E8 - SIGNALS AND EMISSIONS [4 Exam Questions - 4 Groups] 45 Questions

Question 1

“What is the name of the process that shows that a square wave is made up of a sine wave plus all its odd harmonics?”

A. Fourier analysis
B. Vector analysis
C. Numerical analysis
D. Differential analysis

Answer 1

A. Fourier analysis

Question 2

“Which of the following is a type of analog-to-digital conversion?”

A. Successive approximation
B. Harmonic regeneration
C. Level shifting
D. Phase reversal

Answer 2

A. Successive approximation

Question 3

“What type of wave does a Fourier analysis show to be made up of sine waves of a given fundamental frequency plus all its harmonics?”

A. A sawtooth wave
B. A square wave
C. A sine wave
D. A cosine wave

Answer 3

A. A sawtooth wave

Question 4

“What is “dither” with respect to analog-to-digital converters?”

A. An abnormal condition where the converter cannot settle on a value to represent the signal
B. A small amount of noise added to the input signal to allow more precise representation of a signal over time
C. An error caused by irregular quantization step size
D. A method of decimation by randomly skipping samples

Answer 4

B. A small amount of noise added to the input signal to allow more precise representation of a signal over time

Question 5

“What of the following instruments would be the most accurate for measuring the RMS voltage of a complex waveform?”

A. A grid dip meter
B. A D’Arsonval meter
C. An absorption wave meter
D. A true-RMS calculating meter

Answer 5

D. A true-RMS calculating meter

Question 6

“What is the approximate ratio of PEP-to-average power in a typical single-sideband phone signal?”

A. 2.5 to 1
B. 25 to 1
C. 1 to 1
D. 100 to 1

Answer 6

A. 2.5 to 1

Question 7

“What determines the PEP-to-average power ratio of a single-sideband phone signal?”

A. The frequency of the modulating signal
B. Speech characteristics
C. The degree of carrier suppression
D. Amplifier gain

Answer 7

B. Speech characteristics

Question 8

“Why would a direct or flash conversion analog-to-digital converter be useful for a software defined radio?”

A. Very low power consumption decreases frequency drift
B. Immunity to out-of-sequence coding reduces spurious responses
C. Very high speed allows digitizing high frequencies
D. All these choices are correct

Answer 8

C. Very high speed allows digitizing high frequencies

Question 9

“How many different input levels can be encoded by an analog-to-digital converter with 8-bit resolution?”

A. 8
B. 8 multiplied by the gain of the input amplifier
C. 256 divided by the gain of the input amplifier
D. 256

Answer 9

D. 256

Question 10

“What is the purpose of a low-pass filter used in conjunction with a digital-to-analog converter?”

A. Lower the input bandwidth to increase the effective resolution
B. Improve accuracy by removing out-of-sequence codes from the input
C. Remove harmonics from the output caused by the discrete analog levels generated
D. All these choices are correct

Answer 10

C. Remove harmonics from the output caused by the discrete analog levels generated

Question 11

“Which of the following is a measure of the quality of an analog-to-digital converter?”

A. Total harmonic distortion
B. Peak envelope power
C. Reciprocal mixing
D. Power factor

Answer 11

A. Total harmonic distortion

Question 12

“What is the modulation index of an FM signal?”

A. The ratio of frequency deviation to modulating signal frequency
B. The ratio of modulating signal amplitude to frequency deviation
C. The type of modulation used by the transmitter
D. The bandwidth of the transmitted signal divided by the modulating signal frequency

Answer 12

A. The ratio of frequency deviation to modulating signal frequency

Question 13

“How does the modulation index of a phase-modulated emission vary with RF carrier frequency?”

A. It increases as the RF carrier frequency increases
B. It decreases as the RF carrier frequency increases
C. It varies with the square root of the RF carrier frequency
D. It does not depend on the RF carrier frequency

Answer 13

D. It does not depend on the RF carrier frequency

Question 14

“What is the modulation index of an FM-phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency when the modulating frequency is 1000 Hz?”

A. 3
B. 0.3
C. 3000
D. 1000

Answer 14

A. 3

Question 15

“What is the modulation index of an FM-phone signal having a maximum carrier deviation of plus or minus 6 kHz when modulated with a 2 kHz modulating frequency?”

A. 6000
B. 3
C. 2000
D. 1/3

Answer 15

B. 3

Question 16

“What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus-or-minus 5 kHz when the maximum modulation frequency is 3 kHz?”

