Satellite Communication MCQ for ESE

In this section, you will get all types of Satellite Communication MCQ for ESE which were asked in previous years’ papers or which can be asked in upcoming exams.

Sr. No	Topic Wise Communication Systems MCQs for ESE
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2.	Random Variables MCQs For ESE
3.	Digital Communication MCQ for ESE
4.	Information Theory MCQs for ESE
5.	Satellite Communication MCQs for ESE

Satellite Communication MCQ for ESE

1. For identifying a radar target in a non-lossy medium, the range of the targets is to be doubled. The RF power radiated must be increased by

(a) 2 times
(b) 4 times
(c) 8 times
(d) 16 times

Answer: (d) 16 times

Explanation: $P_r = \frac{P_tG_tA_e\sigma}{(4\pi)^2 R^4}$

\therefore P_t \propto R^4

2. 13 dBm is equivalent to

(a) 2 mW
(b) 20 W
(c) 20 mW
(d) 2 MW

Answer: (c) 20 mW

Explanation: $13 = 10 \log \left(\frac{P}{10^{-3}} \right )$

\Rightarrow \frac{P}{10^{-3}}=(10)^{1.3}=20

P = 20 mW

3. The system shown in the given figure is

(a) a LOS link
(b) a satellite transponder
(c) a low noise amplifier
(d) a frequency divider

Answer: (b) a satellite transponder

4. Antenna elevation angle at the ground station for satellite communication is always kept above 5o to

(a) minimize the sky noise temperature
(b) reduce the effect of oxygen and water vapor absorption on the antenna noise temperature
(c) minimize the slant range
(d) increase the visibility of the satellite

Answer: (d) increase the visibility of the satellite

5. Random satellites move in

(a) random paths
(b) polar orbits
(c) geaostaitonary orbits
(d) equatorial plane

Answer: (b) polar orbits

6. Which one of the following statements on communication by geosynchronous satellites is correct?

The propagation loss over each direction (uplink or downlink) is about 200 dB at 5 GHz.
The radius of the geosynchronous orbit is 35860 km.
An arc of about 17^o must be covered by the satellite antenna in the equatorial plane.
The polar region is well covered by the satellite antenna.

Select the correct answer using the codes given below:

(a) 1, 2 and 4
(b) 2 and 3
(c) 1 and 4
(d) 1, 2 and 3

Answer: (c) 1 and 4

Explanation: In the 2nd option it is written that the radius of geosynchronous orbit is 35860 km which is wrong. Actually, it is the distance of orbit from Earth.

7. A TV station works at 300 MHz and radiated 100 kW of power. This signal received at a distance of 200 km will be

(a) a few μv/m due to attenuation by the Atmosphere
(b) 1-5 mv due to ionosphere reflection
(c) nil since propagation is a line of sight
(d) nil because the signal fades completely at 300 Mhz

Answer: (c) nil since propagation is a line of sight

8. In the free space line of sight propagation case, the transmission losses between the transmitter and the received increase with frequency (f) as

(a) f
(b) f²
(c) f⁴
(d) f^1/2

Answer: (b) f²

9. A TV signal transmitted in New Delhi can be received in Nagpur which is about 1000 km away if and only if

(a) Transmitting antenna is at a height of 5000 m
(b) A cable TV system is employed
(c) Power of the order of 100 kW is radiated
(d) A satellite is employed for this

Answer: (b) A cable TV system is employed

10. Which one of the following techniques is not suitable for automatic satellite tracking?

(a) Monopulse tracking
(b) Step-track
(b) Conical scanning
(d) Lobe switching

Answer: (b) Step-track

11. What should be the frequencies used for communication inside the coal mines, from the viewpoint of minimizing the propagation path loss?

(a) In the range from 30 MHz to 400 MHz
(b) In the range from 1 GHz to 4 GHz
(c) In the range from 500 MHz to 1 GHz
(d) In the range from 1 GHz to 2 GHz

Answer: (a) In the range from 30 MHz to 400 MHz

Explanation: Since the path loss ∝ f², so frequencies used for communication inside the coal mines should be low to minimize the path loss.

