. It is used to step down from rated current (40 A) to 5A. It is connected in series across conductors. The CT has a single turn primary and some few numbers of secondary turns, and it is ALWAYS kept short circuited. Using two CTs and PTs measurement of power in a three phase system can be obtained correctly. Fig.4.1 Current and Potential Transformer 12
    • 4.3 CIRCUIT BREAKER: The devices used for making and breaking an electrical circuit under some predetermined condition are called circuit breakers. The functions of a circuit breaker are as follows: 1. It must close on and carry full load currents for long period. 2. It must open automatically to disconnect the load, on over load under predetermined condition. 3. It must rapidly interrupt the heavy current, which may flow under a short circuit condition in any part of the system. 4. The circuit breaker must be capable of withstanding the effect of arcing at its contact and the thermal conditions, which arise due to flow of current. All circuit breakers consist essentially of pairs of matting contacts, each pair comprising fixed and moving elements. Under normal conditions, these elements are in contact and carrying full load current; but on receipt of a tripping signal initiated by hand or protective gear, the circuit will be interrupted. At the start of the separation, an arc will be established which is required to be extinguished as early as possible. Generally, we come across two types of circuit breakers at medium and high voltage, for indoor application. They are called Oil Circuit Breaker (OCB) and Air Circuit Breaker (ACB). 4.3.1 Air circuit breakers An air circuit breaker is that kind of circuit breaker which operates in air at atmospheric pressure. In air circuit breakers, the arc exists in the mixture of nitrogen, oxygen and metallic vapor and the successful arc interruption takes place due to cooling by diffusion. Rated current up to 10,000 A. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. Often used for main power distribution in large industrial plant. 13
    • Fig.4.2 Air circuit Breaker 4.3.2 Oil circuit breaker– In oil circuit breaker the fixed contact and moving contact are immerged inside the insulating oil. Whenever there is a separation of current carrying contacts in the oil, the arc is initialized at the moment of separation of contacts, and due to this arc the oil is vaporized and decomposed in mostly hydrogen gas and ultimately creates a hydrogen bubble around the arc. This highly compressed gas bubble around the arc prevents restriking of the arc after current reaches zero crossing of the cycle. Fig.4.3 Oil Circuit Breaker 14
    • Fig.4.4 OCB & ACB 4.4 LINE ISOLATOR: The line isolator is used to isolate any RF (common mode) that may have worked its way back to the station i.e. Keep that RF off of the outside of the transmission line and delivered to the antenna where it belongs. 4.5 POWER SUPPLY ARRANGEMENT DESCRIPTION: 1. From the two incoming feeder lines, one of them is selected using the G.O.Switch. 2. The incoming high voltage (11 KV) is stepped down to 110 V using a Potential Transformer (PT). 3. The Current Transformer further reduces the current from 40 A to 5 A. 4. Further the two incoming feeder lines are interlocked mechanically using Kassel key. Oil Circuit Breakers are used in it. 15
    • Fig.4.5 Transformer Setup 16
    • Chapter .5 SATELLITE COMMUNICATION There are various sources of programs in Akashvani Ajmer. 1. S-Band 2. C-Band 3. DTH Programs are recorded in Jaipur studio. These recorded programs were previously transmitted through Telephone lines. But these days S-Band and C-Band are generally used for transmission. 5.1 Satellites: Satellites are basically reflectors in sky. Satellite Communication is the outcome of the desire of man to achieve the concept of global village. Penetration of frequencies beyond 30 Mega Hertz through ionosphere force people to think that if an object (Reflector) could be placed in the space above ionosphere then it could be possible to use complete spectrum for communication purpose. 