Radar and its types

TYPES OF RADARS

A variety of radars have been developed and they are classified based on
1. The signal transmitted.
2. The target of interest and
3. The frequency of operation.

Some of the commonly used radars are discussed as follows.

CONTIUOUS WAVE (CW) RADAR

The radar transmitter transmits a continuous signal rather than a pulse one. The echo signal can be easily distinguished from the transmitted signal as there will be a shift in the frequency of the echo signal due to the DOPPLER EFFECT. Also, the echo signal’s strength is many times lower than the transmitted signal strength.
Using a CW radar, the relative velocity of a target can be determined. The drawback of a CW radar is that the range of the target cannot be determined.

MOVING TARGET INDICATION (MTI) RADAR

The MTI radar transmits a train of electromagnetic pulses. This radar system is capable of distinguishing a moving target from the non-moving objects. The non-moving objects in atmosphere that intercept the transmitted signal and scatter it are called CLUTTER. Since there will not be any DOPPLER frequency shift from fixed targets, as there is no relative motion, they are easily identified from the moving target. The echo from the moving target has the varying frequencies due to DOPPLER EFFECT.

TRACKING RADAR

A tracking radar system locks on to a particular target, measures its coordinates and provides data from which the future course of the target can be predicted.
The tracking radar is similar to other radars except that the antenna beam of a tracking radar is made to look at the target always. This is achieved by a servomechanism activated by error signals. The error signals is obtained using several techniques, viz. sequential lobing, conical scan and simultaneous lobing.

APPLICATIONS OF RADAR

Radar systems find their applications on the ground, in the air, on the sea and in space. The ground based radars have been used in the detection, location and tracking of aircraft or space targets. The shipboard radars are used to navigate the ships and to locate buoys, shorelines and other ships. They are also used to observe aircraft. The airborne radars are used to detect land vehicles, ships and aircraft. However, the principal application of airborne radar is for mapping of land storm avoidance and navigation. In space, radar is used for remote sensing purposes.

Megger(working principle)

MEGGER

Megger is the most portable insulation tester. It is used to remove very high resistances of the order of meg ohms.

PRINCIPLE:
The instrument works on the principle of ratiometer/ohmmeter. The required deflection torque is produced by both the system voltage and the current. Due to interaction between the magnetic fields produced by the voltage and the current, the deflecting torque is produced. The required coils are so positioned that the deflecting torque is proportional to the ratio, V/I.

CONSTUCTION:
It consists of
i. A small hand drives d.c. generator
ii. A moving element which has 2 coils, a deflecting coil (or current coil) and a controlling coil (or potential coil)
iii. Calibrated scale in mega ohms.
iv. Pointer and
v. Permanent Magnet.
The two coils are rigidly mounted at right angles to each other. They are connected to the small hand driven generator. The coils move in the air gap of a permanent magnet. To protect the coils under short circuit, a limiting resistor is connected in series with the coils.




OPERATION:
Resistance to be measured is connected across the test terminals i.e. connected in series with the deflecting coil and across the generator. When currents are supplied to the coils, then they have torques in opposite directions.
If the resistance to be measured is high, no current will flow through the deflecting coil. The controlling coil will, therefore, set itself perpendicular to the magnetic axis and hence, sets the pointer at infinity.
If the resistance to be measured is small, a high current flow through the deflecting coil and the resulting torque sets the pointer to zero.
For intermediate values of resistances, depending upon the torque production, the pointer is set at a point between zero and infinity.
The hand driven generator is of permanent magnet type and it is designed to generate from 500 to 2500 volts.

Fax(Fascimile)

FAX - Facsimile

This is a telecommunication service for the transmission and reception of picture information like photographs, drawing, weather maps, etc. The picture or any document to be transmitted is mounted on a cylinder and it is scanned by a photocell linked to the cylinder. The photocell produces an electrical analog signal as a voltage variation depending upon the intensity of the light and dark spots on the document. The electrical signal thus produced is converted into frequency variations and transmitted through a telephone line. At the receiving end, the frequency variations are converted back into corresponding voltage variations that is given to a plotter for reconstructing the original picture or document. Thus a photocopy of the original picture is obtained at a distance. Similar to a telephone signal, the FAX message also occupies a bandwidth of 4 kHz.

