MCQ in Modulation Part 3 | ECE Board Exam

This is the Multiples Choice Questions Part 3 of the Series in Modulation as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Amplitude Modulation
• MCQ in Phase Modulation
• MCQ in Sound Pressure Level
• MCQ in Frequency Modulation
• MCQ in Pulse Modulation

Continue Practice Exam Test Questions Part 3 of the Series

101. It is the width of frequencies within the spectrum occupied by a signal and used by the signal for conveying information.

A. Band

B. Bandwidth

C. Electronic spectrum

D. Frequency band

102. Which transmit only one sideband?

A. H3E

B. C3F

C. A3E

D. B8E

103. ______ is kind of modulation in which the modulated wave is always present.

A. Carrier modulation

B. Continuous modulation

C. Log-periodic modulation

D. Square-wave modulation

104. A type of modulation in which no signal is present between pulses.

A. Pulse modulation

B. FSK

C. QAM

D. PAM

105. What describes the amount of amplitude change present in an AM waveform?

A. Percent modulation

B. Modulation constant

C. Envelope of modulation

D. Coefficient of modulation

106. _______ is a form of amplitude distortion introduced when the positive and negative alternations in the AM modulated signals are not equal.

A. Envelope distortion

B. Spurious emission

C. Carrier shift

D. Johnson noise

107. What is the advantage of phase modulation over direct FM frequency modulation?

A. Multipliers can be used

B. The deviation is smaller

C. Simplicity and practicality

D. The oscillator is crystal-controlled

108. If the spectrum is shifted in frequency with no other changes, this is known as

A. Frequency multiplication

B. Sideband movement

C. Baseband reorientation

D. Frequency translation

109. A device which is capable of causing frequency translation

A. High-Q tank circuit

B. Balanced modulator

C. Low-Q tank circuit

D. IF strip

110. If the frequency of each component in a signal spectrum is increased by the same fixed amount, this known as

A. Modulation

B. Frequency translation

C. Up conversion

D. Both B and C

111. A particular amplifier is designed to be a frequency doubler. If the input signal frequency is 15.4 MHz, a circuit in the output will be tuned to

A. 7.7 MHz

B. 15.4 MHz

C. 30.8 MHz

D. 61.6 MHz

112. A sine wave of 293 MHz is phase-modulated to achieve a maximum phase deviation of 0.2 radian. After passing through a frequency tripler, the maximum phase deviation will be

A. 0.2 radian

B. 0.3 radian

C. 0.4 radian

D. 0.6 radian

113. Any device to be used as a frequency multiplier must be

A. Active

B. Passive

C. Linear

D. Nonlinear

114. A particular amplifier circuit used for frequency doubling.

A. Push-push

B. Push-pull

C. Pull-push

D. Pull-pull

115. Frequency division is useful in the implementation of a

A. AM demodulator

B. Frequency synthesizer

C. AGC circuit

D. FM demodulator

116. Frequency division by 12 will require how many flip-flops in the counter?

A. 3

B. 4

C. 6

D. 12

117. Identify an electronic device, not specifically designed for the purpose, which can be used as a phase detector.

A. Wien bridge

B. Colpitts oscillator

C. Balanced modulator

D. Butterworth filter

118. A particular frequency synthesizer contains only a single crystal. What words describe this synthesizer?

A. Crystal modulated

B. Inexact

C. Indirect

D. Deficient

119. A recognizable feature of a CW transmitter is

A. Keyed transmitter

B. Power amplification

C. Frequency generation

D. All of these

120. The term “pulling” refers to

A. The change of the crystal oscillator frequency by loading

B. One half-cycle operation of a push-pull amplifier

C. Loading on the transmitter caused by the antenna connection

D. Reduction of the power supply terminal voltage as the transmitter is keyed.

121. When frequency modulation is achieved by initial phase modulation, this is called

A. Angular modulation

B. Direct FM

C. Indirect FM

D. Indirect synthesis

122. A disadvantage of direct FM is the need for

A. AGC

B. AFC

C. A frequency synthesizer

D. Phase modulation

123. Direct FM can be achieved by

A. A reactance tube modulator

B. A varactor diode

C. And AGC circuit

D. Both A and B

124. A receiver in which all RF amplifier stages require manual tuning to the desired RF is called

A. Superheterodyne

B. Autodyne

C. TRF

D. AFC

125. Why is it often necessary to precede the demodulator by amplifier stages in a receiver?

A. To improve fidelity

B. To reduce receiver noise

C. To eliminate image response

D. Weak antenna signals

126. A serious disadvantage of the TRF receiver.

A. Bandwidth variations over the tuning range

B. The weight and cost

C. The requirements for a closely regulated power supply

D. The requirements for a half-wave antenna

127. Identify which is not a part of a superheterodyne receiver.

A. Local oscillator

B. Modulator

C. IF amplifier

D. Demodulator

128. Which major element will not be found in every superheterodyne receiver?

A. R–F amplifier

B. Mixer

C. Local oscillator

D. IF amplifier

129. Which major element of a superheterodyne receiver must be nonlinear?

A. R-F amplifier

B. Mixer

C. Local oscillator

D. IF amplifier

130. The change of the modulated carrier frequency from the original RF to the IF of the superheterodyne receiver is known as

