SUBELEMENT T10

Electrical safety: AC and DC power circuits; antenna installation; RF

hazards

[3 Exam Questions - 3 Groups]

1Electrical Safety 2014

T10A – Power circuits and hazards: hazardous voltages; fuses and circuit breakers; grounding; lightning protection; battery safety; electrical code compliance

T10B – Antenna safety: tower safety; erecting an antenna support; overhead power lines; installing an antenna

T10C - RF hazards: radiation exposure; proximity to antennas; recognized safe power levels; exposure to others; radiation types; duty cycle

2Electrical Safety

 T0A01 - Which of the following is a safety hazard of a 12-volt storage

battery?

A. Touching both terminals with the hands can cause electrical shockB. Shorting the terminals can cause burns, fire, or an explosionC. RF emissions from the batteryD. All of these choices are correct

3Electrical Safety

 T0A01 - Which of the following is a safety hazard of a 12-volt storage

battery?

A. Touching both terminals with the hands can cause electrical shock

B. Shorting the terminals can cause burns, fire, or an explosionC. RF emissions from the batteryD. All of these choices are correct

4Electrical Safety

 T0A02 - How does current flowing through the body cause a health

hazard?

A. By heating tissueB. It disrupts the electrical functions of cellsC. It causes involuntary muscle contractionsD. All of these choices are correct

5Electrical Safety

 T0A02 - How does current flowing through the body cause a health

hazard?

A. By heating tissueB. It disrupts the electrical functions of cellsC. It causes involuntary muscle contractions

D. All of these choices are correct

6Electrical Safety

 T0A03 - What is connected to the green wire in a three-wire electrical AC plug?

A. NeutralB. HotC. Safety groundD. The white wire

7Electrical Safety

 T0A03 - What is connected to the green wire in a three-wire electrical AC plug?

A. NeutralB. Hot

C. Safety groundD. The white wire

8Electrical Safety

 T0A04 - What is the purpose of a

fuse in an electrical circuit?

A. To prevent power supply ripple from damaging a circuitB. To interrupt power in case of overloadC. To limit current to prevent shocksD. All of these choices are correct

9Electrical Safety

 T0A04 - What is the purpose of a

fuse in an electrical circuit?

A. To prevent power supply ripple from damaging a circuit

B. To interrupt power in case of overloadC. To limit current to prevent shocksD. All of these choices are correct

10Electrical Safety

 T0A05 - Why is it unwise to install a 20-ampere fuse in the place of a 5-ampere

fuse?

A. The larger fuse would be likely to blow because it is rated for higher currentB. The power supply ripple would greatly increaseC. Excessive current could cause a fireD. All of these choices are correct

11Electrical Safety

 T0A05 - Why is it unwise to install a 20-ampere fuse in the place of a 5-ampere

fuse?

A. The larger fuse would be likely to blow because it is rated for higher currentB. The power supply ripple would greatly increase

C. Excessive current could cause a fireD. All of these choices are correct

12Electrical Safety

 T0A06 - What is a good way to guard

against electrical shock at your station?

A. Use three-wire cords and plugs for all AC powered equipmentB. Connect all AC powered station equipment to a common safety groundC. Use a circuit protected by a ground-fault interrupterD. All of these choices are correct

13Electrical Safety

 T0A06 - What is a good way to guard

against electrical shock at your station?

A. Use three-wire cords and plugs for all AC powered equipmentB. Connect all AC powered station equipment to a common safety groundC. Use a circuit protected by a ground-fault interrupterD. All of these choices are correct

14Electrical Safety

 T0A07 - Which of these precautions should be

taken when installing devices for lightning protection in a coaxial cable feed line?

A. Include a parallel bypass switch for each protector so that it can be switched out of the circuit when running high powerB. Include a series switch in the ground line of each protector to prevent RF overload from inadvertently damaging the protectorC. Keep the ground wires from each protector separate and connected to station groundD. Ground all of the protectors to a common plate which is in turn connected to an external ground

15Electrical Safety

 T0A07 - Which of these precautions should be

taken when installing devices for lightning protection in a coaxial cable feed line?

A. Include a parallel bypass switch for each protector so that it can be switched out of the circuit when running high powerB. Include a series switch in the ground line of each protector to prevent RF overload from inadvertently damaging the protectorC. Keep the ground wires from each protector separate and connected to station groundD. Ground all of the protectors to a common plate which is in turn connected to an external ground

16Electrical Safety

 T0A08 - What safety equipment should

always be included in home-built equipment that is powered from 120V

AC power circuits?

