10
MCQ (Multiple Correct Answer)
An audio signal of 15 kHz frequency cannot be transmitted over long distances without modulation, because
A
the size of the required antenna would be at least 5 km which is not convenient
B
the audio signal can not be transmitted through sky waves
C
the size of the required antenna would be at least 20 km , which is not convenient
D
effective power transmitted would be very low, if the size of the antenna is less than 5 km
11
MCQ (Multiple Correct Answer)
Audio sine waves of 3 kHz frequency are used to amplitude modulate a carrier signal of 1.5 MHz . Which of the following statements are true?
A
The side band frequencies are 1506 kHz and 1494 kHz
B
The bandwidth required for amplitude modulation is 6 kHz
C
The bandwidth required for amplitude modulation is 3 MHz
D
The side band frequencies are 1503 kHz and 1497 kHz
12
MCQ (Multiple Correct Answer)
A TV transmission tower has a height of 240 m . Signals broadcast from this tower will be received by LOS communication at a distance of (assume the radius of earth to be $\left(6.4 \times 10^6 \mathrm{~m}\right)$
A
100 km
B
24 km
C
55 km
D
50 km
13
MCQ (Multiple Correct Answer)
The frequency response curve (figure) for the filter circuit used for production of AM wave should be
A
(i) followed by (ii)
B
(ii) followed by (i)
C
(iii)
D
(iv)
14
MCQ (Multiple Correct Answer)
In amplitude modulation, the modulation index $m$, is kept less than or equal to 1 because
A
$m>1$, will result in interference between carrier frequency and message frequency, resulting into distortion
B
$m>1$, will result in overlapping of both side bands resulting into loss of information
C
$m>1$, will result in change in phase between carrier signal and message signal
D
$m>1$, indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion