Tuesday, August 23, 2011

QRM Detectives at Work

Three separate reports are in the news this month of hams helping to track down and resolve interference on the HF amateur bands. The first involved "swishing" sounds heard on the 60-meter (5 MHz) band, first assumed to be signals from the primary users of the band (hams have a secondary allocation there and must accept interference from primary users). However, a joint effort by ARRL Official Observers and researchers at Rutgers University in New Jersey determined that the signals actually were coming from Coastal Ocean Dynamics Applications Radar (CODAR) systems and did not belong on 60 meters. CODAR is an HF radar system used by researchers to study ocean waves and currents. According to the ARRL Letter, the effort led to a frequency change by CODAR, ending the QRM on 60 meters.

In a follow-up action on the west coast, what appeared to be CODAR activity that was causing interference on the 12-meter band was tracked down and the local ARRL OO Coordinator helped resolve the issue.

Finally, Newsline reports that hams around the world worked together in a global hidden transmitter hunt to triangulate the location of the source of a stream of Morse code dits that was heard worldwide for more than a week. It seems that a station in northern California (whose name and call have not been released) accidentally pushed a keyboard against his keyer and unknowingly activated it. The signals stopped immediately after he was contacted by the ARRL.