A. Frequency multiplication

B. Frequency allocation

C. Frequency substitution

D. Frequency translation

131. The key to achieving receiver sensitivity is the reduction of

A. Image response

B. Mixer harmonic products

C. Spurious frequency response

D. Internal noise

132. Which of the following receiver design objectives is not impossible?

A. Elimination of galactic noise

B. Elimination of atmospheric noise

C. Elimination of man-made noise

D. Reduction of receiver internal noise

133. In comparing the S/N ratio for the input to the receiver with the S/N ratio for the output, the latter is

A. Smaller

B. The same

C. Greater

D. Infinite

134. The characteristic of a receiver that specifies the self-generated noise.

A. Noise immunity

B. Noise factor

C. Noise figure

D. Noise margin

135. An FM receiver with an I-F of 10.7 MHz is tuned to 98.7 MHz. What is the numerical value of the image frequency?

A. 77.3 MHz

B. 88.0 MHz

C. 109.4 MHz

D. 120.1 MHz

136. A source of RF interference exists at 109.9 MHz. For which frequency in the FM broadcast band will this be the image frequency?

A. 21.4 MHz

B. 88.5 MHz

C. 99.2 MHz

D. 110.7 MHz

137. The ratio of the superheterodyne receiver response at the desired carrier frequency to that at the image frequency is called

A. The sensitivity

B. The selectivity

C. The image frequency

D. The image rejection ratio

138. The core of an IF transformer usually contains

A. Teflon

B. Computer nylon

C. Powdered iron

D. Laminated steel

139. Shape factor is a measure of

A. Bandwidth

B. Skirt steepness

C. Coupling coefficient

D. Critical coupling

140. _______ is the function which tends to maintain the sound volume level of a voice receiver nearly constant for a large signal strength range.

A. Squelch

B. Muting

C. AGC

D. AFC

141. The function which tends to silence the receiver in the absence of transmitted carrier.

A. Squelch

B. Muting

C. AGC

D. AFC

142. What device is incorporated in a communications receiver to reduce impulse noise?

A. Front-end processor

B. Squelch circuit

C. AGC

D. Noise blanker

143. What type of signal in which a receiver selectivity of 2.4 kHz in the I-F circuitry is optimum?

A. FM voice

B. Double-sideband AM voice

C. FSK data

D. SBB voice

144. If the input to a detector stage is an amplitude-modulated (A3E) IF signal then the output from the stage is

A. A lower frequency carrier

B. The audio voice information

C. A Morse-code signal

D. The upper or lower set of sidebands

145. In a capacitive type, reactance-tube modulator connected across an oscillator tuned circuit, a more negative voltage on the grid of the reactance tube will cause

A. An increase of the oscillator frequency

B. An decrease of oscillator frequency

C. An increase of the reactance-tube capacitance

D. An increase of the reactance tube ac plate current

146. The limiting condition for sensitivity in a communications receiver is

A. The noise floor of the receiver

B. Power supply output ripple

C. The two-tone intermodulation distortion

D. The input impedance to the detector

147. When a communications receiver is tuned to a strong signal, the AGC bias is measured and found to be zero. The fault cannot be caused by a/an

A. Defective IF stage

B. Defective local oscillator

C. Defective RF stage

D. Open circuit in the AGC’s filter capacitor

148. The term used to refer to the condition where the signals from a very strong station are superimposed on other signals being received

A. Cross-modulation interference

B. Intermodulation interference

C. Receiver quieting

D. Capture effect

149. The limiter stage of an FM receiver

A. Behaves as a low-pass filter

B. Limits the amplitude of the IF signal to the required level

C. Behaves as a high-pass filter

D. Behaves as a bandstop filter

150. Motorboating (low-frequency oscillations) in an amplifier can be stopped by

A. Grounding the screen grid

B. Connecting a capacitor between the B+ and lead ground

C. By passing the screen grid resistor with a 0.1 µF capacitor

D. Grounding the plate

Questions and Answers in Modulation Series

Following is the list of multiple choice questions in this brand new series:

Complete List of MCQ in Communications Engineering per topic