There are many unknowns concerning the safe limits of human exposure to
radio frequency (RF) radiation. The use of the word radiation does not
necessarily connote any linkage to nuclear fission or other radioactive
processes, but rather non-ionizing radiation of radio emissions. The general
rule is to not subject living things to radiated RF energy unnecessarily. This
means that one should not stand in front of, or in close proximity to, any
antenna that is radiating a transmitted signal. Antennas that are only used for
receiving do not pose any danger or problem. For dish-type antennas it is safe
to be near an operating transmitting antenna if one stands to the back or sides
of the antenna. These antennas are directional, and potentially hazardous
emission levels will only be present at the front of the antenna.
One
should always assume that any antenna is currently energized, especially since
most antennas are used in duplex systems. Small-sized dishes of 30 cm (1 ft) or
less are often radiating RF energy in the tens-of-gigahertz frequency range. As
a general rule, the higher the frequency, the more potentially hazardous the
radiation. Care should be taken to ensure that the transmitter is not operating
before removing or replacing any antenna connections.
It is important
not to stand in front of, or walk around, microwave antennas that are being
installed on rooftops. If it is necessary to walk in front of any such
antennas, there is typically a very low safety concern if one moves briskly
across the path axis of the antenna. In order to comply with RF exposure limits
established in the ANSI C95.1 standards, it is recommended that when using a
laptop with a PC card client adapter, the integrated antenna of the adapter
should be positioned more than 5 cm (2 in.) from the body of the operator or
other nearby persons. This is especially true during extended periods of
transmitting or operating time. It is recommended to limit exposure time if the
antenna is positioned less than 5 cm (2 in.) from the user. Remember that the
computer may be carrying on background network communications, even if the
network is not actively being used.