E-10

E-10

Read Cliff Notes

E0A Safety: amateur radio safety practices; RF radiation hazards; hazardous materials; grounding

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 mitigate the danger of a lightning strike, you should use properly grounded lighting arrestors. The primary function of an external earth connection or ground rod is lightning protection. (E0A01)

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). SAR measures the rate at which RF energy is absorbed by the body. (E0A08)

In general, the SAR increases as the frequency increases. Think microwave ovens. They heat food because water in the food absorbs microwave radiation. The maximum permissible exposure (MPE) 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.

Localized heating of the body from RF exposure in excess of the MPE limits is an injury that can result from using high-power UHF or microwave transmitters. (E0A11) One of the potential hazards of using microwaves in the amateur radio bands is that the high gain antennas commonly used can result in high exposure levels. (E0A05)

The FCC, as you might expect, has a lot to say about RF exposure. They have set limits on the field strengths that humans may be exposed to. These limits are called maximum permissible exposure, or MPE.

The MPEs for the electric field and magnetic field of an electromagnetic wave differ. All of these choices are correct as to why there are separate electric (E) and magnetic (H) field MPE limits (E0A06):

  • The body reacts to electromagnetic radiation from both the E and H fields
  • Ground reflections and scattering make the field impedance vary with location
  • E field and H field radiation intensity peaks can occur at different locations

 

To make sure that your transmissions do not expose you or others to field strengths above the MPE limits. You could measure the absolute field strengths. Unfortunately, this is not easy to do. The equipment used to measure field strength is very expensive and difficult to use. An alternative is to use software that calculates field strength. Using an antenna modeling program to calculate field strength at accessible locations would be a practical way to estimate whether the RF fields produced by an amateur radio station are within permissible MPE limits. (E0A03)

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. When evaluating RF exposure levels from your station at a neighbor’s home, you must make sure signals from your station are less than the uncontrolled MPE limits. (E0A02)

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. (E0A04)

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. Dangerous levels of carbon monoxide from an emergency generator can be detected only with a carbon monoxide detector. (E0A07)

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. (E0A09) Polychlorinated biphenyls, or PCBs, is a material found in some electronic components, such as high-voltage capacitors and transformers, that is considered toxic. (E0A10)

Watch PowerPoint

[embeddoc url=”http://www.w4catest.org/wp-content/uploads/2018/05/11-E0.ppsx” download=”all” viewer=”microsoft”]

Go to ARRL Exam Review

Sign IN

Review for Exam

General Review

Review by Subelement

Select Groups from Individual Subelements

Select ALL

Check % on the Right Side

LOOKING for 85% or BETTER

Use the Left Arrow Key

ARRL Exam Review

You Are Done!!! Go to QRZ.com & Start Testing.