The FCC has issued a Notice of Apparent Liability for Forfeiture to four stations with antennas near the Post Office on Mount Wilson that "apparently willfully and repeatedly violated Section 1.1310 of the Commission's Rules by failing to comply with radio frequency radiation (RFR) maximum permissible exposure limits applicable to facilities, operations, or transmitters." FM radio stations KBIG-FM, KKBT and KRTH-FM as well as TV station KWHY-TV were cited.
FCC Rules make any station contributing more than 5 percent of the maximum permissible exposure (MPE) limit for public exposure responsible for ensuring the total RFR level at the site does not exceed the MPE limit. In this case, FCC engineers visiting Mount Wilson found KBIG-FM contributed 81.75 percent of the MPE, KKBT contributed 11 percent, KRTH-FM contributed 11.75 percent and KWHY-TV contributed 10.5 percent. The area around the Post Office at Mount Wilson, where these stations are located, is extremely congested. KBIG-FM is located on a very short tower and the other three stations have antennas at lower elevations than other towers around the site. The extent of RF congestion at the site is evident when comparing the sum of the exposures of these four stations -- 115% of the MPE, with the levels 160.5 percent of the MPE the FCC measured. Using the FCC's methodology, the other 17 stations in the vicinity were contributing 45.5 percent of the MPE, but since their individual contributions were found to be under 5 percent, they were not liable for the excessive RFR.
There are signs warning of RF exposure at the site and under the Notice of Proposed Rule Making on Proposed Changes in the Commission's Rules Regarding Human Exposure to Radiofrequency Electromagnetic Fields, signs warning the public should have been sufficient. However, even though there are numerous warning signs around the location, during the inspection the FCC found they could approach the location with RFR limits above the MPE limit without encountering any of these signs.
The lesson for other broadcast stations at antenna farms is clear. You can be held responsible for RFR in areas outside those you control if your station contributes more than 5 percent of the MPE limit. While it may not be possible for stations to duplicate the results the FCC might find during measurements (RF fields in a complex environment can vary considerably depending on local conditions), having measurements or computer analysis showing your station contributes less than 5 percent of the MPE limit is important. It also shows how one station that is very close to the MPE limits on RFR can drag other stations into possible non-compliance.
In addition to the Notice of Apparent Liability for Forfeiture FCC 03-132, the action is summarized in a New Release FCC Proposes to Fine Four Licensees Total of $40,000 for Jointly Violating RF Radiation Limits.
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