The Case of the RF Disturbances

I was posted at the same station Chris Spacone described in the Sherlock posting The Case of the Stuttering Tape Drive a couple of years after Chris left. The PDSs (program development stations) for several of the ATE (automatic test equipment) stations had been moved back into the room facing the runway and the surveillance radar site. The new solution had been to cover the windows with aluminum foil to block the high-power radar signals. It was crude but effective.

My first computer was a RS color computer, or COCO, as they were called. The programs were stored on a regular audio cassette tape drive. When I set up my computer and tried to load programs from tape, I would get random I/O errors. If it was a long program, I would not be able to load it. I thought all my program tapes had been damaged in shipping.

That went on for a couple frustrating days. One day, I was listening to the stereo while working on the computer at home. The stereo started to emit a periodic buzzing approximately every 12 seconds. I was trying to load a program. Almost simultaneously the stereo went bzzt, and the computer halted loading for an I/O error.

Eureka! My apartment was on the third floor of the building on the side facing the radar site, which was only a couple of miles away. The period of the dish rotation was approximately 12 seconds. Every time the main beam swung past, the electronics in the apartment went crazy. Touch lamps would turn on or off by themselves. The TV cable box would change channels or turn itself on.

To fix my tape drive, I shielded it with aluminum foil. The noise was reduced, but I still had occasional errors. Within a couple of months, my final solution was to move well away from the radar site. I hate to think of what that RF energy was doing to people who stayed in that building.

The radar also affected the fluorescent tubes we used to test emissions. We used a neon bulb. The bulb would light up in the presence of strong RF signals. You could even set off photo flash bulbs with the radar pulse.

This entry was submitted by Brian Jahraus and edited by Rob Spiegel.

Brian Jahraus joined the Canadian Air Force right out of high school, becoming an Airborne Radar Technician. He served 22 years in the military, including 13 years in Cold Lake, Alberta, where he was born. He is now employed as an instrumentation technologist doing wind tunnel instrumentation support. In addition to his military training, Brian also completed a four-year college diploma in telecommunications technology through part-time studies. He has an interest in computers, both hardware and software, as well as an interest in robotics, astronomy, and vintage motorcycles.

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