CARD READERS

Computers have undergone revolutionary changes with the advent of integrated circuit technology. Before the appearance of these modern technologies, one of the most popular input devices was the CARD READER. The data to be fed into computer are punched on these cards using punching machines. Computer punch card is a special card of size of 7.5” x 3.25” x 0.007”. It has 12 rows and 80 columns. A special device called punching machine, whose key board is similar to the key board of modern computers, was used to punch data and information on the card. Each character punched will produce a unique set of holes, row-wise in the particular column where the character is punched. The advent of modern technologies has made cards and card readers obsolete.

BROWSING ON INTERNET

For browsing on the internet, the following tools are available.
1. Who is – refers to identification of persons.
2. Finger – provides information like username, who has last logged in, how long his session had been idle, when he has viewed his last E-mail etc.
3. UU commands – information could be received about machines connected to Internet by UUCP (Unix to Unix copy).
UU Hosts – information is received about a particular site, who is responsible for it and what sort of UUCP connections it has with other sites.
UU Where – displays the path between the machine, the user is currently using and the site machine.
4. Gopher – Gopher is a software protocol designed to search, retrieve and display documents from remote sites on internet.
5. WAIS – Wide Area Information Service. It is a software protocol having the capability of searching more than one data line. The user has the provision of choosing the data for his requirement. Then he submits the query and gets the response for the query.
6. World Wide Web (WWW) – It is the most important aspect of Internet and has accelerated the growth of Internet. It is an easy to use, point and click graphical interface. It is highly interactive having graphics, text, sound and animation, etc. It is used as a market place, art gallery, library, community centre, school, publishing house, etc. There are search tools like web index and search engines to enable the information searches and discover them more effectively.

Singam newly updated stills

Surya's Stills from the movie Singam

Actor: Surya

Actress: Anushka

Director: Hari

Music: Harrish Jayaraj

Health is Wealth

HEALTH IS WEALTH

Only a healthy man can be happy. If the body is healthy, the mind will also be healthy. A healthy mind is a happy mind. Id we are cheerful, we can do our work with enthusiasm. We will then be successful in all that we do. Thus good health is the strong foundation on which success and prosperity can be built up. Proverbs like ‘Health is wealth’ and ‘A sound mind in a sound body’ show the importance of health in human life.

Many people think that wealth or money is the most important thing. They try to earn money by sacrificing everything else. They sacrifice their peace of mind and even their health for the sake of money. They overwork and ruin their health. They do not know that an unhealthy man cannot be happy. They suffer much on account of their ill health. But they attribute their sufferings to bad luck. They may sometimes feel that if they earn more money, their sufferings will vanish.

If we have health, we can work hard and earn wealth. But if we lose our health, we cannot get it back by using money. It is true that we can buy medicines and get good treatment if we have money. But a man does not become healthy merely by getting cured of his disease. It is his ill health that makes him susceptible to various diseases. A healthy man can resist the attack of diseases.

If we realize the importance of health; we must take care to preserve our health. The most important thing is proper exercise. We should give proper exercise to every part of the body. We should devote at least half an hour every day to physical exercise. We can do this either in the morning or in the evening. It should become part of our daily routine. We should take breathing exercises also. We must eat balanced diet-food that contains carbohydrates, proteins, fat, vitamins and minerals in the right proportion. We should also sleep properly. A healthy man needs six to eight hours of sleep every day. We should keep our body in the right posture. The main part of the body-from buttocks to head-should always be kept in a straight line. We can remain healthy through proper exercise, proper breathing, proper food, proper posture and proper sleep.

(This essay is suitable for 6th, 7th, 8th and 9th std students)


-Surenthiran

CONSERVE ENERGY

ENERGY CONSERVATION IS THE FOUNDATION OF ENERGY INDEPENDENCE

PLEASE SWITCH OFF

Often over-charging the phone, i.e., leaving if plugged in even after the battery is full, leads to a wastage of electricity that nobody seems to take care of. People also sometimes forget to switch off the charger after unplugging the phone.

With 584 million mobile connections in India, one can only imagine the extent of power wastage, all due to a small act of carelessness.

While most phones have a visual reminder for when the battery is full, cell phone manufacturers could perhaps incorporate audio reminders as well.

