Consulting Engineer
Electrical & Electronics
Home Cases Contact

Harmful Radio Interference

A rural facility provided radios for on-site use by its own employees and by outside construction personnel. Two radio channels were available: a main channel for facility employees and an auxiliary channel for construction workers. It was well known that intermittent interference occurred on the auxiliary channel, during which ordinary telephone conversations were clearly heard.

A construction foreman and a crane operator, out of sight of each other, were communicating on the auxiliary channel. The crane operator claimed that interference obscured a command to stop lifting an object which had caught on something. The lift cable then parted and its falling lower end hit the foreman, causing a disabling hand injury. The foreman filed a personal injury lawsuit against several parties, including the facility's owner.

The auxiliary-channel interference was most likely caused by same-channel transmissions of a private or community repeater interconnected to a telephone company. Users of this type of repeater could access the telephone system through handheld radios (but not cell phones) similar to those used at the facility.

The repeater and the facility's radios operated in a particular band of frequencies with a large number of users and frequent interference. However, the facility was eligible to operate in a different band, restricted to a small number of similar-industry users and providing dependable communications with little interference.

It's unknown why the facility hadn't taken advantage of the restricted band. When faced with a set of interrogatories addressing that and other steps that could have been taken to mitigate the interference problem, the facility's owner chose to seek a settlement.

Phone: 818.903.7030
© 2010 H. Clark Bell, all rights reserved.