[RFI] RFI source found!
Brian Davis
bdavis73 at comcast.net
Sat Aug 27 12:15:28 EDT 2016
I am relaying the event of my ham friend, Ken, W9IE, who has been plagued with serious RFI spurs on all bands 20 meters and above. It bothered him for several years. It made some frequencies on two meters unusable including 146.94 FM. It varied in frequency in that it slowly drifted across the FM repeater channel. Using a portable receiver it was determined to be outside his house (he did pull all the breakers in his house). Next suspect was the Comcast distribution amplifier high on a pole outside his house. For some reason he followed the cable drops radiating from the pole in each direction using his radio to track the noise. One path took him to the next door neighbor where the noise got quite loud. Ah ha…he says. The neighbor was very cooperative and they systematically opened breakers in the power panel. When they got to the family room the noise in the portable radio stopped. Trouble was, there was little in the family room except reading lights. On a hunch Ken asked what was on the other side of the wall. It turned out to be the garage powered by the same circuit. A quick survey reveled a Hitachi 7.2 to 14 volt Ni-Cad/Ni-MH (model UC-14VFA) cordless drill battery charger that was plugged in all the time. Testing showed RFI anytime the charger was plugged in, battery or not caused serious RFI. Ken took his neighbor to a local big box store and bought the him a new Dewalt cordless drill system. Ken joked he was glad that the noise did not come from a washing machine or flat screen TV. Neighbor rewarded for being cooperative and the was problem solved! 73, Brian W9HLQ
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