LAPTOPS AND NETBOOKS

With new and affordable models flooding the market, sale of laptops and net books has touched 200 million units already and is growing exponentially. However, not much is being done to take care of the huge power consumed by them.

Students often leave the laptop switched on, even when they take a break which means that electricity is being consumed anyway.

While switching it off each time may not be feasible, one must practice putting it in sleep mode or in hibernation when not in use. A laptop in sleep mode/hibernation consumes 35 watts per hour used by an active screen.

The same applies to desktops and PCs. An attractive alternative here is virtualization, i.e., the process of running two or more logical computer systems on one set of hardware. Instead of installing a particular application on several computers, one could install it on to one of them and it can be accessed by all other PCs at the time. Thus a lot of power which otherwise would have been wasted is saved. Websites such as www.vmware.com and www.instantfundas.com provide details.

TELEVISION

As compared to the global average of 216 televisions for every 1000 people, India ranks 148 at 59 per 1000 people. Yet, considering our huge population, it translates into a stock of 72 million television sets in India, not a small figure by any stretch of imagination.

The television is the most common source of entertainment and news in use today, but not many think of using it in an energy efficient way.

The way one checks the price and picture quantity of television sets before purchase, one must also make a habit of checking for the energy efficiency. While most electric gadgets now come with a energy star rating, it only indicates the power consumed by a television in standby mode which actually accounts for a small amount of the total power consumed by it.

Some novel television models touted to be launched in 2010 are said to save up to 40 percent of the power consumed by television sets of today and by 2012, there will be sets that save up to 65 percent.

Till then, one can look at reducing the brightness and contrast of the television set which helps reduce power consumption. Interestingly, LCD models are more efficient than their plasma counterparts. An LCD of the same size as a plasma saves power by almost 60 percent.

AIR CONDITIONER

The air conditioner is no longer considered a luxury. At home, in malls, offices and even at college, the youth now find it difficult not to have air-conditioning, without realizing the impact of these cooling devices on the environment.

Most people are unaware of the ideal temperature for cooling that will also consume electricity in the most efficient way -24 degrees Celsius. They also do not clean and change the air filters regularly, thus not realizing the additional time taken for an air conditioner to work more effectively. Electronic devices used near the thermostat heat up the machine slower than its full capacity.

The simple act of switching off an air conditioner when the intended space is sufficiently cool can help save up to 10 percent power, as can installing an air conditioner in the right way, i.e., not exposing it to direct sunlight which wastes five percent more power.

AWARENESS ACCORDS

The most important thing for students to do is to work towards self awareness. An understanding of how much our basic facilities cost will help in knowing what steps to take towards reducing wastage.
Students must try and survey the power consumption of each house in their locality and generate subsequent bills. This will help not only to build awareness of how much power we consume and how expensive it is, but also help develop a shared vision amongst groups of students. Once they are aware of the realities, they can take it upon themselves to spread the message of conservation amongst their parents, siblings, friends, relatives and people in general. This would be the first step towards a ‘switching-off’ culture.

Students can make a difference through simple steps of which building self awareness is the first step.

One tends to think about power consumption and conservation only when they run up huge electricity bills and feel the pinch of paying large sums each. Here too, it is usually the parents who pay and students don’t even bother to know the pattern of electricity consumption within their own homes; an attitude that needs complete overhaul.

There is a famous proverb, ‘As you sow, so shall you reap’. If the youth’s indifference is in the solace that it is only the villages that will have to bear the brunt of unavailability of power, they will soon come to realize the extent of their misconception. The crisis is larger than it seems now and larger than it seems now and if not controlled in the not-so-distant future, it could affect urban areas in the same way.

CONCLUSION

It is better that we, as youth, take steps to conserve power today instead of repenting tomorrow. V S Naipaul once described India as an area of darkness. It might seem funny but the truth is that by switching off our lights regularly, we may actually bring light to a large part of the country. It is not about idealism. It is about securing our own future from falling into an area of darkness in a pragmatic way.


(This article is suitable for the students of 10th, 11th, 12th std and engineering.)

