E0 Safety

E0A Safety: RF radiation hazards; hazardous materials; grounding

1. E0A01

   What is the primary function of an external earth connection or ground rod?

   1. A. Prevent static build up on power lines
   2. B. Lightning charge dissipation
   3. C. Reduce RF current flow between pieces of equipment
   4. D. Protect breaker panel from power surges
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   B. Lightning charge dissipation

   An external ground rod connects the station's lightning protection to earth, giving lightning current a low-impedance path to dissipate into the soil outside the building. Its primary job is safety from lightning, not RF performance.

   • A. Static on power lines is the electric utility's concern; a station ground rod is not installed for that.
   • C. RF current between pieces of equipment is reduced by bonding the equipment together with short, wide conductors, not by a ground rod.
   • D. Surge protection for a breaker panel comes from the electrical service ground and surge protective devices, not from the station's ground rod.

2. E0A02

   When evaluating RF exposure levels from your station at a neighbor’s home, what must you do?

   1. A. Ensure signals from your station are less than the controlled maximum permissible exposure (MPE) limits
   2. B. Ensure signals from your station are less than the uncontrolled maximum permissible exposure (MPE) limits
   3. C. Ensure signals from your station are less than the controlled maximum permissible emission (MPE) limits
   4. D. Ensure signals from your station are less than the uncontrolled maximum permissible emission (MPE) limits
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   B. Ensure signals from your station are less than the uncontrolled maximum permissible exposure (MPE) limits

   Under 47 CFR 97.13(c)(1), exposure of nearby people who are not members of the licensee's household must be evaluated against the general population/uncontrolled maximum permissible exposure (MPE) limits in 47 CFR 1.1310. Neighbors cannot be assumed to know about or control their exposure, so the stricter uncontrolled limits apply.

   • A. Under 97.13(c)(1), controlled (occupational) limits may be applied to members of the licensee's immediate household who have the appropriate training and information, not to neighbors.
   • C. MPE stands for maximum permissible exposure, not emission, and controlled limits do not apply to neighbors.
   • D. Uncontrolled limits are correct for neighbors, but MPE stands for maximum permissible exposure, not emission.

3. E0A03

   Over what range of frequencies are the FCC human body RF exposure limits most restrictive?

   1. A. 300 kHz - 3 MHz
   2. B. 3 - 30 MHz
   3. C. 30 - 300 MHz
   4. D. 300 - 3000 MHz
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   C. 30 - 300 MHz

   The human body absorbs RF energy most efficiently near its whole-body resonant frequencies, which fall in the 30 to 300 MHz range. Table 1 of 47 CFR 1.1310 sets the lowest power density limits there: 0.2 mW/cm² for general population/uncontrolled exposure and 1.0 mW/cm² for occupational/controlled exposure.

   • A. From 0.3 to 3 MHz the uncontrolled limit is much higher: 100 mW/cm² up to 1.34 MHz, then 180/f² (about 20 mW/cm² at 3 MHz).
   • B. From 3 to 30 MHz the uncontrolled limit (180/f²) falls from 20 mW/cm² to 0.2 mW/cm², reaching the 30 to 300 MHz value only at 30 MHz.
   • D. From 300 to 1500 MHz the uncontrolled limit (f/1500) rises from 0.2 to 1.0 mW/cm², and it stays at 1.0 mW/cm² above that, so the range is less restrictive than 30 to 300 MHz.

4. E0A04

   When evaluating a site with multiple transmitters operating at the same time, the operators and licensees of which transmitters are responsible for mitigating over-exposure situations?

   1. A. Each transmitter that produces 20 percent or more of its MPE limit in areas where the total MPE limit is exceeded
   2. B. Each transmitter operating with a duty cycle greater than 25 percent
   3. C. Each transmitter that produces 5 percent or more of its MPE limit in areas where the total MPE limit is exceeded
   4. D. Each transmitter operating with a duty cycle greater than 50 percent
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   C. Each transmitter that produces 5 percent or more of its MPE limit in areas where the total MPE limit is exceeded

   Under 47 CFR 1.1307(b)(5)(i), when the exposure limits are exceeded in an accessible area because of several fixed transmitters, bringing the area into compliance is the shared responsibility of every licensee whose transmitter produces more than 5 percent of the applicable exposure limit (in terms of power) at that location.