1st satellite named as “Sputnik -1” was launched in 1957 by USSR from Bikonour Cosmodromme in Kazakhstan. It was a low orbit passive satellite. It could only reflect the signals mechanically and could not receive, amplify, or change the frequency before transmission. In 1962 Telstar was launched from Cape Carnival by USA. It was also a low orbit satellite but active satellite. Due to following advantages satellite communication is generally used: - This is only means which can provide multi access two way communication. Within the coverage area, it is possible to establish one way or two way communication between any two points. - Satellites are capable of handling very high bandwidth. Normally any satellite can accommodate about 500 MHz in C Band. For example the bandwidth of INSAT-I is 480 MHz in C Band and 80 MHz in S Band. INSAT-II has a bandwidth of 720 MHz in C Band and 80 MHz in S Band. - It is possible to provide large coverage using satellite. For example geostationary satellite can cover about 42% of earth surface using global beam. 17
    • - It is easy and quicker to establish new satellite link using SNG terminal or VSAT terminal from any point to any other point as compared to any other means. Fig.5.1 Satellite Communication 5.2 Radio Networking Terminal The various All India Radio stations spread throughout the nation are required to relay certain programs which are originating from Delhi. Similarly there are certain programs which are originating from capital stations are relayed by the other stations in that region. In order to link Delhi and capital stations with other AIR stations, RN through INSAT is not only cost effective but also provide the good technical quality as compared to DOT lines and SW linkage. Thus RNT acts as the ground terminal for satellite signal reception. The block diagram of S-band RN terminal is shown in figure 4.1. The C-Band RNT has mainly two units: 1. Outdoor unit 2. Indoor unit. 5.2.1 Outdoor unit : Outdoor unit has mainly two components. a. PDA b. LNBC a. Parabolic Dish Antenna : PDA, 1.6 m Chicken mesh, is used to receive the downlink RF. The antenna assembly collects and concentrates RF transmitted signals that are produced by 18
    • communication satellite (INSAT 3C, 74’E) and converts them to an electronic signal. PDA is installed such that it receives maximum signal. It’s azimuthal (Az) and elevation angles (EL) are given by following formulas as viewed to INSAT 3C. EL = tan-1( cosD.cos ǿ - r/R ) ( 1 – (cosD.cos ǿ)2)1/2 AZ = 180˚± tan-1(tanD/sinǿ) Where, D = λr – λs in degrees λ r = longitude of the given λ s = longitude of the satellite r = Radius of earth = 6367 kms R = Radius of synchronous orbit = 42,165 kms ǿ = latitude of given site Coordinates of HPT Ajmer Latitude (ǿ) = 26˚31’07’’ Longitude (λr) = 74˚43’00’’ Longitude (λs) = 74˚ E EL = 59˚ AZ = 181.61˚ The RF signals gathered by the antenna (PDA) are forwarded on the feed horn, which collects the signals. The output of feed horn is then directed to the LNB down converter, which provides the initial amplification of the C-Band downlink signals and converts the C-Band signals to LBand. The output of LNB, down converter is routed to the IFL ( Interfaciality – Link ) cable (RG – 11) 19
    • Fig 5.3 Snapshot of PDA 5.2.2 Indoor unit : Indoor unit has mainly satellite digital audio receivers. The ABR202 receive L-Band RF and process it. After processing this satellite receiver provides analog L-R audio channels and digital audio output also. The receiver is also connected with computer by data port. This receiver chain is remotely controlled through computer command. It has mainly three indication in front panel, power, sync, enable. If the power is ok green indication will be displayed and if EB is greater than 7 sync will be locked and if EB is less than 4, receiver will not respond to the system. 20
    • 5.3 TRANSMITTER SALIENT FEATURES:- Table no. 5.1 S. No Property Description 1 Make/ Type BEL HMB 140 2 Radiated Power 2x100 KW 3 Frequency 603Khz 4 Wavelength 497.51 meters 5 MAST height 200 meters 6 Electrical Height 248 meters 7 MAST base Impedance 778+j50.30HMS 8 Site Area 2386565 Sq.mt, 140 BIGHA 9 Transmission Hours 05:55 – 09.30 12:00-15:00 17:00-23:10 10 Coverage AJMER-KOTA-JHALAWAR-UJJAIN 256Kms. AJMER-CHITTOR-UDAIPURBANSWARA 223Kms AJMER-SIKAR-CHURU-BIKANER 197Kms AJMER-JAIPUR-ALWAR-DELHI 215Kms. AJMER-PALI-JODHPUR-POKRAN 221Kms. 11 Power Supply Two 11kv overhead feeder from MADAR and GAGWANA 12 Standby Power Supply 2*400KVA 3ph Alternator Kirloskar 21
