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Most studies on the subject of radiation hazards (RADHAZ) have emphasized the impact of
electromagnetic radiation on man. Man is singled out because of the biological, thermal, and neurological
effects that occur in human organs and other biological tissues. Certain organs of the body are considered
to be more susceptible than others to the effects of electromagnetic radiation. Presently available
information and experience indicate that the eyes and testes are the most vulnerable body organs. The
overwhelming danger to date appears to be the hazard from thermal effects, which are a function of
intensity of radiation and frequency. This is particularly true in the range of 1 to 3 gigahertz. Thermal
effects appear to taper off in severity outside this range.
When the body is irradiated by energy from a point source, the total body surface is usually not
exposed. The larger the area exposed and the larger the radiation power density, the higher the body
temperature rise and the greater the hazard. Microwave radiation from a radar source will "cook" you
internally, just as a microwave oven cooks a chicken.
An injury of great concern is that to the lens of the eye. Exposure of the lens to high-intensity
microwaves may cause cataracts. Current medical evidence indicates that a significant temperature
elevation of the lens is required for cataract formation. If exposure is limited to 10 milliwatts per
centimeter squared, the lens temperature is not elevated to levels at which cataracts occur.
In addition to thermal effects, nonionizing radiation is known to produce nonthermal effects. An
association of a biological hazard with the nonthermal effects has not been demonstrated.
A peculiar effect experienced by some personnel is the sensation of sound when they are exposed to
pulsed microwave fields. This occurs at levels below stated hazard limits and is not, by itself, considered
dangerous.
Q38. Electromagnetic radiation is hazardous to personnel in what two ways?
Q39. What is the most useful and widespread technique to reduce rf burn hazards?
SUMMARY
Now that you have completed this chapter, a short review of what you have learned is in order. The
following summary will refresh your memory of basic systems equipment, its principles, terms, and
typical circuitry required for you to understand this concept.
A RADIO SET CONTROL UNIT is used to remotely control certain transmitter and receiver
functions.
TRANSMITTER TRANSFER SWITCHBOARDS selectively transfer remote control station
functions and signals to transmitters.
RECEIVER TRANSFER SWITCHBOARDS transfer receiver audio outputs to remote control
station audio circuits.
A TRANSMITTER generates an rf carrier, modulates it with intelligence, amplifies it, and applies
it to an antenna.
An ANTENNA COUPLER is a device used for impedance matching between an antenna and a
transmitter or receiver.
A RECEIVER receives electromagnetic energy (rf) and may convert it to a visible or audible form.
