How is Forward Error Correction implemented?

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


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

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


Why should phase-shifting of a PSK signal be done at the zero crossing of the RF signal?

  1. To minimize bandwidth
  2. To simplify modulation
  3. To improve carrier suppression
  4. All these choices are correct


What technique minimizes the bandwidth of a PSK31 signal?

  1. Zero-sum character encoding
  2. Reed-Solomon character encoding
  3. Use of sinusoidal data pulses
  4. Use of trapezoidal data pulses


What is the approximate bandwidth of a 13-WPM International Morse Code transmission?

  1. 13 Hz
  2. 26 Hz
  3. 52 Hz
  4. 104 Hz


What is the bandwidth of a 170-hertz shift, 300-baud ASCII transmission?

  1. 0.1 Hz
  2. 0.3 kHz
  3. 0.5 kHz
  4. 1.0 kHz


What is the bandwidth of a 4800-Hz frequency shift, 9600-baud ASCII FM transmission?

  1. 15.36 kHz
  2. 9.6 kHz
  3. 4.8 kHz
  4. 5.76 kHz


How does ARQ accomplish error correction?

  1. Special binary codes provide automatic correction
  2. Special polynomial codes provide automatic correction
  3. If errors are detected, redundant data is substituted
  4. If errors are detected, a retransmission is requested


Which digital code allows only one bit to change between sequential code values?

  1. Binary Coded Decimal Code
  2. Extended Binary Coded Decimal Interchange Code
  3. Excess 3 code
  4. Gray code


How may symbol rate be increased without increasing bandwidth?

  1. It is impossible
  2. Increasing analog-to-digital conversion resolution
  3. Using a more efficient digital code
  4. Using forward error correction


What is the relationship between symbol rate and baud?

  1. They are the same
  2. Baud is twice the symbol rate
  3. Symbol rate is only used for packet-based modes
  4. Baud is only used for RTTY


What factors affect the bandwidth of a transmitted CW signal?

  1. IF bandwidth and Q
  2. Modulation index and output power
  3. Keying speed and shape factor (rise and fall time)
  4. All these choices are correct