    • Chapter.6 PARALLEL OPERATION OF TRANSMITTERS 6.1 Need for Parallel Operation At times it may not be possible to get the required power from the single transmitter for the required coverage of the broadcast service. In such conditions, it is essential to combine two or more transmitters to get the required power. Besides combined operations also facilitate operation of single transmitter in case of failure of one transmitter thereby achieving reliability of the service. 6.2 Requirements Like parallel operation of alternators/generators there are three conditions to be satisfied for parallel operation of two transmitters. They are  Frequency of the transmitter should be the same.  The phase of the signal of the transmitters at combiner should be the same.  The power levels of both the transmitters should be such that the amplitude at the combiner is equal. In order to meet the first condition, it is possible to use one frequency source for both the transmitters. Hence if there is any drift in the frequency, it will be common to both the transmitters. The phase of the signal of the transmitters depends upon the tuning stages which employ active amplifiers. Such a network used for combining shall be such that it should  Should offer equal load impedance to both the transmitters.  Shall be able to continue the operation even if one of the transmitter goes off the air.  Shall facilitate to dissipate the unbalanced power flowing through the combiner network. The most common network which is used is a bridged “T” network. The figure 1 shows such a network. It has four reactive networks. Two capacitive and two inductive and all are having impedance’s equal to that of feeder line. These impedances can be interchanged as shown in 22
    • figure 6.1 (a) & (b). The bridged arm also has got one resistive load equal to feeder impedance. This shall take care of the unbalances in the network. (b) (a) Fig. 6.1 Bridged “T” Networks The break-up of impedances indicates how this network offers proper impedances to the transmitters at all possible conditions. Impedances can be converted into a parallel impedance and vice versa using the following formulae: -  Rp  Rs 1  Xs / Rs 2   Xp  Xs 1  Rs / Xs2 , Xs  Xp   1 Rs  Rp  1  Rp / Xp2    ,   1 1  Xp / Rp 2 Fig. 6.2 Series to Parallel conversion With the help of these equations we can break up the impedances as shown in figure 2. There are two cases of possibilities. They are I) both transmitters are working in combined mode ii) One of the transmitter failed in combined mode. 23 In the previous case we see that both
    • transmitters get proper load. And in the later condition, the transmitter in working condition gets proper load, but half the power is lost in combiner reject load. 6.3 Procedure for tuning and combining  Tune each arm of the network for impedance equal to load impedance.  Connect the network and terminate the load impedance.  Measure the load impedance offered at each of the transmitter. It should be equal to load impedance. If not adjust the reactance.  Open and short-circuit the output point of one of the transmitter (in off condition) and measure the load impedance at the other transmitter. It should not change.  Now put on the transmitters with a single oscillator source.  If there is unbalance try to adjust with the phase control of oscillator for minimum unbalance.  If the unbalance still persists try to adjust the power levels of the transmitters either by HT or AVR variations.  Modulate the transmitter slowly to see whether there is unbalance. If so check the audio phase to each of the transmitter. 24
    • Chapter.7 ANTENNA TUNING UNIT 7.1 Introduction Antenna Tuning Unit (ATU) is to match the feeder line impedance to the mast impedance of MW Transmitters for maximum transmission of power. So ATU is located between the mast base and the feeder line and is very close to the mast base. Commonly “Feeder Unit” which is located in the aerial field, houses the ATU. Generally the mast impedance (aerial impedance) is obtained in a complex form i.e. the real part (resistive) and the imaginary part (reactive) component. When the mast impedance is expressed in polar form then negative angle indicates the mast is capacitive and positive angle indicates the mast is inductive. Whether the mast impedance is inductive or capacitive depends on the height of the mast in terms of wave length (). If the height is less than /4, it will be capacitive and inductive if more than /4. This can be measured with impedance bridges. 25
    • 7.1 SNAPSHOTS Fig.7.1 Antenna and guy wire insulator 26
