Blockers break ban

Sellers or users of jamming devices are liable to a fine of up to $1250. Photo / Supplied

Devices that block mobile phone and GPS signals are being sold illegally on New Zealand internet sites.

The jamming devices, which have sold for as little as $99 on Trade Me and Sella, may not be used in this country without a licence, and selling or manufacturing them is banned.

Some versions can interfere with aircraft navigation and police communications, and US experts claim they can bring down a plane.

Only the Corrections Department may use mobile phone jammers and only within prisons.

The Ministry of Economic Development said the devices could stop people making emergency calls. Compliance manager Chris Brennan said about one a week was removed from sale on the internet. Sellers or users are liable to a fine of up to $1250.

Last year an Auckland church was fined for using a jamming device to block mobile phone use during services.

"We'd be concerned if we found anybody offering something that intentionally interfered with communications for safety services," Brennan said.

One GPS jammer sold on Trade Me was advertised with a listing: "Never be tracked again! Great for using the company vehicle on weekends and for being where your [sic] not meant to be!"

A listing on auction website Sella offered several devices, including a "covert portable GPS jammer" and a broad-spectrum cellphone jammer, priced at $99. A more sophisticated device with a bigger range was listed at $399.

Sella business manager Casey Eden said jammers were removed as soon as they were found, and details were forwarded to the ministry.

"We monitor [it] very closely, but when someone puts it under kids' toys, it's hard to catch it."

Trade Me trust and safety manager Chris Budge said at least five jamming devices had been listed in the past year. Three auctions were removed, but two slipped through checks and were sold. There had been more than 600 searches for various types of jammers in the past 30 days.

Maritime New Zealand's Jim Lott said jammers could interfere with GPS systems, but vessels generally used more than one means of navigation, because electronic devices could fail.

Civil Aviation Authority spokesman Bill Sommer said it was possible for a jammer to compromise aircraft navigation, but there had been no known instance in New Zealand of that happening.

heather.mccracken@hos.co.nz