PRECAUTIONS WHEN WORKING ALOFT

4-49 RF BURNS Close or direct contact with rf transmission lines or antennas may result in rf burns. These are usually deep, penetrating, third-degree burns. To heal properly, these burns must heal from the inside to the skin's surface. To prevent infection, you must give proper attention to all rf burns, including the small "pinhole" burns. Petrolatum gauze can be used to cover these burns temporarily, before the injured person reports to medical facilities for further treatment. DIELECTRIC HEATING DIELECTRIC HEATING is the heating of an insulating material by placing it in a high-frequency electric field. The heat results from internal losses during the rapid reversal of polarization of molecules in the dielectric material. In the case of a human in an rf field, the body acts as a dielectric. If the power in the rf field exceeds 10 milliwatts per centimeter, a person in that field will have a noticeable rise in body temperature. The eyes are highly susceptible to dielectric heating. For this reason, you should not look directly into devices radiating rf energy. The vital organs of the body also are susceptible to dielectric heating. For your own safety, you must NOT stand directly in the path of rf radiating devices. PRECAUTIONS WHEN WORKING ALOFT When radio or radar antennas are energized by transmitters, you must not go aloft unless advance tests show that little or no danger exists. A casualty can occur from even a small spark drawn from a charged piece of metal or rigging. Although the spark itself may be harmless, the "surprise" may cause you to let go of the antenna involuntarily and you may fall. There is also a shock hazard if nearby antennas are energized. Rotating antennas also might cause you to fall when you are working aloft. Motor safety switches controlling the motion of rotating antennas must be tagged and locked open before you go aloft near such antennas. When working near a stack, you should draw and wear the recommended oxygen breathing apparatus. Among other toxic substances, stack gas contains carbon monoxide. Carbon monoxide is too unstable to build up to a high concentration in the open, but prolonged exposure to even small quantities is dangerous. SUMMARY This chapter has presented information on the various types of antennas. The information that follows summarizes the important points of this chapter. An ANTENNA is a conductor, or system of conductors, that radiates or receives energy in the form of electromagnetic waves. HERTZ (half-wave) and MARCONI (quarter-wave) are the two basic classifications of antennas. RECIPROCITY of antennas means that the various properties of the antenna apply equally to transmitting and receiving.