# Analog Communications Questions and Answers – Time Division Multiplexing

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This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Time Division Multiplexing”.

1. The real part of an antenna’s input impedance is due to ________
a) SWR
c) reflected signal
d) refracted signal

Explanation: In antenna impedance, impedance related the voltage and current at the input of the antenna. The real part of antenna impedance represents power that is either radiated away or absorbed within the antenna and the imaginary part of antenna impedance represents power that is stored in the near field of antenna.

2. What is the other name for half-wave dipole antenna?
a) Helical antenna
b) Isotropic antenna
c) Hertz antenna
d) Maxwell antenna

Explanation: The Hertz antenna is also known as half wave dipole antenna. It consists of two straight collinear conductors of equal length separated by a small feeding gap.

3. Measured on the ground, the field strength of a horizontally polarized half wave dipole antenna is strongest ________
a) in one direction
b) in two directions
c) depends on the number of elements
d) depends on the shape of antenna

Explanation: As the name suggests, half wave dipole is half wavelength long. This antenna has the shortest resonant length that can be used for a resonant dipole. The field strength of a horizontally polarized half wave dipole antenna is strongest in two directions.
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4. When an antenna radiates more energy in one direction than in other directions, it is called ________
a) selectivity
b) directivity
c) active antenna
d) resonance

Explanation: When an antenna radiates more energy in one direction than in other directions is called directivity. An antenna that radiates equally in all directions has effectively zero directionality, and the directivity of this type of antenna should be 1 (or 0dB).

5. What is the full form of ERP?
a) Effective Radiated Power
b) Effective Reflected Power
c) Equivalent Radiated Power
d) Equivalent Reflected Power

Explanation: ERP stands for Effective Radiated Power. Effective Radiated Power (ERP) is always given with respect to a certain direction.
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6. “Ground Effect” in antenna caused by ________
a) faulty connection of the feed cable ground
c) buildings and other structures on ground
d) radio signals reflecting off the ground

Explanation: Radio signals that are reflecting back from the ground is responsible for ground effects in antenna.

7. The polarization of plane waves received from satellite is changed by ________
b) Gamma rays
c) Helical rotation
d) Distance travelled

Explanation: Generally for satellite communication circular polarization is required. The polarization received by waves from satellite is changed by Faraday rotation.

8. What is the input impedance to a lossless antenna, at resonance?
a) infinite
b) 0
c) resistive
d) capacitive

Explanation: In antenna impedance, impedance related the voltage and current at the input of the antenna. The real part of antenna impedance represents power that is either radiated away or absorbed within the antenna and the imaginary part of antenna impedance represents power that is stored in the near field of antenna. The input impedance of a lossless antenna is purely resistive.

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