This set of Basic Analog Communications Questions and Answers focuses on “Practical Aspects of Sampling”.
1. An antenna can be matched to a feed line by using an LC network only.
Explanation: An antenna can be matched to a feed line, also known as a transmission line, by using an LC network. But it can also be matched to feed line by a loading coil.
2. An array with one driven element, a reflector, and one or more directors is called ________
c) Simple Dipole
d) Folded Dipole
Explanation: A Yagi-Uda antenna is a directional antenna consisting of many parallel elements in a line. It consists of a single driven element which is connected to the transmitter or receiver with a transmission line and also contains parasitic elements which are not connected to the transmitter or receiver. Thus, there are three or four directors and one reflector.
3. The energy picked up by a parabolic antenna is concentrated at the ________
Explanation: A parabolic antenna is one with parabolic reflector. Energy picked up by a parabolic antenna is concentrated at the focus.
4. Antennas are often tested in ________
a) an RF reflective chamber
b) a vacuum chamber
c) an anechoic chamber
Explanation: 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. They are often tested in an anechoic chamber. An antenna is used to transmit high frequency waves and plays significant role in the communication process.
5. Which one of the following consists of non-resonant antennas?
a) folded dipole
b) simple dipole
c) rhombic antenna
d) broadside array
Explanation: Non-resonant antennas are like non-resonant transmission lines. Non-resonant transmission lines do not have standing waves. Hence they do not have any reflected wave and they have only forward travelling wave. Whereas resonant antennae have standing wave patterns.
6. Which one of the following is very useful as a multiband HF receiving antenna?
a) folded dipole
b) log periodic
c) conical horn
d) rectangular horn
Explanation: A log periodic antenna is a multi-element, directional, antenna designed to operate over a wide band of frequencies. Whereas, folded dipole and rest work over short band frequencies.
7. Which among the following is not a reason for the use of antenna coupler?
a) To make the antenna look resistive
b) To provide the output amplifier with correct load impedance
c) To discriminate against harmonics
d) To prevent re-radiation of the local oscillator
Explanation: Antenna coupler is a device connected between a radio transmitter or receiver and its antenna to improve power transfer between them. Antenna coupler is never used to prevent re-radiation of the local oscillator.
8. Which of the following term is not applied to the Yagi-Uda array?
a) low impedance
b) high gain
c) good bandwidth
d) high reception of signals
Explanation: A Yagi-Uda antenna is a directional antenna consisting of many parallel elements in a line. It consists of a single driven element and also contains parasitic elements. It consists of 3 or 4 directors and 1 reflector.
9. Why top loading is used with an antenna?
a) to increase its effective height
b) to increase its beamwidth
c) to increase its bandwidth
d) to increase its impedance
Explanation: Length of an and it’s height are significant parameters for the functioning of the antenna. When length of the antenna is shorter than a quarter wavelength (ʎ⁄4), top loading is used to increase its effective height.
Sanfoundry Global Education & Learning Series – Analog Communications.
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