Communication Systems - Section 1 (2)

Directions to Solve

Communication Systems - Section 1

In sound recording the degree of pre-emphasis is about 6 dB/ octave.

A.	True
B.	False

Answer: Option B

Explanation:

It erases the matter already existing on the tape.

10.

A generator is feeding power to a transmission line of characteristic impedance Z₀. The line is terminated in impedance Z_L. Standing waves will be set up if

A.	ZL = Z0
B.	ZL < Z0
C.	ZL > Z0
D.	both (b) and (c)

Answer: Option D

Explanation:

Both the case, i.e., Z_L > Z₀ and Z_L < Z₀ give rise to standing waves.

11.

Signal to noise ratio of microphone is defined as the ratio of output when the sound pressure is __________ to the output in the absence of any sound signal.

A.	0.5 Pa
B.	0.2 Pa
C.	0.1 Pa
D.	0.01 Pa

Answer: Option C

Explanation:

0.1 Pa (= 0.5 x 10^-4 W/m²) is taken as standard sound pressure for defining S/N ratio of microphones.

12.

Consider the following statements

The amplitude of an FM wave is constant
FM is more immune to noise than AM
FM broadcasts operate in upper VHF and UHF frequency ranges
FM transmitting and receiving equipments are simpler as compared to AM transmitting and receiving equipments

Which of the above are correct?

A.	The amplitude of an FM wave is constant 1, 2, 3, 4
B.	FM is more immune to noise than AM 1, 2, 3
C.	2, 3, 4
D.	1, 3, 4

Answer: Option B

Explanation:

FM equipments are complex as compared to AM equipments.

13.

In a fascimile reproduction time to scan one line is 2 ms. If it has 4% blanking, the visible trace time is

A.	1.92 ms
B.	2.08 ms
C.	50 ms
D.	0.08 ms

Answer: Option A

Explanation:

(2 ms) (1 - 0.04) = 1.92 ms.

14.

Which of the following has the highest input impedance?

A.	CE
B.	CB
C.	CC
D.	Push pull

Answer: Option C

Explanation:

CC connection has very high input impedance and low output impedance.

15.

It is desired that transmission line and load should match for a range of frequencies. The best method is

A.	to use a balun
B.	to use a single stub of adjustable position
C.	to use a double stub
D.	to use a broad band amplifier

Answer: Option C

Explanation:

When matching over a range of frequencies is desired, double stub is necessary.

16.

Frequency shift keying is used mostly in

A.	telegraphy
B.	telephony
C.	satellite communication
D.	radio transmission

Answer: Option A

Explanation:

Frequency shift keying (FSK) is a system of frequency modulation used in telegraphy.

Communication Systems - Section 1 (2)

Communication Systems - Section 1

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