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Electronics and Communication Engineering - Communication Systems

Exercise : Communication Systems - Section 8
11.
In VHS format each video head is tilted from azimuth by
20°
10°
6°
1°
Answer: Option
Explanation:

Tilting of heads is done to reduce cross-talk.

12.
The number of possible colours with a 4 line digital input monitor are
4
16
64
2
Answer: Option
Explanation:

24 = 16.

13.
Convolution of x(t + 5) with impulse function δ(t - 7) is equal to
x(t - 2)
x(t + 12)
x(t - 12)
(t + 2)
Answer: Option
Explanation:

Convolution of | x(t + s) with d(t - 7)

x(t - 7 + 5) x(t - 2).

14.
Which of the following is a better recording medium?
Ferric oxide
Ferrous oxide
Chromium di oxide
Either (a) or (b)
Answer: Option
Explanation:

Chromium di oxide has very good retentivity.

15.
An angle modulated signal is given by s(t) = cos 2p (2 x 106t + 30 sin 150t + 40 cos 150t). The maximum frequency and phase deviations of s(t) are
10.5 kHz, 140p rad
6 kHz and 80p rad
10.5 kHz, 100p rad
7.5 kHz, 100p rad
Answer: Option
Explanation:

s(t) = cos 2p(2 x 10+16t + 30 sin 150t + 40 cos 150t)

Phase deviation = 100 p

Frequency deviation = 7.5 kHz.

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