No matter what amateur radio activities you engage in, I hope that you will engage in them safely. Every year, we lose amateur radio operators because of injuries they sustained while putting up antennas or doing things that could be dangerous. We don’t want to lose you.
Perhaps the most common danger is from lightning strikes. To protect your station, use an external earth connection or ground rod.
What is the primary function of an external earth connection or ground rod? (E0A01)
ANSWER: Lightning protection
RF exposure is another hazard. One of the ways that RF exposure can be hazardous is by causing human tissue to heat up. The amount of heating is proportional to the specific absorption rate (SAR), which is the rate at which RF energy is absorbed by the body.
What does SAR measure? (E0A08)
ANSWER: The rate at which RF energy is absorbed by the body
In order to prevent injuries from RF exposure, the FCC has set maximum permissible exposure (MPE) limits. An MPE limit is the level at which harmful biological effects can occur. Several organizations, including the National Council on Radiation Protection and Measurements (NCRP) and the Institute of Electrical and Electronics Engineers (IEEE) have provided the data used by the FCC to set MPEs. RF exposure limits are most restrictive between 30 and 300 MHz because the human body absorbs radiation at those frequencies more than others.
Over what range of frequencies are the FCC human body RF exposure limits most restrictive? (E0A03)
ANSWER: 30 to 300 MHz
Amateurs operating the microwave bands must also be careful. After all, think about how a microwave oven works. High-power UHF or microwave radiation can also heat up body tissue. Excessive RF exposure can also result from using high-gain antennas when operating the microwave bands.
Which of the following injuries can result from using high-power UHF or microwave transmitters? (E0A11)
ANSWER: Localized heating of the body from RF exposure in excess of the MPE limits
What is one of the potential hazards of operating in the amateur radio microwave bands? (E0A05)
ANSWER: The high gain antennas commonly used can result in high exposure levels
MPE limits for the electric field and magnetic field of an electromagnetic wave differ. There are several reasons for this. First, the body reacts to electromagnetic radiation from both the E and H fields. Second, ground reflections and scattering make the field impedance vary with location. Third, E field and H field radiation intensity peaks can occur at different locations.
Why are there separate electric (E) and magnetic (H) field MPE limits? (E0A06)
ANSWER: All these choices are correct
The body reacts to electromagnetic radiation from both the E and H fields
Ground reflections and scattering make the field strength vary with location
E field and H field radiation intensity peaks can occur at different locations
Remember to include your neighbors when evaluating RF exposure levels. In some cases, your antennas may actually be closer to your neighbors’ houses than they are to your house. That’s why FCC rules require that you must make sure signals from your station are less than the uncontrolled MPE limits when evaluating RF exposure levels from your station at a neighbor’s home.
When evaluating RF exposure levels from your station at a neighbor’s home, what must you do? (E0A02)
ANSWER: Ensure signals from your station are less than the uncontrolled Maximum Permitted Exposure (MPE) limits
Typically, amateur repeater stations are located in places where there are transmitters for other radio services, such as cell phone and pager services. These sites should be regularly evaluated so that RF field strengths don’t exceed the MPE limits. When evaluating a site with multiple transmitters operating at the same time, the operators and licensees of each transmitter that produces 5 percent or more of its MPE exposure limit at accessible locations are responsible for mitigating over-exposure situations.
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? (E0A04)
ANSWER: Each transmitter that produces 5 percent or more of its MPE limit in areas where the total MPE limit is exceeded
Lightning and RF exposure are not the only dangers posed by an amateur radio station. For example, in emergency situations, you may want to use a gasoline-powered generator. One of the dangers posed by a gas-powered generator is that its exhaust contains carbon monoxide. To ensure your safety and those around you, make sure you use a carbon monoxide detector wherever fumes may accumulate.
How may dangerous levels of carbon monoxide from an emergency generator be detected? (E0A07)
ANSWER: Only with a carbon monoxide detector
Some of the materials used in electronics pose a danger to amateur radio operators. They are used because they have some desirable electrical property, but may be dangerous if used improperly. For example, beryllium oxide is an insulating material commonly used as a thermal conductor for some types of electronic devices that is extremely toxic if broken or crushed and the particles are accidentally inhaled. Another toxic material, polychlorinated biphenyls (PCBs), can be found in some electronic components, such as high-voltage capacitors and transformers.
Which insulating material commonly used as a thermal conductor for some types of electronic devices is extremely toxic if broken or crushed and the particles are accidentally inhaled? (E0A09)
ANSWER: Beryllium Oxide
What toxic material may be present in some electronic components such as high voltage capacitors and transformers? (E0A10)
ANSWER: Polychlorinated biphenyls
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