ECE 433 (Project Study and Practicum)
Assignment #1 (49-58)
Group Members:
Agcio, Ryan
Alamay, Janno Gift
Bolhayon, Ryniel
Chullar, Elvis
Diawan, Louie
Im-motna, Ryan
Mangangey, Felbon
Paciteng, Arnel
Salming, Jason
49). Show which of the following statements about the amplitude limiter is true:
a) The circuit is always biased in class C, by virtue of the leak-type bias.
b) When the input increases past the threshold of limiting, the gain decreases to keep the output
constant.
c) The output must be tuned.
d) Leak-type bias must be used.
*Ans.: a) The circuit is always biased in class C, by virtue of the leak-type bias.
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 683 & 719)
50) In a radio receiver with simple AGC
a) an increase in signal strength produces more AGC
b) the audio stage gain is normally controlled by the AGC
c) the faster the AGC time constant, the more accurate the output
d) the highest AGC voltage is produced between stations
*Ans.: a) an increase in signal strength produces more AGC
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 683 & 719)
51) In a broadcast superheterodyne receiver, the
a) local oscillator operates below the signal frequency
b) mixer input must be tuned to the signal frequency
c) local oscillator frequency is normally doubled the IF
d) RF amplifier normally works at 455 khz above the carrier frequency
*Ans.: b) mixer input must be tuned to the signal frequency
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 683 & 719)
52) To prevent overloading of the last IF amplifier in receiver, one should use
a) squelch
b) variable sensitivity
c) variable selectivity
d) double conversion
*Ans.: b) variable sensitivity
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 683 & 719)
53) A superheterodyne receiver with an IF of 450 khz is tuned to a signal at 1200 khz. The image frequency
is
a) 750 khz
b) 900 khz
c) 1650 khz
d) 2100 khz
*Ans.: d)2100 khz
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 684 & 719)
54) In a ratio detector
a) the linearity is worse than in a phase discriminator
b) stabilization against signal strength variations is provided
c) the output is twice that obtainable from a similar phase discriminator
d) the circuit is the same as in discriminator, except that the diodes are reversed
*Ans.: a) the linearity is worse than in a phase discriminator
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 684 & 719)
55) The typical squelch circuit
a) cuts off an audio amplifier when the carrier is absent
b) eliminates the RF interference when the signal is weak
c) cuts off an IF amplifier when AGC is maximum
d) cuts off an IF amplifier when the AGC is minimum
*Ans.: a) cuts off an audio amplifier when the carrier is absent
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 684 & 719)
56) Indicate the false statement in connection with communications receivers
a) The noise limiter cuts off the receiver’s output during a noise pulse
b) A product demodulator could be used for the reception of Morse code
c) Double conversion is used to improve image rejection
d) variable sensitivity is used to eliminate selective fading
*Ans.: d) variable sensitivity is used to eliminate selective fading
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 684 & 719)
57) Indicate which of the following circuits could not demodulate SSB:
a) Balanced modulator
b) Product detector
c) BFO
d) Phase discriminator
*Ans.: d) Phase discriminator
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 684 & 719)
58) If an FET is used as the first AF amplifier in a transistor receiver, this will have the effect of
a) improving the effectiveness of the AGC
b) reducing the effect of negative-peak clipping
c) reducing the effect of noise at low modulation depths
d) improving the selectivity of the receiver
*Ans.: b) reducing the effect of negative-peak clipping
Reference: Electronic Communication Systems 3rd edition
Author: Kennedy (page 685 & 719)