A. 60
B. 0.167
C. 0.6
D. 1.67

Answer 16

D. 1.67

Question 17

“What is the deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz when the maximum modulation frequency is 3.5 kHz?”

A. 2.14
B. 0.214
C. 0.47
D. 47

Answer 17

A. 2.14

Question 18

“Orthogonal Frequency Division Multiplexing is a technique used for which type of amateur communication?”

A. High-speed digital modes
B. Extremely low-power contacts
C. EME
D. OFDM signals are not allowed on amateur bands

Answer 18

A. High-speed digital modes

Question 19

“What describes Orthogonal Frequency Division Multiplexing?”

A. A frequency modulation technique that uses non-harmonically related frequencies
B. A bandwidth compression technique using Fourier transforms
C. A digital mode for narrow-band, slow-speed transmissions
D. A digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference

Answer 19

D. A digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference

Question 20

“What is deviation ratio?”

A. The ratio of the audio modulating frequency to the center carrier frequency
B. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency
C. The ratio of the carrier center frequency to the audio modulating frequency
D. The ratio of the highest audio modulating frequency to the average audio modulating frequency

Answer 20

B. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency

Question 21

“What is frequency division multiplexing?”

A. The transmitted signal jumps from band to band at a predetermined rate
B. Two or more information streams are merged into a baseband, which then modulates the transmitter
C. The transmitted signal is divided into packets of information
D. Two or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter

Answer 21

B. Two or more information streams are merged into a baseband, which then modulates the transmitter

Question 22

“What is digital time division multiplexing?”

A. Two or more data streams are assigned to discrete sub-carriers on an FM transmitter
B. Two or more signals are arranged to share discrete time slots of a data transmission
C. Two or more data streams share the same channel by transmitting time of transmission as the sub-carrier
D. Two or more signals are quadrature modulated to increase bandwidth efficiency

Answer 22

B. Two or more signals are arranged to share discrete time slots of a data transmission

Question 23

“How is Forward Error Correction implemented?”

A. By the receiving station repeating each block of three data characters
B. By transmitting a special algorithm to the receiving station along with the data characters
C. By transmitting extra data that may be used to detect and correct transmission errors
D. By varying the frequency shift of the transmitted signal according to a predefined algorithm

Answer 23

C. By transmitting extra data that may be used to detect and correct transmission errors

Question 24

“What is the definition of symbol rate in a digital transmission?”

A. The number of control characters in a message packet
B. The duration of each bit in a message sent over the air
C. The rate at which the waveform changes to convey information
D. The number of characters carried per second by the station-to-station link

Answer 24

C. The rate at which the waveform changes to convey information

Question 25

"Why should phase-shifting of a PSK signal be done at the zero crossing of the RF signal?" A. To minimize bandwidth B. To simplify modulation C. To improve carrier suppression D. All these choices are correct

Answer 25

A. To minimize bandwidth

Question 26

"What technique minimizes the bandwidth of a PSK31 signal?" A. Zero-sum character encoding B. Reed-Solomon character encoding C. Use of sinusoidal data pulses D. Use of trapezoidal data pulses

Answer 26

C. Use of sinusoidal data pulses

Question 27

"What is the approximate bandwidth of a 13-WPM International Morse Code transmission?" A. 13 Hz B. 26 Hz C. 52 Hz D. 104 Hz

Answer 27

C. 52 Hz

Question 28

"What is the bandwidth of a 170-hertz shift, 300-baud ASCII transmission?" A. 0.1 Hz B. 0.3 kHz C. 0.5 kHz D. 1.0 kHz

Answer 28

C. 0.5 kHz

Question 29

"What is the bandwidth of a 4800-Hz frequency shift, 9600-baud ASCII FM transmission?" A. 15.36 kHz B. 9.6 kHz C. 4.8 kHz D. 5.76 kHz

Answer 29

A. 15.36 kHz

Question 30

"How does ARQ accomplish error correction?" A. Special binary codes provide automatic correction B. Special polynomial codes provide automatic correction C. If errors are detected, redundant data is substituted D. If errors are detected, a retransmission is requested

Answer 30

D. If errors are detected, a retransmission is requested

Question 31

"Which digital code allows only one bit to change between sequential code values?" A. Binary Coded Decimal Code B. Extended Binary Coded Decimal Interchange Code C. Excess 3 code D. Gray code

