What is Interference?

In the early years of radio and television broadcasting, with few electronic devices in homes
or businesses, RF interference was only an irritation when trying to receive radio and TV
broadcasts. With the advent of the “electronic age,” RF interference is now considered to be
much more significant. With electronic devices becoming ever more ubiquitous and sensitive,
RF interference has become a major concern, not only to consumers, but to businesses.
 

FCC Interference Limits

The federal limit for human exposure to RF radiation is 200 microwatts per square centimeter or more, depending on frequency. Interference to electronic equipment may occur at much lower levels. The FCC recognizes this, and has set “blanketing interference” standards for AM and FM radio, but not for television. The FCC considers a blanketing interference condition to exist in any area where the antenna is capable of producing a power density greater than .084 microwatts per square centimeter. If the blanketing interference standards were applied to television signals, the blanketing interference zone would extend for a distance of 8 miles from a full power DTV transmitter. When multiple transmitters are located at the same site, the likelihood of interference becomes even greater.

The FCC’s 1934 charter provides for regulations that minimize interference between broadcast stations, but the FCC does not regulate interference caused by its licensees to business or research equipment.

The FCC states that it is the traditional role of local government to determine the placement, construction and modification of broadcast facilities, but once a broadcast facility has been built, the FCC claims exclusive authority over RF interference, and that agreements between local authorities and the FCC’s licensees (such as the interference mitigation agreement between Jefferson County and Lake Cedar Group) are void and unenforceable.

To read the entire FCC Interference Preemption Ruling (DA-03-2196A1), click here...

It is clear from this ruling that local governments must take extreme care when locating high
power broadcast facilities to ensure that these facilities will do no harm to the local economy.
 

Colorado State Legislators Recognize RF Issues

Legislators in the Colorado State Senate also recognize the problems caused by high power broadcast facilities. In a letter to the Jefferson County Commissioners, legislators urged them to deny the proposal stating, "The interference caused by these proposals is counter-productive to the best interests of Jefferson County." To read the Senate letter (hearing record 2704,2705), click here...