   • A. The threshold in 1.1307(b)(5)(i) is 5 percent of the exposure limit, not 20 percent.
   • B. Responsibility is based on each transmitter's contribution to exposure (more than 5 percent of the limit), not on duty cycle.
   • D. Responsibility is based on each transmitter's contribution to exposure (more than 5 percent of the limit), not on duty cycle.

5. E0A05

   What hazard is created by operating at microwave frequencies?

   1. A. Microwaves are ionizing radiation
   2. B. The high gain antennas commonly used can result in high exposure levels
   3. C. Microwaves are in the frequency range where wave velocity is higher
   4. D. The extremely high frequency energy can damage the joints of antenna structures
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   B. The high gain antennas commonly used can result in high exposure levels

   Microwave stations often use high-gain antennas such as dishes, which concentrate the transmitter's power into a narrow beam. Power density in front of such an antenna can exceed exposure limits even when the transmitter power is modest.

   • A. Microwaves are non-ionizing radiation; ionizing radiation (such as X-rays) is at far higher frequencies.
   • C. All radio waves travel at the same speed in free space, whatever their frequency.
   • D. Microwave energy does not damage the joints of antenna structures.

6. E0A06

   Why are there separate electric (E) and magnetic (H) MPE limits at frequencies below 300 MHz?

   1. A. The body reacts to electromagnetic radiation from both the E and H fields
   2. B. Ground reflections and scattering cause the field strength to vary with location
   3. C. E field and H field radiation intensity peaks can occur at different locations
   4. D. All these choices are correct
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   D. All these choices are correct

   Below 300 MHz, Table 1 of 47 CFR 1.1310 gives separate electric field (V/m) and magnetic field (A/m) limits. At these frequencies people are often in the near field of an antenna, where the ratio of the two fields is not fixed: the body responds to each, reflections and scattering make them vary from place to place, and their peaks can occur at different locations, so each field must be checked.

   • A. True: the body absorbs energy from both the electric and the magnetic field, but this is only one of the reasons.
   • B. True: ground reflections and scattering make field strength vary with location, but this is only one of the reasons.
   • C. True: electric and magnetic field peaks can occur at different locations, so both must be measured, but this is only one of the reasons.

7. E0A07

   What is meant by “100% tie-off” regarding tower safety?

   1. A. All loose ropes and guys secured to a fixed structure
   2. B. At least one lanyard attached to the tower at all times
   3. C. All tools secured to the climber’s harness
   4. D. All circuit breakers feeding power to the tower must be tied closed with tape, cable, or ties
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   B. At least one lanyard attached to the tower at all times

   100% tie-off means the climber is attached to the tower by at least one lanyard at every moment. Climbers carry two lanyards, or a lanyard plus a climbing safety system, and connect the second before releasing the first when moving past an obstacle.

   • A. Securing loose ropes and guys is good housekeeping but does not keep the climber attached to the tower.
   • C. Tool lanyards keep tools from falling but do not protect the climber from a fall.
   • D. Securing the power to a tower is a lockout/tagout practice, not tie-off.

8. E0A08

   What does SAR measure?

   1. A. Signal attenuation ratio
   2. B. Signal amplification rating
   3. C. The rate at which RF energy is absorbed by the body
   4. D. The rate of RF energy reflected from stationary terrain
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   C. The rate at which RF energy is absorbed by the body

   SAR (specific absorption rate) is the rate at which the body absorbs RF energy, in watts per kilogram of tissue. Under 47 CFR 1.1310(c), the general population/uncontrolled limits are 0.08 W/kg averaged over the whole body and 1.6 W/kg peak over any 1 gram of tissue.

