Winter 2006 Issue


Spurious Signals and Offset Attenuators

By Joe Moell, KØOV

“A mysterious man in a red pickup truck is driving around and pointing a suspicious device from the window!” That’s what a caller told the sheriff’s dispatcher in Washington, Iowa last August. Fortunately, there was no overreaction from authorities in this town of 7050 souls about 45 miles south of Cedar Rapids.

As the Washington Evening Journal reported, it was just the first in a series of ham radio “foxhunts.” From the article: “Tally Ho? Four teams of members from the Washington Amateur Radio Club, with visitors from the Ottumwa club tagging along, all started at different points in the city and then used home-made direction-finding antennas and hand-held radios to converge on the ‘fox,’ which had been hidden earlier in West Haven Cemetery.”

This publicity was excellent, as was an August article about Scott Fenstermacher, AG4GO, in The Daily Press of Hampton Roads, Virginia under the headline “Amateur Radio Expert Loves Thrill of the ‘Fox Hunt.’” The subheading was “Gloucester man has turned a simple hobby into one that entertains, teaches, and even saves lives.” It told how he and his son Phillip, KG4GYT, “serve on the local SKYWARN team and practice radio direction finding (RDF) skills that could find downed aircraft or missing emergency vehicles.”

As I have written many times before, the time to learn RDF proficiency is before you need it. Regular practice paid off for hams in the South Orange Amateur Radio Association (SOARA) of Orange County, California in December, as I heard from Richard Saunders, K6RBS. “I keep every southern California 2-meter open repeater in the memories of my FT-857,” he told me. “I regularly scan through and listen to what’s going on.

“A few weeks ago, I began hearing a strange noise on one of the repeaters,” K6RBS continued. “Then I started to hear it on two or three of the repeaters. That got me interested, because one repeater can have a technical glitch, but it would be very unusual for several to have the same problem. I went to VFO mode and tuned around. The noisy signal was moving around on the top end of the band. It was difficult to describe, but sounded sort of like AC hum or video buzz. It would sit on one repeater frequency for a while and then move on to another one.”

Dave Seroski, KG6QCI, enjoys being hider and promoter of SOARA mobile T-hunts. He helped Richard Saunders, K6RBS, track down a spurious 2-meter signal in Lake Forest, CA. (All photos by Joe Moell, KØOV)

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