Communication Systems Electronics & Communication Engineering MCQ Questions Answers
1) 13 dBm is equivalent to
a) 2 mW
b) 20 W
c) 20 Mw
d) 2 MW
2) A superheterodyne receiver with an IF of 450 kHz is tuned to a signal at 1200 kHz. The image frequency is
3) MCVF telegraphy uses
a) SSB techniques
b) Pulse modulation
c) out-of band signaling
4) If a FET is used as the first AF amplifier in a transistor receiver, this will have the effect of
improving the effectiveness of the AGC
reducing the effect of negative-peak clipping
reducing the effect of noise at low modulation depths
improving the selectivity of the receiver
5) Which of the following pulse modulation is analog ?
b) Differential PCM
6) A 1 MHz sinusoidal carrier is amplitude modulated by a symmetrical square wave of period 100 µsec. Which of the following frequencies will not be present in the modulated signal?
(a) 990 kHz
(c) 1020 kHz
7) The code which provides for parity check is
8) What is the SNR improvement with FSK over ASK in most types of noise environment ?
a) 200 to 300dB
b) 3 to 4dB
c) 10 to 12Db
9) An angle-modulation signal is given by ?(?) = cos(2? × 2 × 106 ? + 2? × 30 sin 150? + 2? × 40 cos 150?) The maximum frequency and phase deviations of s(t) are
(a) 10.5KHz, 140π rad
(b)6 KHz, 80π rad
(c) 10.5 KHz, 100π rad
(d)7.5 KHz, 100π rad
10) In FDM systems used for telephone, which modulation scheme is adopted ?