-Surenthiran

Cinema and its uses

CINEMA AND ITS USES

Today no media is more popular than cinema. Every show of cinema hall is seen crowded with men and women, young and old, poor and rich. Cinema has influenced the imagination of every class of people-lower, middle and upper-alike. Children are seen murmuring film songs on the streets, young men talking about film stars and college girls are seen with film magazines in their hands. The existence of a cinema hall in the city is considered as necessary as hospital or school or park. The wide popularity of cinema is due to its manifold advantages. Besides being the most common and cheapest form of entertainment and recreation, cinema has its impact on education also. Its educational value cannot be denied. Cinema can rightly be called a good teacher as it is an effective medium of imparting education. Cinema influences the minds of children. Children’s minds are very sensitive and expression received by them will fix firmly in their minds. Children can be taught subjects like geography, history, botany, zoology, etc., through the medium of film.

Cinema and documentary films serve as a powerful agency for moulding public opinion. They also bring the people of one part of the country in contact with people living in another part and in this way serve as a means of cheap recreation and raising sex sentiments. Profit making has become the sole aim of cinema producers. What is needed is the organization of a ‘purity’ campaign for cinema films, the aim of which should be the eradication of sex, violence, etc., from the films. Production of short films on subjects should be encouraged. It would thus raise the mortal and spiritual value of films which would then be a real friend of ours.


(This article is suitable for 6th, 7th and 8th std students)

-Surenthiran

ATOMIC EXPLOSION OF INDIA

India on Mar 18, 1974 conducted its first nuclear explosion in Pokharan, Rajasthan. After a gap of 24 years India again conducted two atomic explosions on 11th and 13th May, 1998. on May 11th, through explosion, India experimented an atomic-fission device, a low-yield device and a thermo-nuclear device and emerged as the first country conducting these three experiments in one explosion. The second explosion of 13th May, ’98 was mainly intended to collect details for conducting an explosion in the computer simulation method. Both explosions were successful and India emerged as a strong member among the atomic nations.



The atomic explosions conducted by India invited pro and anti reactions from India and abroad. Some people are of opinion that a developing country like India is wasting crores of rupees in the preparations of bombs and atomic weapons. But this argument cannot be accepted. The authorities have clearly indicated that India will use its atomic power only for peaceful purposes and defence.

When our neighbours are not friendly, and when they are accumulation weapons for defence purposes India can not sit idle. We must also be prepared to guard ourselves when danger is threatening us. The explosions made recently can be taken as a warning to those neighbours who are not friendly and co-operative.

India’s aim through the atomic experiments is the formation of a comprehensive atomic system. The three devices such as the fission device, the low yield device and the thermo nuclear device were experimented together and its success is a great leap in the progress of atomic power. India is the only country successfully completing these three devices simultaneously. If the plan of India is to make atom bombs, India should not have conducted these three experiments. To make a bomb similar to that exploded in Hiroshima and Nagasaki, India doesn’t need all the technical know-how which India possesses today. The experiments conducted by India through the explosions clearly show that we are not interested in making crude bombs. We are aiming at a believable atomic weapon system as well as a powerful defence mechanism.

We have developed long range missiles of high quality like Prithvi and Agni. These are better than the bombers for the defence purposes. Now through the success in the experiments conducted by the nuclear explosions, India can equip the latest missiles more safely and successfully. In other words, the result of these atomic explosions will clearly set a strong missile system for the defence purposes. The knowledge gained from these explosions can be used in the other fields of Science and technology too.

In this modern world, where dangers through neighbours cannot be predicted, every nation should guard themselves. For this, use of atomic power and the related technologies cannot be blamed. But it should not be used for attacks or destructive purposes. There are so many peaceful uses of this power. All nations should understand the dangers of atomic power misuse and subsequent disasters. The proposed comprehensive Test Ban Treaty is to aim at this direction. But the provisions adopted in the treaty is beneficial for those countries who have stocked enough atomic weapons already. This is the main objection of India in signing the treaty. An atomic Test Ban Treaty is appreciable for a peaceful life. But that should be prepared as per the satisfaction and approval of all nations concerned.

Any way in a fast developing modern world all countries should take care to see that they are self sufficient in all matters. They should move pace to pace with other countries. The developing countries like India should work hard to attain this goal. In this hectic run, we have to take help form various forces and modern technologies. The help we plan to receive from the atomic experiments must also be considered in that way. This is an important leap to safety and prosperity.


(This essay is suitable for 7th, 8th and 9th std students)

-Surenthiran