In 1989 a SCADA sytem was being prepared for an oil company in Houston Texas. All the remote telemetry units were communicating with the master station computer via low power Johnson radios. The dummy loads on all of the antennae were used to cut down the range of the transmissions, (this caused havoc with the SWR’s and other equipment but the transceivers could be adjusted to get decent communications most of the time). Sporadically there would be bursts of errors for seemingly no reason. Using data analysers, junk could be seen on the frequency but could not be identified.

Using a telephone handset on a circuit to listen to the ‘noise’  it was established that a delivery truck was talking to his dispatcher at the same time that the communications efficiency dropped to zero. (#1)

Unknown.