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2013-04-02 00:41:12

study guide only - loosely based reference material for general study and not meant for testing purposes.
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  1. 1. (001) What is one reason for modulation that involves modulating low frequency signals for transmission over long distances?
    c. Ease of radiation.
  2. 2. (001) What are the three general categories used to produce modulation in radio frequency (RF)transmission today?
    c. Amplitude, frequency, and phase.
  3. 3. (002) When the modulating signal and carrier signal are combined within a modulator, the outputsignal contains
    b. carrier, upper sideband, and lower sideband.
  4. 4. (002) If a carrier frequency of 1 MHz and a modulating tone of 10 kHz goes to the modulator, theoutput signal include
    a. 1.01 MHz, 1 MHz, and 0.99 MHz.

  5. 5. (002) The bandwidth of an amplitude modulated signal is
    a. two times the modulating signal.
  6. 6. (002) Use the formula on page 1–3. If an oscilloscope displays a modulation envelope having anEmax of 200 volts and an Emin of 20 volts, what is the modulation percentage?
    a. 81.8.

    %mod -     Emax - Emin / Emax + Emin = )
  7. 7. (002) Which statement concerning bandwidth is true?
    a. Overmodulating increases bandwidth because the distortion produces harmonics.
    b. Undermodulating increases bandwidth because the distortion produces harmonics.
    c. Overmodulating increases bandwidth because the output’s increased amplitude.
    d. Undermodulating increases bandwidth because the output’s decreased amplitude.
    a. Overmodulating increases bandwidth because the distortion produces harmonics.
  8. 8. (003) The output of the oscillator in a frequency modulation (FM) modulator increases infrequency with each.
    a. positive half cycle of the carrier.
  9. 9. (003) In frequency modulation, a significant sideband contains at least what percentage of the total transmitted power?
    a. 1.
  10. 10. (003) What is the formula to find the modulating index?
    a. Deviation divided by frequency of modulation.
  11. 11. (003) A 5 kHz modulating signal has enough peak voltage to cause a deviation of 15 kHz. What isthe modulation index?
    d. 3.
  12. 12. (003) What is it called when a narrow frequency band between adjacent stations preventfrequency modulated sidebands from overlapping?
    b. Guard band.
  13. 13. (004) In phase modulation, what part of the carrier signal is varied?
    d. Phase.
  14. 14. (004) In phase modulation, the carrier’s
    a. phase is shifted at the rate of the modulating signal.
  15. 15. (005) What is the first step in the pulse code modulation process?
    d. The analog signal is band limited.
  16. 16. (005) What part of the pulse code modulation process converts a continuous time signal into adiscrete time signal?
    a. Sampling.
  17. 17. (006) In asynchronous transmissions, what bit is used by the receiving device to verify that the transmission was received correctly?
    b. Parity.
  18. 18. (006) If an error should occur, what transmission is lost in an synchronous transmission?
    b. Block of data.
  19. 19. (007) When using vertical redundancy check, what significance does the amount of ones have in a data bit pattern?
    a. Determines parity.
  20. 20. (007) What error detection method is used for checking a data block greater than 512 and is about 99 percent effective in most applications?
    b. Cyclic redundancy check
  21. 21. (007) When using forward error control as a method of error correction, where does errorcorrection take place?
    a. Receiving end.
  22. 22. (008) Light sources that are applicable to fiber optic waveguide are light-emitting diodes and
    c. semiconductor laser diodes.
  23. 23. (008) What type of light is emitted from a laser?
    b. Coherent.
  24. 24. (009) What are the two main types of photodetectors?
    a. Positive intrinsic negative and avalanche photodiode.
  25. 25. (009) What photo detector converts one photon to one electron?
    c. Positive intrinsic negative diode.