Electronics and Communication Engineering - Communication Systems

1. 

The output resistance of a microphone is 20 ohms. It is to feed a line of impedance 320 ohms. To ensure maximum power transfer, the turn ratio of transformer is

A. 16
B. 256
C. 2
D. 4

Answer: Option D

Explanation:

(20)(4)2 = 320 ohms.


2. 

In a reactance FET, gm = 9 x 10-3 Siemens, gate to source resistance is one-ninth of reactance of gate to drain capacitor and frequency is 4 MHz. The capacitive-reactance is

A. 1000 Ω
B. 1/1000 Ω
C. 36 x 103 Ω
D. x 103 Ω

Answer: Option A

Explanation:

.


3. 

Audio cassettes used in household tape recorders have a width of

A. 1"
B. 1/2"
C. 1/4"
D. 1/8"

Answer: Option C

Explanation:

Home tape recorders use in (i.e., 6.3 mm) tape having two tracks of 2.5 mm width each with an in between separation of 1.3 mm.


4. 

The receiver of a pulsed RADAR can detect signal power in the order of

A. 1 W
B. 0.1 W
C. 10-5 W
D. 10-12 W

Answer: Option D

Explanation:

It can detect very low power signals.


5. 

In a 100% amplitude modulated signal, the power in the upper sideband when carrier power is to be 100 W and modulation system SSBSC, is

A. 100 W
B. 66 W
C. 50 W
D. 25 W

Answer: Option D

Explanation:

Modulation index = 100% 1

Pc = 100 W


1 2 3 4 5 6 7 8 9 10 Next »