Digital Excitement With Computers & Radio Flashcards
E2E01 which type of modulation is common for data emissions below 30MHz?
A. DTMF tones
B. FSK
C. Pulse modulation
D. Spread spectrum
B. FSK
E2E11. What is the difference between direct FSK and audio FSK?
A. Direct FSK applies the data signal to the transmitter VFO
B. Audio FSK has a superior frequency response
C. Direct FSK uses a DC coupled data connection
D. Audio FSK can be performed anywhere in the transmit chain
A. Direct FSK applies the data signal to the transmitter VFO
E4A09. When using a computer’s sound card input to digitize signals, what is the highest frequency signal that can be digitized without aliasing ?
A. The same as the sample rate
B. 1/2 the sample rate
C. 1/10 the sample rate
D. It depends on how the data is stored internally
B. 1/2 the sample rate
E8D07. What is a common cause of overmodulation of AFSK signals?
A. Excessive numbers of retries
B. Ground loops
C. But errors in the modem
D. Excessive transmit audio levels
D. Excessive transmit audio levels
E2E01 Which type of modulation is common for data emissions below 30 MHz?
A. DTMF tones modulating an FM signal
B. FSK
C. Pulse modulation
D. Spread spectrum
B. FSK
E2E11 What is the difference between direct FSK and audio FSK?
A. Direct FSK applies the data signal to the transmitter VFO
B. Audio FSK has a superior frequency response
C. Direct FSK uses a DC-coupled data connection
D. Audio FSK can be performed anywhere in the transmit chain
A. Direct FSK applies the data signal to the transmitter VFO
E4A09 When using a computer’s sound card input to digitize signals, what is the highest frequency signal that can be digitized without aliasing?
A. The same as the sample rate
B. One-half the sample rate
C. One-tenth the sample rate
D. It depends on how the data is stored internally.
B. One-half the sample rate
E8D07 What is a common cause of over modulation of AFSK signals?
A. Excessive numbers of retries
B. Ground loops
C. Bit errors in the modem
D. Excessive transmit audio levels.
D. Excessive transmit audio levels.
E8D06 Which of the following indicates likely over modulation of an AFSK signal such as PSK or MFSK?
A. High reflected power
B. Strong ALC action
C. Harmonics on higher bands
D. Rapid signal fading
B. Strong ALC action
E8D08 What parameter might indicate that excessively high input levels are causing distortion in an AFSK signal?
A. Signal to noise ratio
B. Baud rate
C. Repeat Request Rate (RRR)
D. Intermodulation Distortion (IMD)
D. Intermodulation Distortion (IMD)
E8D09 What is considered a good minimum IMD level for an idling PSK signal?
A. +10dB
B. +15dB
C. -20dB
D. -30dB
D. -30dB
E8C03 When performing phase shift keying, why is it advantageous to shift phase precisely at the zero crossing of the RF carrier?
A. This results in the least possible transmitted bandwidth for the particular mode
B. It is easier to demodulate with a conventional, non-synchronous detector
C. It improves carrier suppression
D. All of these choices are correct
A. This results in the least possible transmitted bandwidth for the particular mode
E2E07 What is the typical bandwidth of a properly modulated MFSK16 signal?
A. 31 Hz
B. 316 Hz
C. 550 Hz
D. 2.16 kHz
B. 316 Hz
E2E06 What is the most common data rate used for HF packet?
A. 48 baud
B. 110 baud
C. 300 baud
D. 1200 baud
C. 300 baud
E8C11 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 used only for packet-based modes
D. Baud is only used for RTTY
A. They are the same
E8C02 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 of a transmitted signal changes to convey information
D. The number of characters carried per second by the station-to-station link
C. The rate at which the waveform of a transmitted signal changes to convey information
E2D09 Which of these digital modes has the fastest data throughput under clear communication conditions?
A. AMTOR
B. 170 Hz shift, 45 baud RTTY
C. PSK31
D. 300 baud packet
D. 300 baud packet
E2E08 Which of the following HF digital modes an be used to transfer binary files?
A. Hellschreiber
B. PACTOR
C. RTTY
D. AMTOR
B. PACTOR
E8D10 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 ode, ASCII has no letters/figures code
B. Baudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 character as a letters/figures shift ode, ASCII has no letters/figures code
C. B. Baudot uses 6 data bits per character, ASCII uses 7 or 8; Baudot has no character as a letters/figures shift ode, ASCII uses 2 letters/figures code
D. Baudot uses 7data bits per character, ASCII uses 8; Baudot has no character as a letters/figures shift ode, ASCII uses 2 letters/figures code
B. Baudot uses 5 data bits per character, ASCII uses 7 or 8; Baudot uses 2 character as a letters/figures shift ode, ASCII has no letters/figures code
E2E02 What doe the letters FEC mean as they relate to digital operations?
A. Forward Error Correction
B. First Error Correction
C. Fatal Error Correction
D. Final Error Correction
A. Forward Error Correction
E8C01 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
C. By transmitting extra data that may be used to detect and correct transmission errors
E8C08 How does ARQ accomplish error corrections?
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
D. If errors are detected, a retransmission is requested
E8C09 Which is the name of a digital code where each preceding or following character changes by only one bit?
A. Binary Coded Decimal Code
B. Extended Binary Coded Decimal Interchange Code
C. Excess 3 code
D. Gray code
D. Gray code
E8C10 What is an advantage of gray code in digital communications where symbols are transmitted as multiple bits?
A. It increases security
B. It has more possible states than simply binary
C. It has more resolution than simple binary
D. It facilitates error detection
D. It facilitates error detection
E8B07 Orthagonal Frequency Division Multiplexing is a technique used for which type of amateur communications?
A. High speed digital modes
B. Extremely low-power contacts
C. EME
D. OFDM signals are not allowed on amateur bands.
A. High speed digital modes
E8B08 What describes Orthogonal Frequency Division Multiplexing?
A. A frequency modulation technique which 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 modulations technique using subcarriers as frequencies chosen to avoid intersymbol interference.
D. A digital modulations technique using subcarriers as frequencies chosen to avoid intersymbol interference.
E2E04 What is indicated when one of the ellipses in an FSK crossed-ellipse display suddenly disappears?
A. Selective fading has occurred
B. One of the signal filters is saturated
C. The receiver has drifted 5 kHz from the desired receive frequency
D. The mark and space signal have been inverted.
A. Selective fading has occurred
