Industrial visit report all india radio and toshniwal industries
Industrial Tour Report on
All India Radio Ajmer
Toshniwal Industries pvt. Ltd.
In partial fulfillment
For the award of the Degree of
Bachelor of Technology
In Department of Electronics and Communication Engineering
Dr. Rekha Mehra
Manish kumar sharma
Head of Department
Electronics and Communication
Department of Electronics and Communication Engineering
GOVT ENGINEERING COLLEGE AJMER
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
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.
TABLE OF CONTENTS
Table of Contents
List of Figures
List of Tables
TOSHNIWAL: AN INTRODUCTION
Decade Resistance Box
High Power Transmitter
ATU Mast and Arial
Radio Networking Terminal
Transmitter Salient Feature
PARALLEL OPERATION OF TRANSMITTERS
Need for Parallel Operation
Procedure for Tuning and Combining
Methods of Earthing
Measurement of Earth Resistance
LIST OF FIGURE
Decade Resistance Box
CT and PT
OCB and ACB
Parabolic Dish Antenna
Series to Parellel Conversion
Antenna and Guy Wire Insulator
Earth Electrode Resistor
LIST OF TABLES
Transmitter Salient Features
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.
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
2.1 OPTICAL PYROMETER
Fig.2.1 Optical Pyrometer
The Partial Radiation Pyrometer, ‘PYROPTO’ is a disappearing filament Optical Pyrometer,
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.
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.
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
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
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:
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
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
2.6.1 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.
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
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.
ALL INDIA RADIO: AN 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
All India Radio is also known as Akashvani. The head quarter is at the Akashvani Bhavan, New
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
Fig.3.1 AIR Logo
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
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.
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
b) By Population
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
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
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
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
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
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
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
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:
From the two incoming feeder lines, one of them is selected using the G.O.Switch.
The incoming high voltage (11 KV) is stepped down to 110 V using a Potential
The Current Transformer further reduces the current from 40 A to 5 A.
Further the two incoming feeder lines are interlocked mechanically using Kassel key.
Oil Circuit Breakers are used in it.
There are various sources of programs in Akashvani Ajmer.
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
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.
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. 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
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)
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.
5.3 TRANSMITTER SALIENT FEATURES:-
Table no. 5.1
BEL HMB 140
MAST base Impedance
2386565 Sq.mt, 140 BIGHA
05:55 – 09.30
Two 11kv overhead feeder from
MADAR and GAGWANA
Standby Power Supply
2*400KVA 3ph Alternator Kirloskar
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.
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
The phase of the signal of the transmitters depends upon the tuning stages which employ active
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
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
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.
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
Rp Rs 1 Xs / Rs 2
Xp Xs 1 Rs / Xs2 ,
1 Rp / Xp2
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.
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
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.
ANTENNA TUNING UNIT
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.
Fig.7.1 Antenna and guy wire insulator
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
It is for ensuring that no current carrying conductor rises to a potential with respect to
general mass of earth than its designed insulation.
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 :
Pipe Earthing (Fig. 1)
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.
Then earth resistance R =
Voltage drop between E and B
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
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.
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.
 Electronics Measurements and Instruments A.K. Sawhney
 Electronic Communication systems in advance by Wayne Tomasi
 Taub’s Principles of communication by Herbert Taub, Donald L Schilling