IndiaBIX

Electronics and Communication Engineering - Communication Systems

Exercise : Communication Systems - Section 6
6.
In the television system in India, the odd and even fields are scanned
25 times each
25 times each but alternately
50 times each
50 times each but alternately
Answer: Option
Explanation:

Each field is scanned 25 times but alternately.

7.
Consider the following
  1. A signal f(t) and its Hilbert transform fh(t) have the same energy density spectrum
  2. A signal f(t) and its Hilbert transform, fh(t) have the same auto correlation function
  3. A signal f(t) and its Hilbert transform are mutually orthogonal
Which of the above are true?
1, 2 and 3
1 and 2 only
1 only
2 and 3 only
Answer: Option
Explanation:

All are correct.

8.
Vidicon and plumbicon operate on the principle of
photo conduction
photo emission
photo voltaic
none of the above
Answer: Option
Explanation:

Photo conduction uses the fact that resistivity of some materials depends on intensity of light falling on their surface.

9.
A TV receiver has a width of 60 cm. The aspect ratio is 4/3. The required EHT supply is about
29 kV
2.9 kV
45 kV
4.5 kV
Answer: Option
Explanation:

EHT supply is 1 kV per diagonal inch.

Height = 60 x = 45 cm.

Diagonal = .

10.
The typical squelch circuit
cuts off IF amplifier when AGC is minimum
cuts off IF amplifier when AGC is maximum
cuts off audio amplifier when carrier is absent
eliminates RF interference when signal is weak
Answer: Option
Explanation:

To suppress noise when carrier is absent, squelch circuit cuts off audio amplifier.

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