Answer 31

D. Gray code

Question 32

"How may data rate be increased without increasing bandwidth?" A. It is impossible B. Increasing analog-to-digital conversion resolution C. Using a more efficient digital code D. Using forward error correction

Answer 32

C. Using a more efficient digital code

Question 33

"What is the relationship between symbol rate and baud?" A. They are the same B. Baud is twice the symbol rate C. Symbol rate is only used for packet-based modes D. Baud is only used for RTTY

Answer 33

A. They are the same

Question 34

"What factors affect the bandwidth of a transmitted CW signal?" A. IF bandwidth and Q B. Modulation index and output power C. Keying speed and shape factor (rise and fall time) D. All these choices are correct

Answer 34

C. Keying speed and shape factor (rise and fall time)

Question 35

"Why are received spread spectrum signals resistant to interference?" A. Signals not using the spread spectrum algorithm are suppressed in the receiver B. The high power used by a spread spectrum transmitter keeps its signal from being easily overpowered C. The receiver is always equipped with a digital blanker D. If interference is detected by the receiver it will signal the transmitter to change frequencies

Answer 35

A. Signals not using the spread spectrum algorithm are suppressed in the receiver

Question 36

"What spread spectrum communications technique uses a high-speed binary bit stream to shift the phase of an RF carrier?" A. Frequency hopping B. Direct sequence C. Binary phase-shift keying D. Phase compandored spread spectrum

Answer 36

B. Direct sequence

Question 37

"How does the spread spectrum technique of frequency hopping work?" A. If interference is detected by the receiver it will signal the transmitter to change frequencies B. If interference is detected by the receiver it will signal the transmitter to wait until the frequency is clear C. A binary bit stream is used to shift the phase of an RF carrier very rapidly in a pseudorandom sequence D. The frequency of the transmitted signal is changed very rapidly according to a pseudorandom sequence also used by the receiving station

Answer 37

D. The frequency of the transmitted signal is changed very rapidly according to a pseudorandom sequence also used by the receiving station

Question 38

"What is the primary effect of extremely short rise or fall time on a CW signal?" A. More difficult to copy B. The generation of RF harmonics C. The generation of key clicks D. Limits data speed

Answer 38

C. The generation of key clicks

Question 39

"What is the most common method of reducing key clicks?" A. Increase keying waveform rise and fall times B. Low-pass filters at the transmitter output C. Reduce keying waveform rise and fall times D. High-pass filters at the transmitter output

Answer 39

A. Increase keying waveform rise and fall times

Question 40

"What is the advantage of including parity bits in ASCII characters?" A. Faster transmission rate B. The signal can overpower interfering signals C. Foreign language characters can be sent D. Some types of errors can be detected

Answer 40

D. Some types of errors can be detected

Question 41

"What is a common cause of overmodulation of AFSK signals?" A. Excessive numbers of retries B. Ground loops C. Bit errors in the modem D. Excessive transmit audio levels

Answer 41

D. Excessive transmit audio levels

Question 42

"What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels?" A. Signal-to-noise ratio B. Baud rate C. Repeat Request Rate (RRR) D. Intermodulation Distortion (IMD)

Answer 42

D. Intermodulation Distortion (IMD)

Question 43

"What is considered an acceptable maximum IMD level for an idling PSK signal?" A. +10 dB B. +15 dB C. -20 dB D. -30 dB

Answer 43

D. -30 dB

Question 44

"What are some of the differences between the Baudot digital code and ASCII?" A. Baudot uses 4 data bits per character, ASCII uses 7 or 8; Baudot uses 1 character as a letters/figures shift code, ASCII has no letters/figures code B. Baudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 characters as letters/figures shift codes, ASCII has no letters/figures shift code C. Baudot uses 6 data bits per character, ASCII uses 7 or 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes D. Baudot uses 7 data bits per character, ASCII uses 8; Baudot has no letters/figures shift code, ASCII uses 2 letters/figures shift codes

Answer 44

B. Baudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 characters as letters/figures shift codes, ASCII has no letters/figures shift code

Question 45

"What is one advantage of using ASCII code for data communications?" A. It includes built-in error correction features B. It contains fewer information bits per character than any other code C. It is possible to transmit both upper and lower case text D. It uses one character as a shift code to send numeric and special characters

Answer 45

C. It is possible to transmit both upper and lower case text