Electronics and Communication Engineering - Communication Systems

41.
An antenna has a resistance of 50 Ω and an equivalent noise resistance of 30 Ω The noise figure in decibels is
1.6 dB
2 dB
3.6 dB
6 dB
Answer: Option
Explanation:

.


42.
An MTI radar operating at 5 GHz has a PRF of 800 pps. The lowest blind speed is
48 m/s
96 m/s
192 m/s
24 m/s
Answer: Option
Explanation:

Lowest blind speed = 800 x 0.06 = 48 m/s.


43.
For maximum output the width of air gap of audio head should be
equal to wavelength
half the wavelength
one quarter the wavelength
very small as compared to wavelength
Answer: Option
Explanation:

When width of air gap is 0.5 1, output is maximum.


44.
The simplest mixer circuit for public address system uses
fixed resistances
variable resistances
inductances
capacitances
Answer: Option
Explanation:

A mixer circuit has variable resistance in series with each microphone to control intensity of sound.


45.
PAM stands for
Phase Angle Modulation
Phase Amplitude Modulation
Pulse Amplitude Modulation
Pulse Angle Modulation
Answer: Option
Explanation:

PAM or pulse amplitude modulation is a system in which signal is sampled at regular intervals and each sample is made proportional to amplitude of the signal at the instant of sampling.