Communication Systems & RF Flashcards
7 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Communication Systems & RF flashcards as text
What is the primary advantage of using FM over AM for voice communications?
Answer: FM provides better noise immunity
FM is inherently more resistant to amplitude-based noise because information is encoded in frequency variations, not amplitude.
Which modulation technique encodes data by shifting the carrier signal's phase between discrete values?
Answer: PSK
Phase Shift Keying (PSK) encodes digital data by shifting the carrier phase to represent binary or multi-bit symbols.
A transmitter operates at 150 MHz. What is the quarter-wave antenna length?
Answer: 0.5 m
At 150 MHz, wavelength = 300/150 = 2 m; a quarter-wave element is 2/4 = 0.5 m.
What does VSWR of 1:1 indicate in an RF transmission line system?
Answer: Perfect impedance match with no reflected power
A VSWR of 1:1 means the source, line, and load impedances are perfectly matched, resulting in zero reflected power.
In a superheterodyne receiver, what is the purpose of the IF stage?
Answer: To convert the signal to a fixed intermediate frequency for consistent filtering
The IF stage converts the incoming RF signal to a fixed intermediate frequency, allowing stable, high-selectivity filtering regardless of the tuned channel.
What is the function of a bandpass filter in an RF communication system?
Answer: Passes a specific range of frequencies while attenuating others
A bandpass filter passes signals within a defined frequency range (passband) and attenuates signals outside it.
Which of the following describes the capture effect in FM receivers?
Answer: The receiver locks onto the stronger of two co-channel signals
The capture effect causes an FM receiver to suppress a weaker co-channel signal and lock onto the stronger signal when both are present.