12. Which one of the following statements is not correct?

(a) A geosynchronous satellite remains practically stationary relative to Earth antennas
(b) A geosynchronous satellite means the same thing as a geostationary satellite
(c) There is a trade-off between the cost of a communication satellite and the cost of its earth stations
(d) Three geosynchronous satellites cannot give 100% global coverage

Answer: (d) Three geosynchronous satellites cannot give 100% global coverage

Explanation: Three geosynchronous satellites give 100% global coverage

13. If a satellite is launched at an orbital radius of twice that of a geostationary satellite, how much time will the launched satellite take to travel around the Earth?

(a) 48 hrs
(b) 12 hrs
(c) 96 hrs
(d) 6 hrs

Answer: (c) 96 hrs

14. A geostationary satellite located at about 35000 km from Earth can cover

(a) Complete surface of the earth
(b) One hemisphere in one pass
(c) One side of the earth
(d) An area depending on the antenna used

Answer: (c) One side of the earth

Explanation: A geostationary satellite can cover a one-third surface area of the Earth. Therefore three geostationary satellites are needed to cover the whole surface of Earth.

15. What is the reason for using frequencies of the order of a few GHz in satellite communication?

(a) Antenna sizes are small and the ionosphere does not reflect frequencies
(b) Helical antennas can be used at these frequencies
(c) Frequencies can pass through the ionosphere without attenuation
(d) Easy availability of components at these frequencies.

Answer: (a) Antenna sizes are small and the ionosphere does not reflect frequencies

16. Communication satellites are allotted a bandwidth of 500 MHz. This can be increased by using

(a) frequency and polarization re-use
(b) time-division multiplexing
(c) frequency division multiplexing
(d) triple modular redundancy

Answer: (a) frequency and polarization re-use

17. Which one of the following is correct?

(a) the uplink carrier frequencies are greater than the downlink carrier frequencies
(b) the uplink carrier frequencies are lesser than the downlink carrier frequencies
(c) both uplink and downlink carrier frequencies are the same
(d) it is not necessary to use a carrier at all

Answer: (a) the uplink carrier frequencies are greater than the downlink carrier frequencies

Explanation: Since the size of the receiver antenna in a satellite is very small in comparison to that in an earth station, therefore, to achieve a higher gain uplink carrier frequency is greater than the downlink carrier frequency.

18. What was the first commercial geostationary communication satellite?

(a) INTELSAT 1
(b) ECHO
(c) INSAT-1A
(d) SPUTNIK

Answer: (a) INTELSAT 1

19. What does a link budget for satellite communication include?

(a) Total cost of satellite
(b) Cost of satellite plus launch vehicle
(c) Signal and noise levels in dB
(d) Margins of error permitted

Answer: (c) Signal and noise levels in dB

Explanation: A link budget involves a relatively simple addition and subtraction of gains and losses in dB within an RF link.

20. In a typical satellite communication system, which one of the following could be the uplink and downlink frequencies respectively?

(a) 40 GHz and 60 GHz
(b) 60 GHz and 40 GHz
(c) 6 GHz and 4 GHz
(d) 4 GHz and 6 GHz

Answer: (c) 6 GHz and 4 GHz

21. The output stage of a transponder onboard a satellite has a maximum power output of 10 watts. However, it is not operated at the maximum power output in order to

(a) Conserve the available limited battery power
(b) Reduce noise due to the device
(c) Avoid intermodulation distortion
(d) Avoid heating the gup of the satellite beyond a per det value

Answer: (a) Conserve the available limited battery power

22. For communication from a satellite to the Earth station, microwave frequencies are used because

(a) loss is minimum
(b) nose added to signal is low in this window
(c) these do not get reflected back by the ionosphere
(d) many channels can be used

Answer: (d) many channels can be used

Explanation: By using microwaves wide bandwidth is achieved and hence many channels can be used.

