Deck 19: Communications

Question 1

The main difference between an FM receiver and an AM receiver is the method used to recover the audio signal from the

A)mixer.
B)detector.
C)carrier.
D)modulated IF.

Answer 1

D

Question 2

The quadrant classification of a linear multiplier indicates the number of that the multiplier can handle.

A)output polarity combinations
B)input polarity combinations
C)scale factors
D)transfer characteristics

Answer 2

B

Question 3

A mixer is basically a frequency

A)doubler.
B)converter.
C)modulator.
D)demodulator.

Answer 3

B

Question 4

The process of modifying a high frequency carrier by the information to be transmitted is called

A)discrimination.
B)detection.
C)modulation.
D)multiplexing.

Question 5

The IF amplifiers within an FM radio receiver are tuned to

A)455 kHz.
B)100.7 MHz.
C)4.55 MHz.
D)10.7 MHz.

Question 6

A basic IF Amplifier always has

A)a tuned resonant)circuit on both the input and output.
B)a tuned resonant)circuit on the input.
C)a tuned resonant)circuit on the output.
D)None of the above.

Question 7

The phase detector in a PLL is followed by a low- pass filter. The low- pass filter passes the and rejects all other frequencies.

A)difference of the input and feedback signals
B)input signal
C)feedback signal
D)sum of the input and feedback signals

Question 8

The purpose of a balanced modulator is to eliminate

A)both side- bands.
B)the lower side- band.
C)the upper side- band.
D)the carrier.

Question 9

Most VCOs used in PLLs operate on the principle of

A)variable power.
B)variable reactance.
C)variable inductance.
D)phase detection.

Question 10

Combining an audio signal with an RF carrier in a nonlinear device is called

A)modulation.
B)demodulation.
C)filtering.
D)neutralization.

Question 11

The bandwidth of the low- pass filter in a PLL determines the

A)phase difference.
B)capture range.
C)lock range.
D)free- running frequency.

Question 12

For a PLL, the capture range is

A)always greater than the lock range.
B)always two times the lock range.
C)usually less than the lock range.
D)always the same as the lock range.

Question 13

Higher modulating frequencies are amplified more than the lower frequencies at the transmitting end of an FM system by a process called

A)full duplex.
B)filtering.
C)pre- emphasis.
D)de- emphasis.

Question 14

Mixing two signals by a nonlinear process is called

A)bandwidth discrimination.
B)sum and product frequencies.
C)heterodyning.
D)spectrum modulation.

Question 15

The product of two sinusoidal signals is called

A)suppressed- carrier modulation.
B)lower side frequency.
C)balanced modulation.
D)Both A and C above.

Question 16

The signal loss that occurs when photons interact with the molecules of the core in a fiber- optic cable is called

A)absorption.
B)scattering.
C)refraction.
D)scattering.

Question 17

If you receive an AM signal modulated by a pure sinusoidal signal in the audio frequency range, you will hear

A)nothing.
B)distortion.
C)static.
D)a single tone.

Question 18

A phase detector has

A)two input signals and one output signal.
B)three output signals.
C)one input signal and two output signals.
D)no input signals.

Question 19

The outline of the peaks of the modulated carrier has the shape of the information signal, and is called the

A)lower- side frequency.
B)duty cycle.
C)RF index.
D)envelope.

Question 20

In a PLL, to obtain lock, the signal frequency must come within the

A)lock range.
B)capture range.
C)deviation range.
D)closed range.