This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Linear Modulation”.
1. Discone antenna is mainly used in UHF range.
Explanation: Discone antenna is omnidirectional so it is mainly used in UHF range. It is especially used in airports. Discone antenna is a combination of disc and cone.
2. Squelch circuit is normally inserted in receiver ________
a) after detector
b) before detector
c) before mixer
d) after power amplifier
Explanation: Squelch is added to suppress noise. It is added after detector when there is no carrier.
3. Each frequency gives rise to four side bands.
Explanation: Each frequency in communication gives rise to two side bands.
4. Field strength (E) is directly proportional to the square of transmission power.
Explanation: Actually the Field strength (E) is directly proportional to the square root of transmission power i.e. E ∝ √Pt
5. If the transmitted power is 100KW then the field at a distance ‘R’ is 60mV/m. Suppose if the transmitted power is reduced to 50KW then the field at same distance ‘R’ will be equal to ________
6. If the value of resistor becomes 16 times than its previous value then its noise voltage will become ________
a) 16 times
b) 8 times
c) 4 times
d) 2 times
Explanation: Since the noise voltage is directly proportional to square root of resistance so if the value of resistor increased to 16 times then its noise voltage will become 4 times.
7. What is the modulation index for a single tone modulation, given that positive peak of AM wave is 20V and minimum value is 2V?
Explanation: Average value = 11V. So, modulation index = (20-11)/11 = 0.81
8. TV remote control used ultra violet light.
Explanation: Each time we press any button of TV remote it sends a beam of infrared rays. For different commands it sends out different beam which is detected by a microchip lying inside TV.
9. How capacitance is related with thickness?
a) it is inversely proportional to thickness
b) it is directly proportional to thickness
c) it is inversely proportional to twice of thickness
d) it is directly proportional to twice of thickness
Explanation: Capacitance, C = A×∈⁄t so it is inversely proportional to thickness.
10. Noise gets mixed with signal at ________
Explanation: It acts as a path for taking signals to the receiver. There is a high probability of involving noise at the channel.
Sanfoundry Global Education & Learning Series – Analog Communications.
To practice all areas of Analog Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.