Which of the following is the disadvantage of FM over AM?
Larger band width requirement
Larger noise
Higher modulation power
Low efficiency
If a number of sine waves with modulation indices n1, n2, n3........ Modulate a carrier wave, and then total modulation index (n) of the wave is ____.
n1 + n2.... + 2(n1 + n2.....)
None of the above
An AM wave has 1800 watt of total power content, For 100% modulation the carrier should have power content equal to ____.
1000 watt
1200 watt
1500 watt
1600 watt
The frequency of a FM transmitter without signal input is called____.
lower side band frequency
upper side band frequency
resting frequency
None of the above
What type of modulation is employed in India for radio transmission ?
Amplitude modulation
Frequency modulation
Pulse modulation
None of the above
When the modulating frequency is doubled, the modulation index is halved and the modulating voltage remains constant, the modulation system is ____.
amplitude modulation
phase modulation
frequency modulation
All of the above
An antenna is a device ____.
that converts electromagnetic energy into radio frequency signal
that converts radio frequency signal into electromagnetic energy
that converts guided electromagnetic waves into free space electromagnetic waves and vice-versa
None of the above
While tuning in a certain broadcast station with a receiver, we are actually ____.
varying the local oscillator frequency
varying the frequency of the radio signal to be picked up
tuning the antenna
None of the above
Indicate which one of the following system is digital?
Pulse position modulation
Pulse code modulation
Pulse width modulation
Pulse amplitude modulation
In a communication system, noise is most likely to affect the signal ____.
at the transmitter
in the channel or in the transmission line
in the information source
at the receiver
The waves used in telecommunication are ____.
IR
UV
Microwave
Cosmic rays
In an FM system a 7 kHz signal modulates 108 MHz carrier so that frequency deviation is 50 kHz. The carrier swing is ____.
7.143
8
0.71
350
Consider telecommunication through optical fibers. Which of the following statements is not true?
Optical fibers may have homogeneous core with a suitable cladding
Optical fibers can be of graded refractive index
Optical fibers are subject to electromagnetic interference from outside
Optical fibers have extremely low transmission loss
The phenomenon by which light travels in an optical fibers is____.
reflection
refraction
total internal reflection
transmission
Television signals on earth cannot be received at distances greater than 100 km from the transmission station. The reason behind this is that ____.
the receiver antenna is unable to detect the signal at a distance greater than 100 km
the TV program consists of both audio and video signals
the TV signals are less powerful than radio signals
the surface of earth is curved like a sphere
Advantage of optical fiber ____.
high bandwidth and em interference
low bandwidth and em interference
high band width, low transmission capacity and no em interference
high bandwidth, high data transmission capacity and no em interference
In frequency modulation ____.
the amplitude of modulated wave varies as frequency of carrier wave
the frequency of modulated wave varies as amplitude of modulating wave
the amplitude of modulated wave varies as amplitude of carrier wave
the frequency of modulated wave varies as frequency of modulating wave
Audio signal cannot be transmitted because ____.
the signal has more noise
the signal cannot be amplified for distance communication
the transmitting antenna length is very small to design
the transmitting antenna length is very large and impracticable
In which of the following remote sensing technique is not used?
forest density
pollution
wetland mapping
medical treatment
For sky wave propagation of a 10 MHz signal, what should be the minimum electron density in ionosphere?
~ 1.2 ( 1012 m–3
~ 106 m–3
~ 1014 m–3
~ 1022 m–3
What should be the maximum acceptance angle at the air core interface of an optical fiber if n1 and n2 are the refractive indices of the core and the cladding, respectively ____.