The Northland Coastguard Air Patrol flew from Kerikeri to Rāwene on Friday via a very circuitous route, on a very unusual mission.

"We were asked by Radio Spectrum Management, the agency that administers New Zealand radio frequencies, to identify the source of a 'white noise' transmission that was continuing to block some usage of the VHF Channel 16 distress channel," vice-president Peter Heath said.

"It's quite a big deal if people can't call for help on the radio, so it was potentially a very serious situation."

The search began at 9am, using the aircraft's radio direction finding kit, technology dating all the way back to WWII, to locate the source of the problem.


"It didn't take too long for pilots Andrew Roberts and Larry Sutherland, aided by observer Ted Kirkbride, with observers Jan Kennedy and Tim Hamer crewing the Ops Room to maintain contact with the aircraft and relay messages, to figure out that it was coming from somewhere on the west coast. From there it was just a matter of narrowing down the search until we had a likely location.

"Lo and behold, it was tracked down to somewhere within Rāwene township. We couldn't fly low enough to absolutely pinpoint the source, so the plane returned to base, leaving Radio Spectrum to finish the job."

Mr Heath declined to speculate on what had given rise to the problem, beyond saying he suspected it was inadvertent as opposed to sinister.

"Radio Spectrum Management was delighted, because now their land-based teams could focus in on a very specific area, whereas before it would have been like looking for a needle in a haystack," he added.

"If you are anywhere in the Rāwene area and you know of a piece of equipment that might be unattended and broadcasting away on Channel 16, please switch it off!"

Radio Spectrum Management was unable to confirm by yesterday's deadline whether the problem had been resolved.