What are the safety concerns when working on or near "hot" AM towers?
When installing and maintaining wireless equipment on "hot" AM towers, significant safety and operational issues must be carefully addressed. Fortunately, these RF issues are fixable and not a big deal. However, a high level of expertise is required during the planning phase to ensure that all safety and operational issues are addressed.
It is not necessary to turn off the AM radio to install and maintain collocated antenna equipment. Both the FCC and OSHA allow work on "hot" AM towers with appropriate power levels and precautions. FCC "hot" tower guidance can be found in publication OET-65.
FCC/EPA study
FCC OET-65 Guidelines for "Hot" Tower Power Allowed by Climbers
As shown, it is considered safe to climb a heat tower at a certain power level. OET-65 also includes charts that allow determination of safe distances from "hot" towers to stay within maximum allowable exposure (MPE) limits. These determinations vary for each station and are best evaluated by an RF engineer. To recap, for a typical quarter-wave tower, 1000 watts has a safe distance of about one meter, or 10,000 watts has a safe distance of 2 meters.
Many AM stations use more than one tower. Therefore, it should be taken into account that AM stations may operate with different antenna combinations and/or different powers during the day and night. Configuration towers are often chosen to be low power or unused during the day to facilitate base station maintenance.
Since an additive manufacturing station can instantly go from safe mode to dangerous mode without warning, coordinating construction and maintenance activities with the station should be part of project planning. LBA's AM hosting solutions are designed to facilitate "hot" maintenance and prevent unsafe conditions.
Another RF safety tip: Hoisting AM towers can pose a safety risk to personnel hoisting cables and handling any conductive objects overhead on the tower and ground. This is a consideration under the OSHA crane standard, and this blog on RF damage to assemblies will give you a shocking example of why RF cannot be ignored.
The hazards surrounding AM RF are discussed extensively in the LBA paper "Is This Cell Tower Detuned?" Read it to get ready to work in any additive manufacturing facility.
Sometimes it is difficult for someone who is not an AM engineer or a trained AM technician to determine if a tower is a "hot" AM tower, or if the tower is only close to an AM station and detuned. If the station is unable to help locally, LBA staff will be happy to call you at 252-757-0279. We may request photos to help assess the status of the tower. This service is provided free of charge with no obligation.
