E2E: Operating HF digital modes; error correction
E2E01:
What is a common method of transmitting data emissions below 30 MHz?
FSK/AFSK
DTMF tones modulating an FM signal
Pulse modulation
Spread spectrum
E2E02:
What do the letters FEC mean as they relate to digital operation?
Forward Error Correction
First Error Correction
Fatal Error Correction
Final Error Correction
E2E03:
How is Forward Error Correction implemented?
By transmitting extra data that may be used to detect and correct transmission errors
By the receiving station repeating each block of three data characters
By transmitting a special algorithm to the receiving station along with the data characters
By varying the frequency shift of the transmitted signal according to a predefined algorithm
E2E04:
What is indicated when one of the ellipses in an FSK crossed-ellipse display suddenly disappears?
Selective fading has occurred
One of the signal filters has saturated
The receiver has drifted 5 kHz from the desired receive frequency
The mark and space signal have been inverted
E2E05:
How does ARQ accomplish error correction?
If errors are detected, a retransmission is requested
Special binary codes provide automatic correction
Special polynomial codes provide automatic correction
If errors are detected, redundant data is substituted
E2E06:
What is the most common data rate used for HF packet communications?
300 baud
48 baud
110 baud
1200 baud
E2E07:
What is the typical bandwidth of a properly modulated MFSK16 signal?
316 Hz
31 Hz
550 Hz
2 kHz
E2E08:
Which of the following HF digital modes can be used to transfer binary files?
PACTOR
Hellschreiber
RTTY
AMTOR
E2E09:
Which of the following HF digital modes uses variable-length coding for bandwidth efficiency?
PSK31
RTTY
PACTOR
MT63
E2E11:
What is the Baudot code?
The International Telegraph Alphabet Number 2 (ITA2) which uses five data bits
A code used to transmit data only in modern computer-based data systems using seven data bits
A binary code consisting of eight data bits
An alternate name for Morse code
E2E12:
Which of these digital communications modes has the narrowest bandwidth?
PSK31
MFSK16
170-Hz shift, 45 baud RTTY
300-baud packet
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