Deck 18: Communication Devices and Methods

Question 1

In an AM receiver, the output signal from the IF amplifier will have

A)local oscillator minus the modulated carrier
B)local oscillator plus the modulated carrier
C)both A and B
D)only the modulation frequencies

Answer 1

A

Question 2

In an AM or FM receiver, the local oscillator is tuned to the

A)IF + modulation frequency
B)carrier + IF frequency
C)IF frequency
D)carrier frequency

Answer 2

B

Question 3

To create the difference frequency in an AM mixer, the process uses

A)division
B)squaring
C)multiplication
D)summing

Answer 3

C

Question 4

Figure 4 A basic phase- locked loop
Refer to Figure 4. The block with the ? represents the

A)phase detector
B)low- pass filter
C)linear multiplier
D)VCO

Question 5

Both AM and FM receivers have a

A)de- emphasis network
B)limiter
C)local oscillator
D)all of the above

Question 6

In a balanced AM modulator there is

A)only one sideband
B)a carrier and one sideband
C)a carrier and two sidebands
D)only two sidebands

Question 7

To recover the audio from an AM signal, the receiver uses

A)a local oscillator
B)a discriminator
C)AGC
D)none of the above

Question 8

In a linear multiplier, the constant K is a number that is a(n)

A)factor that the inputs are multiplied by to obtain VOUT
B)factor that the inputs are divided by to obtain VOUT
C)amount that is subtracted from an input to obtain VOUT
D)amount that is added to an input to obtain VOUT

Question 9

In an AM receiver, the input signal to the IF amplifier will have

A)local oscillator plus the modulated carrier
B)local oscillator minus the modulated carrier
C)both A and B
D)only the modulation frequencies

Question 10

Before a phase- locked loop (PLL)is locked the VCO is said to be

A)in capture range
B)free- running
C)unlocked
D)in scan mode

Question 11

In general, the capture range of a PLL is

A)less than the lock range
B)greater than the lock range
C)equal to the lock range
D)dependent on the input signal frequency

Question 12

Figure 2 Block diagram for an FM radio receiver
Refer to Figure 2. The block with the ? represents the

A)de- emphasis network
B)IF amplifier
C)audio amplifier
D)limiter

Question 13

The purpose of AGC is to

A)recover the audio signal
B)adjust the amplitude of higher frequency signals
C)suppress noise outside the passband
D)adjust the gain to maintain signal levels

Question 14

A linear four- quadrant multiplier can basically

A)square a negative number by connecting the inputs together
B)square a positive number by connecting the inputs together
C)multiply any two signed numbers
D)all of the above

Question 15

Figure 1 Block diagram for an AM radio receiver
Refer to Figure 1. The block with the ? represents the

A)mixer
B)audio amplifier
C)IF amplifier
D)detector

Question 16

Figure 3
Refer to Figure 3. This circuit is a basic

A)FM demodulator
B)AM demodulator
C)AM modulator
D)FM modulator

Question 17

A fiber optics cable does not have

A)electromagnetic shielding
B)a core
C)cladding
D)jacket

Question 18

Amplitude modulation is essentially a

A)addition process
B)squaring process
C)division process
D)multiplication process

Question 19

When a phase- locked loop is locked, the difference frequency (fi - f0)is

A)twice the VCO frequency
B)equal to the VCO frequency
C)zero or very small
D)none of the above

Question 20

When a phase- locked loop is used as an FM demodulator, the output is the same as the

A)VCO frequency
B)error voltage
C)phase detector output
D)none of the above

Question 21

In an AM receiver, the AGC signal is sent to the audio amplifiers.

Question 22

The RF amplifier in both AM and FM receivers is tuned to

A)the IF frequency
B)the modulation frequency
C)the carrier frequency
D)the local oscillator frequency

Question 23

In an AM receiver, the IF amplifier is designed for a single frequency.

Question 24

The process of modifying a high frequency carrier by a low frequency signal is called

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

Question 25

In a single- sideband system there is a carrier and one sideband.

Question 26

In an AM receiver, the local oscillator generates a 455 kHz frequency.

Question 27

The output of an AM demodulator is only the audio signal.

Question 28

In a phase- locked loop, the phase- detector output is an error voltage.

Question 29

In an FM receiver, recovery of the signal is done with the limiter.

Question 30

Light is transmitted in a fiber optics system primarily by refraction.

Question 31

Transmitting signals with fiber optics is faster than using solid wires.