From February, the common EPIRB 121.5 megahertz safety beacon will become obsolete.

When this happens, boats that do not have an updated version will not be able to call for help from search and rescue authorities if they run into trouble at sea.

Jim Orrell, who is the Lake Macquarie Yacht Club's representative on the Yachting NSW special regulations committee, said yesterday people who had not switched to the 406 MHz frequency beacon could find themselves in trouble.

"If you're out off Stockton Bight and you're going under, then your EPIRB is not going to work," Mr Orrell said.

He said the need to switch had been advertised on the internet and in boating magazines but many recreational boat users might not know of the urgent need to update their safety beacon.

"It hasn't had a great amount of exposure," Mr Orrell said.

Authorities in the United States had pushed for the universal introduction of the 406 MHz beacon, because it could provide more accurate data about vessels in distress.

However, the Australian Maritime Safety Authority has estimated there are about 150,000 121.5 MHz distress beacons in Australia that need to be switched before February.

The top-range model 406 beacon costs about $1000.