A. A fuse or circuit breaker in series with the AC hot conductorB. An AC voltmeter across the incoming power sourceC. An inductor in series with the AC power sourceD. A capacitor across the AC power source

17Electrical Safety

 T0A08 - What safety equipment should

always be included in home-built equipment that is powered from 120V

AC power circuits?

A. A fuse or circuit breaker in series with the AC hot conductorB. An AC voltmeter across the incoming power sourceC. An inductor in series with the AC power sourceD. A capacitor across the AC power source

18Electrical Safety

Hydrogen Gas Explosion

19 Safety 2010

 T0A09 - What kind of hazard is

presented by a conventional 12-volt storage battery?

A. It emits ozone which can be harmful to the atmosphereB. Shock hazard due to high voltageC. Explosive gas can collect if not properly ventedD. All of these choices are correct

20Electrical Safety

 T0A09 - What kind of hazard is

presented by a conventional 12-volt storage battery?

A. It emits ozone which can be harmful to the atmosphereB. Shock hazard due to high voltageC. Explosive gas can collect if not properly ventedD. All of these choices are correct

21Electrical Safety

 T0A10 - What can happen if a lead-acid

storage battery is charged or discharged too quickly?

A. The battery could overheat and give off flammable gas or explodeB. The voltage can become reversedC. The memory effect will reduce the capacity of the batteryD. All of these choices are correct

22Electrical Safety

 T0A10 - What can happen if a lead-acid

storage battery is charged or discharged too quickly?

A. The battery could overheat and give off flammable gas or explodeB. The voltage can become reversedC. The memory effect will reduce the capacity of the batteryD. All of these choices are correct

23Electrical Safety

 T0A11 - What kind of hazard might exist in a power supply when it is turned off

and disconnected?

A. Static electricity could damage the grounding systemB. Circulating currents inside the transformer might cause damageC. The fuse might blow if you remove the coverD. You might receive an electric shock from the charged stored in large capacitors

24Electrical Safety

 T0A11 - What kind of hazard might exist in a power supply when it is turned off

and disconnected?

A. Static electricity could damage the grounding systemB. Circulating currents inside the transformer might cause damageC. The fuse might blow if you remove the cover

D. You might receive an electric shock from the charged stored in large capacitors

25Electrical Safety

T10B – Antenna safety

tower safety; erecting an antenna support; overhead power lines; installing an antenna

26Electrical Safety

 T0B01 - When should members of a

tower work team wear a hard hat and safety glasses?

A. At all times except when climbing the towerB. At all times except when belted firmly to the towerC. At all times when any work is being done on the towerD. Only when the tower exceeds 30 feet in height

27Electrical Safety

 T0B01 - When should members of a

tower work team wear a hard hat and safety glasses?

A. At all times except when climbing the towerB. At all times except when belted firmly to the towerC. At all times when any work is being done on the towerD. Only when the tower exceeds 30 feet in height

28Electrical Safety

 T0B02 - What is a good precaution to observe before climbing an antenna

tower?

A. Make sure that you wear a grounded wrist strapB. Remove all tower grounding connectionsC. Put on a climbing harness and safety glassesD. All of the these choices are correct

29Electrical Safety

 T0B02 - What is a good precaution to observe before climbing an antenna

tower?

A. Make sure that you wear a grounded wrist strapB. Remove all tower grounding connectionsC. Put on a climbing harness and safety glassesD. All of the these choices are correct

30Electrical Safety

 T0B03 - Under what circumstances is it safe to climb a tower without a helper

or observer?

A. When no electrical work is being performedB. When no mechanical work is being performedC. When the work being done is not more than 20 feet above the groundD. Never

31Electrical Safety

 T0B03 - Under what circumstances is it safe to climb a tower without a helper

or observer?

A. When no electrical work is being performedB. When no mechanical work is being performedC. When the work being done is not more than 20 feet above the ground

D. Never

32Electrical Safety

 T0B04 - Which of the following is an

important safety precaution to observe when putting up an antenna

tower?

A. Wear a ground strap connected to your wrist at all timesB. Insulate the base of the tower to avoid lightning strikesC. Look for and stay clear of any overhead electrical wiresD. All of these choices are correct

33Electrical Safety

 T0B04 - Which of the following is an

important safety precaution to observe when putting up an antenna

tower?

A. Wear a ground strap connected to your wrist at all timesB. Insulate the base of the tower to avoid lightning strikes

C. Look for and stay clear of any overhead electrical wiresD. All of these choices are correct

34Electrical Safety

 T0B05 - What is the purpose of a gin

pole?

