RF Safety

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As the FCC becomes more environmentally minded, RF safety takes on a greater importance. Radiation seems to be a taboo word in America. We tend to give any mention of radiation a wide berth. While it is true that radiation can be harmful, it is important to remember that the stuff we are talking about in radio is not the same as that from power plants or bombs.

Radio radiation is non-ionizing. This means that when it strikes or passes through a material it has insufficient energy to ionize atoms. Rather, we see that radio waves typically cause changes in the vibrational and rotational configurations. In other words, radio frequency energy tends to heat a medium. Intuitively this should make sense, as this is the concept behind a microwave oven.

An example of improper sign placement.

An example of improper sign placement.

Our goal, then, is to reduce the potential for a similar effect in body tissues. To that end, standards have been developed over the years to describe and provide guidance toward minimizing the potentially harmful effects on humans. The latest revision of the venerable IEEE C95.1 standard is the 2005 revision, although the Commission still utilizes portions of the 1992 revision. The IEEE standard is not necessarily ubiquitous on a global scale, as other countries may utilize their own standards. Some of these are tighter than the IEEE standard, and some go the other way.

Other portions of the FCC's adopted procedures, including the exposure limits, are based on recommendations from the National Council on Radiation Protection and Measurements (NCRP). These requirements, available from the Office of Engineering and Technology section of the FCC home page, are the result of the National Environmental Policy Act of 1969. While some of the other portions of this legislation may be of dubious importance, the protection of personnel and the public from the generally undetectable hazards of RF radiation makes sense.

Make a plan

To promote awareness of RF hazards and mitigate their effects at your facility it is necessary to implement an RF safety plan. Under such a plan you are definitively recognizing and defining the potential harmful effects, establishing procedures that employees and contractors must follow, and identifying physical areas that may be problematic for exposure. While a boiler-plate approach is a good first iteration for a facility, it is crucial to recognize that each facility is unique, and therefore will likely require a customized solution. These suggestions are not meant to be an exhaustive list, and it is recommended that you consult with a competent engineer when you build your plan.

Typically hazards can be split into two general categories: contact hazards and non-contact hazards. Contact hazards are situations, as the name suggests, where the human body comes into direct physical contact with the hazard. The archetypal example here is coming into contact with a hot AM tower. Exposure to physical contact hazards can be minimized through a combination of barriers, reduction in transmitter power and cessation of operation. The general result of a contact hazard is the RF burn (a.k.a. the rite of passage).

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