To study electromagnetic radiations from astronomical objects, radio astronomers

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Question
To study electromagnetic radiations from astronomical objects, radio astronomers use
Options
A. low frequencies
B. medium frequencies
C. microwaves
D. either (a) or (b)

Correct Answer

microwaves

Microwave Communication problems

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1. Consider the following statements
1. Usable bandwidth of ridge wave guide is more than that of rectangular waveguide.
2. For a given value of TM₁₀ cutoff frequency the cross section of ridge wave guide is lesser that that of rect angular waveguide.
3. Ridge wave guide has higher conductor losser than a rectangular waveguide.
4. Ridge guide has higher conductor losser than a rectangular waveguide.
Which of the above statements are correct?
Options
A. 1 and 2 only
B. 1, 2 and 3 only
C. 2 and 3 only
D. All

3. Interference generated by electrical equipment and automobile ignition systems when observed closed to earth is
Options
A. horizontally polarized
B. vertically polarized
C. polarized both horizontally
D. not polarized

5. A rectangular waveguide has two stubs each length connected at the source end. The stubs are short circuted. Then
Options
A. the longitudinal current is power current and current in stubs is reactive
B. the longitudinal current is reactive current and current in stubs is power current
C. both power and reactive exists in both longitudinal direction and stubs
D. the current in stubs is zero

6. In laboratory experiment the output from reflex klystron is moderated by square wave because
Options
A. it is easy to generate a square wave
B. crystal diode operates in square law region of i-v characteristics
C. it prevents frequency modulation
D. detector circuit is less complicated

7. In a TWT the loss in attenuator is
Options
A. almost equal to forward gain of tube
B. much less than forward gain of tube
C. much higher than forward gain of tube
D. almost infinite

8. For a waveguide, which of the following statements is wrong?
Options
A. It is usually made of brass or aluminium
B. It is usually rectangular or circular in shape
C. The dielectric region is usually air
D. The wall thickness is very small as compared to skin depth

9. A magic tee is to be used as CW duplexer. Then port 1, port 2, port 3 (E arm), port 4 (H arm) respectively should be connected to
Options
A. matched load, antenna, receiver and CW transmitter
B. CW transmitter, antenna, receiver and matched load
C. CW transmitter, receiver, antenna and matched load
D. CW transmitter, matched load, receiver and antenna

10. Two identical hybrid tees are joined as shown in the given figure. If 16 mW power is fed into port 1, the power output at ports 2 , 3, 1', 2', 3' respectively is
Options
A. 8, 4, 2, 2, 0 mW
B. 0, 8, 4, 4, 0 mW
C. 0, 8, 2, 2, mW
D. 8, 2, 4, 2, 0 mW

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