4-47
sheets. The construction of a corner reflector is shown in figure 4-42. Corner-reflector antennas are
mounted with the radiator and the reflector in the horizontal position when horizontal polarization is
desired. In such cases the radiation pattern is very narrow in the vertical plane, with maximum signal
being radiated in line with the bisector of the corner angle. The directivity in the horizontal plane is
approximately the same as for any half-wave radiator having a single-rod type reflector behind it. If the
antenna is mounted with the radiator and the corner reflector in the vertical position, as shown in view A,
maximum radiation is produced in a very narrow horizontal beam. Radiation in a vertical plane will be the
same as for a similar radiator with a single-rod type reflector behind it.
Figure 4-42.—Corner-reflector antennas.
Q48. What is the primary reason for the development of the turnstile antenna?
RF SAFETY PRECAUTIONS
Although electromagnetic radiation from transmission lines and antennas is usually of insufficient
strength to electrocute personnel, it can lead to other accidents and compound injuries. Voltages may be
induced in ungrounded metal objects, such as wire guys, wire cable (hawser), hand rails, or ladders. If you
come in contact with these objects, you could receive a shock or rf burn. This shock can cause you to
jump or fall into nearby mechanical equipment or, when working aloft, to fall from an elevated work area.
Take care to ensure that all transmission lines or antennas are deenergized before working near or on
them.
Either check or have someone check all guys, cables, rails, and ladders around your work area for rf
shock dangers. Use working aloft "chits" and safety harnesses for your own safety. Signing a "working
aloft chit" signifies that all equipment is in a nonradiating status. The person who signs the chit should
ensure that no rf danger exists in areas where you or other personnel will be working.
Nearby ships or parked aircraft are another source of rf energy that you must consider when you
check a work area for safety. Combustible materials can be ignited and cause severe fires from arcs or
heat generated by rf energy. Also, rf radiation can detonate ordnance devices by inducing currents in the
internal wiring of the devices or in the external test equipment or leads connected to them.
ALWAYS obey rf radiation warning signs and keep a safe distance from radiating antennas. The six
types of warning signs for rf radiation hazards are shown in figure 4-43.
