CET Communication Systems & RF 2

Question 1

What is the primary advantage of using FM over AM for voice communications?

Accepted Answer

FM provides better noise immunity

Answer

FM is inherently more resistant to amplitude-based noise because information is encoded in frequency variations, not amplitude.

Question 2

Which modulation technique encodes data by shifting the carrier signal's phase between discrete values?

Accepted Answer

PSK

Answer

Phase Shift Keying (PSK) encodes digital data by shifting the carrier phase to represent binary or multi-bit symbols.

Question 3

A transmitter operates at 150 MHz. What is the quarter-wave antenna length?

Accepted Answer

0.5 m

Answer

At 150 MHz, wavelength = 300/150 = 2 m; a quarter-wave element is 2/4 = 0.5 m.

Question 4

What does VSWR of 1:1 indicate in an RF transmission line system?

Accepted Answer

Perfect impedance match with no reflected power

Answer

A VSWR of 1:1 means the source, line, and load impedances are perfectly matched, resulting in zero reflected power.

Question 5

In a superheterodyne receiver, what is the purpose of the IF stage?

Accepted Answer

To convert the signal to a fixed intermediate frequency for consistent filtering

Answer

The IF stage converts the incoming RF signal to a fixed intermediate frequency, allowing stable, high-selectivity filtering regardless of the tuned channel.

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CET Communication Systems & RF 2