WorksheetsDigital Communications
Total questions: 20
Worksheet time: 31mins
Modulation is done in
radio receiver
transmitter
between transmitter and receiver
None of the above
In an AM wave the majority of the power is in
lower sideband
Carrier
Upper Sideband
None of the above
Modulation refers to a low frequency signal controlling the
amplitude of the carrier
frequency of the carrier
phase of the carrier
any of the above
Noises are variations in
amplitude
frequency
phase
both phase and frequency
If level of modulation is increased ................ power is increased.
carrier
carrier as well as sideband
sideband
None of the above
At 100% modulation the power in each sideband is ............ of that of carrier.
50%
40%
60%
25%
Overmodulation results in
weakening of the signal
excessive carrier power
distortion
none of the above
The major advantage of FM over AM is
reception is less noisy
higher carrier frequency
smaller bandwidth
small frequency deviation
Which are the additional stages in FM receiver
AF amplifier
limiter
descriminator
selector
None of the above
The antenna length is smaller for FM broadcasting because the wavelength of FM is short
True
False
For FM the value of modulation index can be greater than 1
True
False
AM wave contains three frequencies
True
False
The process of recovering the audio signal from the modulated wave is known as (a)
In FM the amplitude of the wave is
remains same as carrier
reduces
increases
none of the above
The bandwidth of AM wave is ....... times signal frequency
0
2
1
4
None of the above
The maximum peak to peak voltage of an AM wave is 16 mV while the minimum peak to peak voltage is 8 mV. Find the percent modulation
33.33%
55%
60%
66%
An AM transmitter supplies 10 kW to the antenna when unmodulated. Determine the total power radiated by the transmitter when modulated to 30%
11%
10.45%
9.5%
12.45%
The r.m.s antenna current of an AM transmitter increases by 15 % over the unmodulated value when sinusoidal modulation is applied. What is the modulation index
0.7
0.5
0.8
1
The r.m.s value of carrier voltage is 100 V. After amplitude modulation by an audio signal, r.m.s value becomes 110.Calculate the modulation index
64.8%
68.4%
66.45%
60%
A certain AM transmitter radiates 8kW with carrier unmodulated and 9kW when the carrier is modulated. Find the percentage modulation
25%
60%
50%
0.5%