A. To temporarily replace guy wiresB. To be used in place of a safety harnessC. To lift tower sections or antennasD. To provide a temporary ground

35Electrical Safety

 T0B05 - What is the purpose of a gin

pole?

A. To temporarily replace guy wiresB. To be used in place of a safety harnessC. To lift tower sections or antennasD. To provide a temporary ground

36Electrical Safety

 T0B05 - What is the purpose of a gin

pole?

A. To temporarily replace guy wiresB. To be used in place of a safety harness

C. To lift tower sections or antennasD. To provide a temporary ground

37Electrical Safety

38 Safety 2010

Using a Gin Pole

Full body harness

 T0B06 - What is the minimum safe

distance from a power line to allow when installing an antenna?

A. Half the width of your propertyB. The height of the power line above groundC. 1/2 wavelength at the operating frequencyD. So that if the antenna falls unexpectedly, no part of it can come closer than 10 feet to the power wires

39Electrical Safety

 T0B06 - What is the minimum safe

distance from a power line to allow when installing an antenna?

A. Half the width of your propertyB. The height of the power line above groundC. 1/2 wavelength at the operating frequency

D. So that if the antenna falls unexpectedly, no part of it can come closer than 10 feet to the power wires

40Electrical Safety

 T0B07 - Which of the following is an important safety rule to remember when using a crank-

up tower?

A. This type of tower must never be paintedB. This type of tower must never be groundedC. This type of tower must never be climbed unless it is in the fully retracted positionD. All of these choices are correct

41Electrical Safety

 T0B07 - Which of the following is an important safety rule to remember when using a crank-

up tower?

A. This type of tower must never be paintedB. This type of tower must never be groundedC. This type of tower must never be climbed unless it is in the fully retracted positionD. All of these choices are correct

42Electrical Safety

43 Safety 2014

Crank Up Towers

 T0B08 - What is considered to be a

proper grounding method for a tower?

A. A single four-foot ground rod, driven into the ground no more than 12 inches from the baseB. A ferrite-core RF choke connected between the tower and groundC. Separate eight-foot long ground rods for each tower leg, bonded to the tower and each otherD. A connection between the tower base and a cold water pipe

44Electrical Safety

 T0B08 - What is considered to be a

proper grounding method for a tower?

A. A single four-foot ground rod, driven into the ground no more than 12 inches from the baseB. A ferrite-core RF choke connected between the tower and groundC. Separate eight-foot long ground rods for each tower leg, bonded to the tower and each otherD. A connection between the tower base and a cold water pipe

45Electrical Safety

46Electrical Safety

Tower Base and Grounding

Ground rods are 8 foot long and bonded together

 T0B09 - Why should you avoid attaching

an antenna to a utility pole?

A. The antenna will not work properly because of induced voltagesB. The utility company will charge you an extra monthly feeC. The antenna could contact high-voltage power wiresD. All of these choices are correct

47Electrical Safety

 T0B09 - Why should you avoid attaching

an antenna to a utility pole?

A. The antenna will not work properly because of induced voltagesB. The utility company will charge you an extra monthly feeC. The antenna could contact high-voltage power wiresD. All of these choices are correct

48Electrical Safety

 T0B10 - Which of the following is true

concerning grounding conductors used for lightning protection?

A. Only non-insulated wire must be usedB. Wires must be carefully routed with precise right-angle bendsC. Sharp bends must be avoidedD. Common grounds must be avoided

49Electrical Safety

 T0B10 - Which of the following is true

concerning grounding conductors used for lightning protection?

A. Only non-insulated wire must be usedB. Wires must be carefully routed with precise right-angle bends

C. Sharp bends must be avoidedD. Common grounds must be avoided

50Electrical Safety

 T0B11 - Which of the following

establishes grounding requirements for an amateur radio tower or antenna?

A. FCC Part 97 RulesB. Local electrical codesC. FAA tower lighting regulationsD. Underwriters Laboratories' recommended practices

51Electrical Safety

 T0B11 - Which of the following

establishes grounding requirements for an amateur radio tower or antenna?

A. FCC Part 97 Rules

B. Local electrical codesC. FAA tower lighting regulationsD. Underwriters Laboratories' recommended practices

52Electrical Safety

 T0B12 - Which of the following is good

practice when installing ground wires on a tower for lightning protection?

A. Put a loop in the ground connection to prevent water damage to the ground systemB. Make sure that all bends in the ground wires are clean, right angle bendsC. Ensure that connections are short and directD. All of these choices are correct

53Electrical Safety

 T0B12 - Which of the following is good

practice when installing ground wires on a tower for lightning protection?

