Extra exam: safety
RF exposure, hazardous materials and safe station practice. 12 questions, 10 at a time, starting with ones you haven't seen.
Rules to remember7 key safety rulesShow the rules
- An external ground rod gives lightning charge a low-impedance path into the earth, so it dissipates outside the house instead of through your equipment. (p. 116)
- A neighbor is a member of the general public who doesn't know about your transmissions, so the stricter uncontrolled (general population) exposure limits apply there. (p. 116)
- Microwave stations often use very high-gain dish or array antennas, which concentrate power into a narrow beam and can create high exposure levels near it. (p. 117)
- 100% tie-off means the climber is always connected to the tower by at least one lanyard, even while moving a lanyard to a new spot. (p. 117)
- SAR, the specific absorption rate, measures how fast the body absorbs RF energy, in watts per kilogram of tissue. (p. 117)
- Under the FCC's 2021 RF exposure rules, hand-held transceivers sold before May 3, 2021 are exempt from a new routine evaluation. (p. 117)
- Lanyards should be attached to the tower legs, the main structural members strong enough to arrest a fall. (p. 118)
Taken from the explanations to checked practice questions; page numbers link to the official handbook.
Sample safety questions
1.Over what range of frequencies are the FCC human body RF exposure limits most restrictive?
- A30 - 300 MHz
- B3 - 30 MHz
- C300 kHz - 3 MHz
- D300 - 3000 MHz
Show the answer
✓ A. 30 - 300 MHz
The human body absorbs RF most efficiently around its resonant frequencies, which fall in the 30-300 MHz range, so the FCC exposure limits are lowest there.
2.What is meant by "100% tie-off" regarding tower safety?
- AAt least one lanyard attached to the tower at all times
- BAll loose ropes and guys secured to a fixed structure
- CAll tools secured to the climber's harness
- DAll circuit breakers feeding power to the tower must be tied closed with tape, cable, or ties
Show the answer
✓ A. At least one lanyard attached to the tower at all times
100% tie-off means the climber is always connected to the tower by at least one lanyard, even while moving a lanyard to a new spot.
3.What does SAR measure?
- AThe rate at which RF energy is absorbed by the body
- BSignal attenuation ratio
- CThe rate of RF energy reflected from stationary terrain
- DSignal amplification rating
Show the answer
✓ A. The rate at which RF energy is absorbed by the body
SAR, the specific absorption rate, measures how fast the body absorbs RF energy, in watts per kilogram of tissue.
4.What hazard is created by operating at microwave frequencies?
- AThe high gain antennas commonly used can result in high exposure levels
- BMicrowaves are in the frequency range where wave velocity is higher
- CMicrowaves are ionizing radiation
- DThe extremely high frequency energy can damage the joints of antenna structures
Show the answer
✓ A. The high gain antennas commonly used can result in high exposure levels
Microwave stations often use very high-gain dish or array antennas, which concentrate power into a narrow beam and can create high exposure levels near it.