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Subelement M
Communications Technology
Section 82
Types of Transmissions
What term describes a wide-bandwidth communications system in which the RF carrier frequency varies according to some predetermined sequence?
  • Amplitude compandored single sideband.
  • SITOR.
  • Time-domain frequency modulation.
  • Correct Answer
    Spread spectrum communication.
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Name two types of spread spectrum systems used in most RF communications applications?
  • AM and FM.
  • QPSK or QAM.
  • Correct Answer
    Direct Sequence and Frequency Hopping.
  • Frequency Hopping and APSK.
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What is the term used to describe a spread spectrum communications system where the center frequency of a conventional carrier is altered many times per second in accordance with a pseudo-random list of channels?
  • Correct Answer
    Frequency hopping.
  • Direct sequence.
  • Time-domain frequency modulation.
  • Frequency compandored spread spectrum.
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A TDMA radio uses what to carry the multiple conversations sequentially?
  • Separate frequencies.
  • Separate pilot tones.
  • Separate power levels.
  • Correct Answer
    Separate time slots.
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Which of the following statements about SSB voice transmissions is correct?
  • They use A3E emission which are produced by modulating the final amplifier.
  • They use F3E emission which is produced by phase shifting the carrier.
  • Correct Answer
    They normally use J3E emissions, which consists of one sideband and a suppressed carrier.
  • They may use A1A emission to suppress the carrier.
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What are the two most-used PCS (Personal Communications Systems) coding techniques used to separate different calls?
  • QPSK and QAM.
  • Correct Answer
    CDMA and GSM.
  • ABCD and SYZ.
  • AM and Frequency Hopping.

CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are two major radio systems used in cell phones. CDMA is used mostly in the U.S., and GSM is used in the rest of the world.

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