A. Put a loop in the ground connection to prevent water damage to the ground systemB. Make sure that all bends in the ground wires are clean, right angle bendsC. Ensure that connections are short and directD. All of these choices are correct

54Electrical Safety

T10C - RF hazards

radiation exposure; proximity to antennas; recognized safe power

levels; exposure to others; radiation types; duty cycle

55Electrical Safety

 T0C01 - What type of radiation are VHF

and UHF radio signals?

A. Gamma radiationB. Ionizing radiationC. Alpha radiationD. Non-ionizing radiation

56Electrical Safety

 T0C01 - What type of radiation are VHF

and UHF radio signals?

A. Gamma radiationB. Ionizing radiationC. Alpha radiation

D. Non-ionizing radiation

57Electrical Safety

 T0C02 - Which of the following frequencies

has the lowest value for Maximum Permissible Exposure limit?

A. 3.5 MHzB. 50 MHzC. 440 MHzD. 1296 MHz

58Electrical Safety

 T0C02 - Which of the following frequencies

has the lowest value for Maximum Permissible Exposure limit?

A. 3.5 MHz

B. 50 MHzC. 440 MHzD. 1296 MHz

59Electrical Safety

60

Band (Wavelength)

Transmitter Power (Watts)

160 m 50075 m 50080 m 50040 m 50030 m 42520 m 22517 m 12515 m 10012 m 7510 m 50

6 - 1.23 m 5070 cm 7033 cm 15023 cm 200

13 cm and up 250

Power Thresholds for Routine Evaluation

60Safety 2010

The FCC requires a station RF safety evaluation if these power levels are exceeded

Note power level varies by band because the human body is more sensitive (Specific Absorption Rate or SAR) to some frequencies than others

61Safety 2014

Duty Cycle

Mode Duty CycleCW Morse telegraphy 40%

SSB voice 20%

SSB voice, heavy speech processing 50%

SSB AFSK 100%

SSB SSTV 100%

FM voice or data 100%

FSK 100%

AM voice, 50% modulation 50%

AM voice, 100% modulation 30%

Duty cycle refers to both the transmit vs. receive time and the average power level during transmission. Because CW has gaps between symbols the average power is less than 100%. SSB power output varies with modulation. FM is full power regardless of modulation.

Time Averaged Exposure Calculations

62 G0 - RF Safety

The FCC averages RF exposure times over a 10 and 30 minute periods. These graphs show the same exposure amount whether long, low-level or short, high-level. Lower duty cycle modes cause lower exposures.

 T0C03 - What is the maximum power level that an amateur radio station may use at VHF frequencies before an RF exposure

evaluation is required?

A. 1500 watts PEP transmitter outputB. 1 watt forward powerC. 50 watts PEP at the antennaD. 50 watts PEP reflected power

63Electrical Safety

 T0C03 - What is the maximum power level that an amateur radio station may use at VHF frequencies before an RF exposure

evaluation is required?

A. 1500 watts PEP transmitter outputB. 1 watt forward power

C. 50 watts PEP at the antennaD. 50 watts PEP reflected power

64Electrical Safety

 T0C04 - What factors affect the RF

exposure of people near an amateur station antenna?

A. Frequency and power level of the RF fieldB. Distance from the antenna to a personC. Radiation pattern of the antennaD. All of these choices are correct

65Electrical Safety

 T0C04 - What factors affect the RF

exposure of people near an amateur station antenna?

A. Frequency and power level of the RF fieldB. Distance from the antenna to a personC. Radiation pattern of the antenna

D. All of these choices are correct

66Electrical Safety

 T0C05 - Why do exposure limits vary

with frequency?

A. Lower frequency RF fields have more energy than higher frequency fieldsB. Lower frequency RF fields do not penetrate the human bodyC. Higher frequency RF fields are transient in natureD. The human body absorbs more RF energy at some frequencies than at others

67Electrical Safety

 T0C05 - Why do exposure limits vary

with frequency?

A. Lower frequency RF fields have more energy than higher frequency fieldsB. Lower frequency RF fields do not penetrate the human bodyC. Higher frequency RF fields are transient in nature

D. The human body absorbs more RF energy at some frequencies than at others

68Electrical Safety

 T0C06 - Which of the following is an

acceptable method to determine that your station complies with FCC RF

exposure regulations?A. By calculation based on FCC OET Bulletin 65B. By calculation based on computer modelingC. By measurement of field strength using calibrated equipmentD. All of these choices are correct

69Electrical Safety

 T0C06 - Which of the following is an

acceptable method to determine that your station complies with FCC RF

exposure regulations?A. By calculation based on FCC OET Bulletin 65B. By calculation based on computer modelingC. By measurement of field strength using calibrated equipment

D. All of these choices are correct

70Electrical Safety

 T0C07 - What could happen if a person

accidentally touched your antenna while you were transmitting?

