TC 9-64 _________________________________________________________________________
RF BURNS
4-7. 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
4-8. 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.
4-9. 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.
4-10. 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.
4-11. 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.
PRINCIPLES OF ANTENNA RADIATION
4-12. After an RF signal has been generated in a transmitter, some means
must be used to radiate this signal through space to a receiver. The device
that does this job is the antenna. The transmitter signal energy is sent into
space by a transmitting antenna; the RF signal is then picked up from space
by a receiving antenna.
4-13. The RF energy is transmitted into space in the form of an
electromagnetic field. As the traveling electromagnetic field arrives at the
receiving antenna, a voltage is induced into the antenna (a conductor). The
RF voltages induced into the receiving antenna are then passed into the
receiver and converted back into the transmitted RF information.
4-14. The design of the antenna system is very important in a transmitting
station. The antenna must be able to radiate efficiently so the power supplied
by the transmitter is not wasted. An efficient transmitting antenna must
have exact dimensions. The dimensions are determined by the transmitting
frequencies. The dimensions of the receiving antenna are not critical for
relatively low radio frequencies. However, as the frequency of the signal
4-4
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