   • A. SAR stands for specific absorption rate, not signal attenuation ratio.
   • B. SAR stands for specific absorption rate, not a signal amplification rating.
   • D. SAR measures energy absorbed by the body, not energy reflected from terrain.

9. E0A09

   Which of the following types of equipment are exempt from RF exposure evaluations?

   1. A. Transceivers with less than 7 watts of RF output
   2. B. Antennas that radiate only in the near field
   3. C. Hand-held transceivers sold before May 3, 2021
   4. D. Dish antennas less than one meter in diameter
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   C. Hand-held transceivers sold before May 3, 2021

   The FCC's revised RF exposure rules took effect for amateur stations on May 3, 2021, and the question pool treats hand-held transceivers sold before that date as exempt from evaluation. Otherwise, exemptions under 47 CFR 1.1307(b)(3) depend on power or ERP, frequency, and distance from people, not on a fixed power rating or an antenna type.

   • A. There is no fixed 7-watt exemption; under 1.1307(b)(3)(i)(C) the exempt ERP threshold depends on frequency and distance from people.
   • B. Every antenna has a near field, and exposure close to an antenna can be high; the table exemption in 1.1307(b)(3)(i)(C) applies only at distances of at least λ/2π.
   • D. There is no exemption based on dish size; even a small dish concentrates power into a beam that can create high exposure.

10. E0A10

    When must an RF exposure evaluation be performed on an amateur station operating on 80 meters?

    1. A. An evaluation must always be performed
    2. B. When the ERP of the station is less than 10 watts
    3. C. When the station’s operating mode is CW
    4. D. When the output power from the transmitter is less than 100 watts
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    A. An evaluation must always be performed

    Under 47 CFR 1.1307(b)(1)(i) and 97.13(c)(1), every amateur station must be assessed: the licensee either shows by the calculation in 1.1307(b)(3) that the station is exempt (paragraph (b)(1)(i)(A)) or prepares an evaluation against the 1.1310 limits (paragraph (b)(1)(i)(B)). The 2021 rule changes removed the amateur service's former blanket exemptions based on power level, so for an 80 meter station the evaluation must always be done.

    • B. Low ERP makes an exemption more likely; it is not what triggers the requirement to evaluate the station.
    • C. Mode affects the duty cycle used in the calculation, but CW does not trigger or excuse an evaluation.
    • D. Low transmitter power does not trigger an evaluation; the requirement applies to an 80 meter station whether it runs more or less than 100 W.

11. E0A11

    To what should lanyards be attached while climbing?

    1. A. Antenna mast
    2. B. Guy brackets
    3. C. Tower rungs
    4. D. Tower legs
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    D. Tower legs

    Lanyards should be attached to the tower legs, the main structural members that carry the tower's load. They are the strongest anchor points available to a climber.

    • A. The antenna mast is a separate pipe that can bend or pull loose; it is not a fall-arrest anchor.
    • B. Guy brackets are attachment points for the guy wires, not anchors for a climber's lanyard.
    • C. Rungs and cross braces are lighter members than the legs and are not the recommended anchor for fall arrest.

12. E0A12

    Where should a shock-absorbing lanyard be attached to a tower when working above ground?

    1. A. Above the climber’s head level
    2. B. To the belt of the fall-arrest harness
    3. C. Even with the climber's waist
    4. D. To the next lowest set of guys
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    A. Above the climber’s head level

    Anchoring the lanyard above head level keeps the free-fall distance short if the climber slips, so the lanyard stops the fall sooner. The shock absorber then spreads out the stopping force to reduce injury.

    • B. One end of the lanyard connects to the harness, but the tower end must be anchored above the head; the harness belt is not an anchor on the tower.
    • C. Anchoring at waist level allows a longer free fall before the lanyard catches than anchoring above the head.
    • D. Guys below the climber would allow a long fall before the lanyard catches, and guy attachment points are not fall-arrest anchors.