By Bob Clarke
In the 70s I was an onsite guarantee engineer deployed for a year. Located at a very isolated spot in northern Norway, NATO had erected a high-power very low-frequency radio transmitter. With several hundred kilowatts and an antenna length over 500 meters, this is specialized stuff. The idea behind it was high penetration, and during the cold war it was reaching unmentionable places.
The control room those days had a large steel desk with a back panel mounted on it. All the controls were analog. Indicating meters had needle movements showing power consumption. To set the output power, there was a single large potentiometer with a fist-sized knob centered on the desktop. Just days after turnover to the local operators, sudden arc-overs started occurring. Due to the size and power of this transmitter, it’s was a really big bang, not unlike a lighting strike.
At first it was thought that a passing cloud had discharged through the antenna. But it was happening too regularly. Talking to the operator on duty didn’t reveal anything unusual. With the normal duty watch rotation, it also happened to different people. Going through the system, I found it was a really big bang discharge at the base of the antenna. But watching it there didn’t give me any clue as to why it occurred. I was getting a bit annoyed because it seemed to happen just after I got home from work. In fact, it was usually between 5 pm and 6 pm, but not every day and never on weekends.
I decided to do some “busy work” and stay in the back corner of the control room at the critical time. First day, nothing happened and there was no big bang. Second day, I moved aside to let the cleaning woman do her job. Then watched in horror as she wiped a cloth over the control desktop and polished the big knob! There was a resulting big bang, and the operator scrambled to get everything back on line again. She just finished up and left the room. The operator didn’t even recall that she’d been there.
The next day we took the control desk off of the cleaning routine and placed a cup shaped protector over the power knob. No more big bangs.
Bob Clarke is a U.S. Navy trained electronic technician. He started out as a ships radar tech in Vietnam. He is currently doing factory automation in Norway.