Question 1

The main function of a balanced modulator is to

Accepted Answer

A) produce balanced modulation of a carrier wave 
B) produce 100% modulation 
C) suppress carrier signal in order to create a single-sideband or double sideband 
D) limit noise picked by a receiver B

Question 2

In TV systems, equalising pulses are sent during

Accepted Answer

A) horizontal blanking 
B) vertical blanking 
C) serrations 
D) horizontal retrace A

Question 3

A three stage telephone switching structure is to have 128 input and 128 output terminals. There are 16 first stage and 16 third stage matrices. To avoid blocking the number of intermediate paths required is

Accepted Answer

A) 16 
B) 15 
C) 8 
D) 1 B

Question 4

For a plate-modulated class C amplifier the plate supply voltage is E. The maximum plate cathode voltage could be almost high as

Accepted Answer

A) 2e 
B) 3e 
C) 4e 
D) 6e

Question 5

In a TV receiver antenna the length of reflector rod.

Accepted Answer

A) is the same as that of dipole 
B) is less than that of dipole 
C) is more than that of dipole 
D) may be equal, more or less than that of dipole

Question 6

The modulation index of an FM is changed from 0 to 1. How does the transmitted power change?

Accepted Answer

A) gets halved 
B) gets doubled 
C) gets increased by 50 percent 
D) remains unchanged

Question 7

For AM receivers the standard IF frequency is

Accepted Answer

A) 106 khz 
B) 455 khz 
C) 1.07 mhz 
D) 10.7 mhz

Exam 4: Electronics and Telecommunications