    • Chapter.8 EARTHING SYSTEM 8.1 Earthing Earthing is the connection of electrical equipment and wiring systems to the earth by a wire or other conductor. The primary purpose of grounding is to reduce the risk of serious electric shock from current leaking into uninsulated metal parts of an appliance, power tool, or other electrical device. In a properly grounded system, such leaking current (called fault current) is carried away harmlessly. Grounding is also used in manufacturing industries to prevent accumulation of hazardous static electrical charges. The function of earthing is two fold 1. It is for ensuring that no current carrying conductor rises to a potential with respect to general mass of earth than its designed insulation. 2. It is for the safety of the human beings from the electric shocks. 8.2 Methods of Earthing There are two popular methods of earthing : i) Pipe Earthing (Fig. 1) ii) Plate Earthing (Fig. 2) 8.3 Measurement of Earth Resistance The determination of resistance between the earthing electrode and the surrounding ground is of utmost importance. The resistance measurement is made by the potential fall method. The resistance area of an earth electrode is the area of soil around the electrode within which a voltage gradient measurable with commercial instrument exists. In Fig. 11.3 E is the earth electrode under test and A is an auxiliary earth electrode positioned so that two resistance areas do not overlap. B is a second auxiliary electrode placed half way between E and A. An alternating current of steady value is passed through the earth path from E to A and the voltage drop between E and B is measured. 27
    • Then earth resistance R = V/I V = Voltage drop between E and B I = Current through the earth path. To ensure that resistance areas do not overlap, the auxiliary electrode B is moved to positions B1& B2 respectively. If the resistance values determined are of approximately same magnitude in all the three cases, the mean of the three readings can be taken as the earth resistance of the earth electrode. Otherwise the auxiliary electrode A must be driven in at a point further away from E and the above test repeated until a group of three readings is obtained which are in good agreement. The use of alternating current source is necessary to eliminate electrolysis effects. The test can be performed with current at power frequency from a double wound transformer by means of a voltmeter and an ammeter or by means of an earth tester. The earth tester is a special type of meggar which sends AC through earth and DC through the measuring instruments. It has got four terminals P1, C1, P2 and C2 outside. The terminals P1, and C1 are shorted to form a common terminal which is connected to the earth electrode under test. The other two terminals C2 and P2 are connected to the auxiliary electrodes A and B respectively . For measurement of earth resistance two electrodes A and B are driven into the ground at a distance of 25 meters and 12.5 meters respectively from earth electrode E under test. The megger is placed on a horizontal firm stand free from surrounding magnetic field. The range switch is set to a suitable scale. The handle is then turned in proper direction at a slightly higher speed than rated one and the reading on the scale is noted. The three readings are taken for different distance. If they are practically the same, it is good otherwise average of these readings is taken as earth resistance. 28
    • Fig. 8.1 Testing of Earth Electrode Resistance Fig.8.2 Earth Tester 29
    • CONCLUSION This industrial visit enables us to enlarge our technical vision in such a way so that we can apply our subject matters into real time products. We excited a lot and a lot when we came to know about the achievements and projects of TIPL and AIR. Thus in our Industrial Visit to Toshniwal Industries Pvt. Ltd.,Ajmer we learnt about the manufacturing and functioning of various temperature sensing devices. We learned about signal processing and its propagation in AIR. 30
    • REFERENCES [1] http://prasarbharati.gov.in [2] http://en.wikipedia.org/wiki/Mast_radiator [3] http://en.wikipedia.org/wiki/Antenna_(radio) [4] www.allindiaradio.org [5] http://india.gov.in/knowindia/radio.php [6] Electronics Measurements and Instruments A.K. Sawhney [7] Electronic Communication systems in advance by Wayne Tomasi [8] Taub’s Principles of communication by Herbert Taub, Donald L Schilling [9] www.howstuffworks.com 31