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Analog Communications Multiple Choice Questions focuses on “Synchronous TDM”.
1. As the length of a long-wire antenna is increased ________
a) the number of lobes also increase
b) the number of lobes decrease
c) efficiency increase
d) the number of nodes decreases
Answer: a
Clarification: An antenna is basically a transducer that converts radio frequency fields into alternating current or vice versa. They can be used for both transmission and reception of radio signals. If the length of a long wire antenna is increased then the number of lobes also increases. The reception capability of an antenna also depends on it’s length.
2. A non-resonant antenna will ________
a) not transmit
b) not receive
c) cause SWR on the feed cable
d) transmit and receive the signal at the same time
Answer: c
Clarification: A non-resonant antenna have wider bandwidth as compared to the resonant antenna. It also has less sensitivity than resonant antenna. Having less sensitivity means it can amplify weak signals efficiently. A non-resonant antenna will cause SWR on the feed cable.
3. The typical antenna in an AM radio is a ________
a) dipole
b) helical
c) ferrite “loop-stick”
d) loop dipole
Answer: c
Clarification: A ferrite rod antenna is a form of RF design that is universally used in portable transistors broadcast receivers. It is also being used increasingly in wireless applications in areas such as RFID. It is a type of typical antenna in an AM radio. Dipole antenna is the simplest form of antenna. Helical antenna is antenna having quarter wavelength.
4. A 1-MHz monopole antenna must be ________
a) mounted vertically
b) mounted horizontally
c) atleast half lambda wavelength long
d) atleast lambda wavelength long
Answer: a
Clarification: A monopole antenna consists of a straight rod shaped conductor. It is often mounted perpendicularly over some type of conductive surface, called a ground plane.
5. “Ground Effects” in antenna effects ________
a) antenna’s radiation
b) antenna’s gain
c) antenna’s SWR
d) antenna’s power
Answer: a
Clarification: Ground generally reflects the wave back that comes to it. It also affects antenna by effecting the radiation. The radiation intensity of an antenna is determined by comparing it with that of isotropic antenna.
6. An antenna’s beamwidth is measured ________
a) from +90° to -90°
b) between half power points
c) between the minor side lobes
d) between the major side lobes
Answer: b
Clarification: The angle between the half power points of the main lobe with respect to the peak effective radiated power is called half power beamwidth. It is generally measured between half power points.
7. What is the front to back ratio of a half wave dipole antenna?
a) 0 dB
b) 10 dB
c) 100 dB
d) 50 dB
Answer: a
Clarification: The front to back ratio means the ratio of power gain between the front and back of a directional antenna. A half-wave dipolr antenna is one with length half of the wavelength. For a half-wave dipole antenna, its value comes out to be 0dB.
8. AM waves is represented by Et cos ωc t. What does Et denotes?
a) amplitude of modulated wave
b) amplitude of carrier signal
c) amplitude of modulating signal
d) amplitude of message signal
Answer: a
Clarification: AM wave is represented by Ac(1+xt) cos ωc t or Et cos ωc t, where xt is modulating signal, Ac is amplitude of carrier wave and Et is amplitude of AM wave.
9. The radiation of energy from an antenna can be seen in the ________
a) standing wave around antenna
b) radiation resistance of the antenna
c) reflected resistance of the antenna
d) I2R loss of the antenna
Answer: b
Clarification: An antenna is basically a transducer that converts radio frequency fields into alternating current or vice versa. They can be used for both transmission and reception of radio signals. Radiation resistance of the antenna is just a measure of radiation of energy from antenna.
10. The end-to-end length of a half wave dipole antenna is actually ________
a) slightly shorter than a half wavelength
b) slightly longer than a half wavelength
c) half lambda wavelength
d) lambda wavelength
Answer: a
Clarification: The half wave dipole antenna is also known as Hertz antenna. It consists of two straight collinear conductors of equal length separated by a small feeding gap. The length of half wave dipole antenna is slightly shorter than half wavelength. It’s the simplest form of an antenna.
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