23. A Geostationary orbit is chosen for communication satellites because

(a) it is stationary at one point in space
(b) with respect to a spot on Earth, it looks stationary
(c) this orbit provides Earth’s coverage of more than 50% using a single satellite.
(d) the length of 4700 km is convenient for launching

Answer: (b) with respect to a spot on Earth, it looks stationary

24. A low earth orbit satellite can provide large signal strength at an earth station because

(a) Path loss’s law
(b) These orbits are immune to noise
(c) Large solar power can be generated at these orbits
(d) Lower microwave frequencies in S-band can be used

Answer: (a) Path loss’s law

Explanation: $Path \; loss = \left( \frac{4\pi R}{\lambda} \right )^2$

If R is less then path loss will be low.

25. If ‘r’ is the radius of a circular orbit then the orbital period of a satellite is directly proportional to

(a) r^3/2
(b) r^1/3
(c) r^1/2
(d) r^2/3

Answer: (a) r^3/2

Explanation: $T^2 = \frac{4 \pi^2 r^3}{GM} \; or\; T \propto r^{3/2}$

26. In satellite communication, the uplink power level is generally high, and power level received downlink signal is low because:

High signal attenuation due to free space loss
Limited available downlink power
Finite satellite downlink antenna gain, which is dictated by the required coverage area.

(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

27. In microwave relay communication the repeater is usually an amplifier for the amplification of

(a) Carrier signal
(b) Baseband signal
(c) AMplitude modulated IF signal
(d) Frequency modulated IF signal

Answer: (b) Baseband signal

28. In a geostationary satellite communication system, a message signal is transmitted from an earth station via an uplink to a satellite amplified in a transponder on board the satellite and then transmitted via a downlink to another earth station. The most popular frequency band for satellite communication is

(a) 16 MHz for the uplink and 14 MHz for the downlink
(b) 4 GHz for the uplink and 6 GHz for the downlink
(c) 6 GHz for the uplink and 4 GHz for the downlink
(d) 10 GHz for the downlink and 8 GHz for the uplink

Answer: (c) 6 GHz for the uplink and 4 GHz for the downlink

29. As per WARC-1979 allocation, commercial communication satellites use the bandwidth of

(a) 4 MHz
(b) 40 MHz
(c) 200 MHz
(d) 500 MHz

Answer: (d) 500 MHz

30. In satellite communication, Faraday rotation is caused by

(a) Plasma Frequency
(b) Earth’s magnetic field
(c) Non-gaussian nature of uplink noise when received in the downlink channel
(d) Ionospheric reflections that occur multiple times

Answer: (b) Earth’s magnetic field

31. A satellite link uses different frequencies for receiving and transmitting in order to

(a) avoid interference from terrestrial microwave link
(b) minimize free space losses
(c) maximize antenna gain
(d) avoid interference between its powerful transmitted signal and weak incoming signal

Answer: (b) minimize free space losses

Explanation: To minimize the path loss the uplink frequency should be more than the downlink frequency

32. The frequency range of very high frequency (VHF) is

(a) 300 MHz – 3000 MHz
(b) 30 MHz – 300 MHz
(c) 3 MHz – 30 MHz
(d) 30 THz – 3000 Hz

Answer: (b) 30 MHz – 300 MHz

33. Maximum frequency reflected from the ionosphere is 9 MHz on a particular day. The maximum ion density/meter³ is

(a) 10⁸
(b) 10⁶
(c) 10¹²
(d) 10⁹

Answer: (c) 10¹²

Explanation: $f = 9 \sqrt{N_{max}}$

9 \times 10^6 = 9 \times \sqrt{N_{max}}

34. The frequency range for satellite communication is

(a) 1 KHz – 100 KHz
(b) 100 KHz – 1 MHz
(c) 10 MHz – 30 MHz
(d) 1 GHz – 30 GHz

Answer: (d) 1 GHz – 30 GHz

Explanation: The frequency range of satellite communication is in GHz.

35. The linear velocity of a satellite, when in a circular orbit is

(a) directly proportional to its mass
(b) directly proportional to the square root of its mass
(c) directly proportional to the square of its mass
(d) independent of its mass

Answer: (d) independent of its mass

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Satellite Communication MCQ for ESE

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