Boating New Zealand — December 2017

104 Boating New Zealand

A VHF radio is a line-of-sight device, so the effective range is largely

dependent on whether the antenna of the transmitter can ‘see’ the

receiver. Because of the earth’s curvature, this means that the longer

and higher the antenna the greater the distance to the horizon, and

the greater the VHF signal’s range. When standing 1m above the

water, the horizon is 3.6km away.

To double this distance you need to get four times as high, i.e.

at 4m above the water surface the horizon will stretch to 7.1km

away. Of course, Maritime NZ places its radio masts on high points

on islands and headlands, so the effective range when calling the

Coastguard is considerable.

That side of the equations is out of your control, but by getting

your antenna mounted as high as you possibly can you maximise

your part and increase overall capability.

ANTENNA HEIGHT AND EFFECTIVE RANGE?

EARTH

TRANSMIT

ANTENNA

RECEIVE

ANTENNA

SIGNAL PROPAGATION

BELOW Checking the

fold-down option.

RIGHT VHF

communication relies on

line-of-sight between

transmitter and receiver.

FAR RIGHT Mount the

antenna on the highest

point of the boat.

Whether you’re racing up the coast, or around the globe, you

can rely on North Sails cutting edge technologoy to outperform

the competition. To find out more contact us today.

LOCAL

GLOBAL

T 09 359 5999 E [email protected] northsails.com