A. Touching the antenna could cause television interferenceB. They might receive a painful RF burnC. They might develop radiation poisoningD. All of these choices are correct

71Electrical Safety

 T0C07 - What could happen if a person

accidentally touched your antenna while you were transmitting?

A. Touching the antenna could cause television interference

B. They might receive a painful RF burnC. They might develop radiation poisoningD. All of these choices are correct

72Electrical Safety

 T0C08 - Which of the following actions

might amateur operators take to prevent exposure to RF radiation in

excess of FCC-supplied limits?

A. Relocate antennasB. Relocate the transmitterC. Increase the duty cycleD. All of these choices are correct

73Electrical Safety

 T0C08 - Which of the following actions

might amateur operators take to prevent exposure to RF radiation in

excess of FCC-supplied limits?

A. Relocate antennasB. Relocate the transmitterC. Increase the duty cycleD. All of these choices are correct

74Electrical Safety

 T0C09 - How can you make sure your station stays in compliance with RF

safety regulations?

A. By informing the FCC of any changes made in your stationB. By re-evaluating the station whenever an item of equipment is changedC. By making sure your antennas have low SWRD. All of these choices are correct

75Electrical Safety

 T0C09 - How can you make sure your station stays in compliance with RF

safety regulations?

A. By informing the FCC of any changes made in your stationB. By re-evaluating the station whenever an item of equipment is changedC. By making sure your antennas have low SWRD. All of these choices are correct

76Electrical Safety

 T0C10 - Why is duty cycle one of the

factors used to determine safe RF radiation exposure levels?

A. It affects the average exposure of people to radiationB. It affects the peak exposure of people to radiationC. It takes into account the antenna feed line lossD. It takes into account the thermal effects of the final amplifier

77Electrical Safety

 T0C10 - Why is duty cycle one of the factors

used to determine safe RF radiation exposure levels?

A. It affects the average exposure of people to radiationB. It affects the peak exposure of people to radiationC. It takes into account the antenna feed line lossD. It takes into account the thermal effects of the final amplifier

78Electrical Safety

 T0C11 - What is the definition of duty cycle during the averaging time for RF

exposure?

A. The difference between the lowest power output and the highest power output of a transmitterB. The difference between the PEP and average power output of a transmitterC. The percentage of time that a transmitter is transmittingD. The percentage of time that a transmitter is not transmitting

79Electrical Safety

 T0C11 - What is the definition of duty cycle during the averaging time for RF

exposure?

A. The difference between the lowest power output and the highest power output of a transmitterB. The difference between the PEP and average power output of a transmitterC. The percentage of time that a transmitter is transmittingD. The percentage of time that a transmitter is not transmitting

80Electrical Safety

 T0C12 - How does RF radiation differ

from ionizing radiation (radioactivity)?

A. RF radiation does not have sufficient energy to cause genetic damageB. RF radiation can only be detected with an RF dosimeterC. RF radiation is limited in range to a few feetD. RF radiation is perfectly safe

81Electrical Safety

 T0C12 - How does RF radiation differ

from ionizing radiation (radioactivity)?

A. RF radiation does not have sufficient energy to cause genetic damageB. RF radiation can only be detected with an RF dosimeterC. RF radiation is limited in range to a few feetD. RF radiation is perfectly safe

82Electrical Safety

 T0C13 - If the averaging time for exposure is 6 minutes, how much power density is permitted if the signal is present for 3 minutes and absent for 3 minutes rather than being present for the

entire 6 minutes?

A. 3 times as muchB. 1/2 as muchC. 2 times as muchD. There is no adjustment allowed for shorter exposure times

83Electrical Safety

 T0C13 - If the averaging time for exposure is 6 minutes, how much power density is permitted if the signal is present for 3 minutes and absent for 3 minutes rather than being present for the

entire 6 minutes?

A. 3 times as muchB. 1/2 as much

C. 2 times as muchD. There is no adjustment allowed for shorter exposure times

84Electrical Safety

End ofSUBELEMENT T10

Electrical safety: AC and DC power circuits; antenna installation; RF

hazards

85Electrical Safety