Ham Radio Tech License Part 5

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Ham Radio Tech License Part 5
2011-05-06 00:22:58
Ham Radio Tech License

Study Questions for the Ham Radio Tech License
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  1. What is PSK31?
    A low-rate data transmission mode
  2. What is included in packet transmissions?
    A check sum which permits error detection A header which contains the call sign of the station to which the information is being sent Automatic repeat request in case of error "All of these choices are correct"
  3. What digital code is used when sending CW in the amateur bands?
  4. Which of the following can be used to transmit CW in the amateur bands?
    Straight Key Electronic Keyer Computer Keyboard "All of these choices are correct"
  5. What is a "parity" bit?
    An extra code element used to detect errors in received data
  6. What is a beam antenna?
    An antenna that concentrates signals in one direction
  7. Which of the following is true regarding vertical antennas?
    The electric field is perpendicular to the Earth
  8. Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface?
    A horizontally polarized antenna
  9. What is a disadvantage of the "rubber duck" antenna supplied with most handheld radio transceivers?
    It does not transmit or receive as effectively as a full-sized antenna
  10. How would you change a dipole antenna to make it resonant on a higher frequency?
    Shorten it
  11. What type of antennas are the quad, Yagi, and dish?
    Directional antennas
  12. What is a good reason not to use a "rubber duck" antenna inside your car?
    Signals can be significantly weaker than when it is outside of the vehicle
  13. What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?
  14. What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna?
  15. In which direction is the radiation strongest from a half-wave dipole antenna in free space?
    Broadside to the antenna
  16. What is meant by the gain of an antenna?
    The increase in signal strength in a specified direction when compared to a reference antenna
  17. Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?
    To allow the efficient transfer of power and reduce losses
  18. What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?
    50 ohms
  19. Why is coaxial cable used more often than any other feedline for amateur radio antenna systems?
    It is easy to use and requires few special installation considerations
  20. What does an antenna tuner do?
    It matches the antenna system
    impedance to the transceiver's output impedance
  21. What generally happens as the frequency of a signal passing through coaxial cable is increased?
    The loss increases
  22. Which of the following connectors is most suitable for frequencies above 400 MHz?
    A Type N connector
  23. Which of the following is true of PL-259 type coax connectors?
    The are commonly used at HF frequencies
  24. Why should coax connectors exposed to the weather be sealed against water intrusion?
    To prevent an increase in feedline loss
  25. What might cause erratic changes in SWR readings?
    A loose connection in an antenna or a feedline
  26. What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables?
    RG-8 cable has less loss at a given frequency
  27. Which of the following types of feedline has the lowest loss at VHF and UHF?
    Air-insulated hard line
  28. Which is a commonly accepted value for the lowest voltage that can cause a dangerous electric shock?
    30 volts
  29. How does current flowing through the body cause a health hazard?
    By heating tissue It disrupts the electrical functions of cells It causes involuntary muscle contractions "All of these choices are correct"
  30. What is connected to the green wire in a three-wire electrical AC plug?
    Safety ground
  31. What is the purpose of a fuse in an electrical circuit?
    To interrupt power in case of overload
  32. Why is it unwise to install a 20-ampere fuse in the place of a 5-ampere fuse?
    Excessive current could cause a fire
  33. What is a good way to guard against electrical shock at your station?
    Use three-wire cords and plugs for all AC powered equipment Connect all AC powered station equipment to a common safety ground Use a circuit protected by a ground-fault interrupter "All of these choices are correct"
  34. Which of these precautions should be taken when installing devices for lightning protection in a coaxial cable feedline?
    Ground all of the protectors to a common plate which is in turn connected to an external ground
  35. What is one way to recharge a 12-volt lead-acid station battery if the commercial power is out?
    Connect the battery to a car's battery and run the engine
  36. What kind of hazard is presented by a conventional 12-volt storage battery?
    Explosive gas can collect if not properly vented
  37. What can happen if a lead-acid storage battery is charged or discharged too quickly?
    The battery could overheat and give off flammable gas or explode
  38. Which of the following is good practice when installing ground wires on a tower for lightning protection?
    Ensure that connections are short and direct
  39. What kind of hazard might exist in a power supply when it is turned off and disconnected?
    You might receive an electric shock from stored charge in large capacitors
  40. What safety equipment should always be included in home-built equipment that is powered from 120V AC power circuits?
    A fuse or circuit breaker in series with the AC "hot" conductor
  41. When should members of a tower work team wear a hard hat and safety glasses?
    At all times when any work is being done on the tower
  42. What is a good precaution to observe before climbing an antenna tower?
    Put on a climbing harness and safety glasses
  43. Under what circumstances is it safe to climb a tower without a helper or observer?
  44. Which of the following is an important safety precaution to observe when putting up an antenna tower?
    Look for and stay clear of any overhead electrical wires
  45. What is the purpose of a gin pole?
    To lift tower sections or antennas
  46. What is the minimum safe distance from a power line to allow when installing an antenna?
    So that if the antenna falls unexpectedly, no part of it can come closer than 10 feet to the power wires
  47. Which of the following is an important safety rule to remember when using a crank-up tower?
    This type of tower must never be climbed unless it is in the fully retracted position
  48. What is considered to be a proper grounding method for a tower?
    Separate eight-foot long ground rods for each tower leg, bonded to the tower and each other
  49. Why should you avoid attaching an antenna to a utility pole?
    The antenna could contact high-voltage power wires
  50. Which of the following is true concerning grounding conductors used for lightning protection?
    Sharp bends must be avoided
  51. Which of the following establishes grounding requirements for an amateur radio tower or antenna?
    Local electrical codes
  52. What type of radiation are VHF and UHF radio signals?
    Non-ionizing radiation
  53. Which of the following frequencies has the lowest Maximum Permissible Exposure limit?
    50 MHz
  54. What is the maximum power level that an amateur radio station may use at frequencies above 30 MHz before an RF exposure evaluation is required?
    50 watts PEP at the antenna
  55. What factors affect the RF exposure of people near an amateur station antenna?
    Frequency and power level of the RF field Distance from the antenna to a person Radiation pattern of the antenna "All of these choices are correct"
  56. Why do exposure limits vary with frequency?
    The human body absorbs more RF energy at some frequencies than at others
  57. Which of the following is an acceptable method to determine that your station complies with FCC RF exposure regulations?
    By calculation based on FCC OET Bulletin 65 By calculation based on computer modeling By measurement of field strength using calibrated equipment "All of these choices are correct"
  58. What could happen if a person accidentally touched your antenna while you were transmitting?
    They might receive a painful RF burn
  59. Which of the following actions might amateur operators take to prevent exposure to RF radiation in excess of FCC-supplied limits?
    Relocate antennas
  60. How can you make sure your station stays in compliance with RF safety regulations?
    By re-evaluating the station whenever an item of equipment is changed
  61. Why is duty cycle one of the factors used to determine safe RF radiation exposure levels?
    It affects the average exposure of people to radiation
  62. What is meant by "duty cycle" when referring to RF exposure?
    The ratio of "on" time to "off" time of a transmitted signal