This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Asynchronous TDM”.
1. Which is the standard reference antenna for the directive gain?
a) Isotropic antenna
b) Marconi antenna
c) Helical antenna
d) Log Periodic antenna
Explanation: Isotropic antenna is an ideal antenna that radiates its power uniformly in all directions. In practical, no isotropic antenna exists. It is often used as a reference antenna for the antenna gain. Directive gain of a practical antenna is the ratio of the radiation intensity of the antenna to that of an isotropic antenna.
2. Which one of the following reasons for the use of a ground screen with antennas is false?
a) Impossibility of a good ground connection
b) Provision of an earth for the antenna
c) Protection of personnel working underneath
d) Improvement of radiation pattern of antenna
Explanation: If we consider the use of ground as a screen with antenna then there is no chance that it is used for protection of personnel working underneath.
3. Which of the following antennas is best excited from a waveguide?
Explanation: A horn is an antenna that consists of a flaring metal waveguide that is shaped like a horn. The horn shape helps to direct radio waves in a beam. It is widely used as antennas at UHF.
4. An ungrounded antenna near the ground ________
a) must be horizontally polarized
b) acts as an antenna array
c) is unlikely to need a ground screen
d) acts as a single antenna of twice the height
Explanation: An ungrounded antenna near the ground acts as an antenna array. An antenna array is a combination of multiple antennae which function as a single antenna to perform the required task.
5. Field strength at a distance from an antenna is measured with __________
a) a slotted line
b) a dipole
c) an EIRP meter
d) a field strength meter
Explanation: Field strength meter is an instrument which is used to measure the electric field strength emanating from a transmitter. EIRP (Effective Isotropic Radiated Power) meter is used to measure the radiated power of an antenna in a specific direction.
6. The radiated beam from a parabolic “dish” transmitting antenna is ________
Explanation: The radiated beam from a parabolic “dish” transmitting antenna is collimated. Collimated light is that light whose rays are parallel due to which it disperse minimally as it propagates.
7. What is the full form of LPDA?
a) Log Periodic Dipole Array
b) Log Periodic Dispersed Array
c) Low Periodic Dispersed Array
d) Low Power Dipole Array
Explanation: LPDA stands for Log Periodic Dipole Array. LPDA consists of a number of half-wave dipole driven elements which gradually increases in length.
8. Arrays in antenna can be __________
d) phased, driven or parasitic
Explanation: An antenna array is a group of multiple antenna which behaves as a single antenna to perform the required tasks. Arrays in the antenna can be phased, driven or parasitic.
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