Marine VHF Radio Usage in New Zealand

Click HERE to view the Maritime New Zealand Radio Handbook for Coastal Vessels

Do’s and Don’ts in operating Marine Radios

In the Operation of your Maritime Radio Apparatus

• Use VHF Channel 16 for distress, safety and calling, or the SSB frequency appropriate for your location. Cellphones: call 111.
• Replace your handset correctly when not in use. (Open microphones are the prime cause of serious interference on VHF channels.)
• Listen before transmitting to avoid interference to others.
• Use the vessel’s name and radio callsign.
• Use accepted operating procedures.
• Be brief.
• Speak as clearly as you can.
• Be courteous.
• Wait for a reply to calls before transmitting again, or before changing channels or frequencies.
• Don’t make long transmissions. Remember that many VHF stations are solar powered.
• Don’t transmit false or misleading messages. The transmission of a false distress message is an offence.
• Don’t operate your maritime radio in a manner which endangers or interferes with others
   

HOW RADIO WORKS

Radio waves

Radio transmitters work by supplying a rapidly changing electrical current to an aerial (antenna) to create a changing electromagnetic field. The speed with which these currents change controls the speed that the electromagnetic field around the aerial changes. This is measured in Hertz (Hz).

1Hz    1 Hertz 1 cycle per second
1kHz  1 kiloHertz 1 thousand cycles per second
1MHz  1 Megahertz 1 million cycles per second
1GHz  1 Gigahertz 1 billion cycles per second

Like dropping a pebble into a pond, the pebble represents the transmitter while the radiating ripples represent the fluctuating electromagnetic fields. These radiating electromagnetic fields are called radio waves. These radio waves radiate out from the aerial at the speed of light. Marine VHF operates at a frequency of approximately 156MHz. MF/HF (also called SSB) radios operate at frequencies from about 2MHz to 22MHz.

Frequency characteristics

The different frequencies have different characteristics for specific purposes and are sub-divided into different “bands”. These bands are listed below.

Frequency range Band classification Band abbreviation
 

VHF radio waves travel in a straight line and won’t bend over hills, headlands or over the horizon to any great extent. VHF radio is used for local transmissions but aerials must be in sight of each other (line of sight).

MF radio waves have a greater tendency to follow the earth’s curvature, so lend themselves to medium-range navigation aids, regional broadcasting and for medium-range communications because they can curve around obstructions and over the horizon.

HF radio waves do not bend over the horizon, but utilise a layer of the earth’s atmosphere known as the “ionosphere” to reflect the radio waves back to earth. The ionosphere varies throughout the day but is most stable shortly after sunset. This is a particularly good time for SSB communications in the HF band.

During the daytime, SSB transmissions are not as reliable due to the effect of the sun on the ionosphere. In general, higher frequencies such as 12MHz or 16MHz bands achieve better communications while lower frequencies such as 4MHz or 6MHz work better at night.

The distance between stations is also a factor, with higher frequencies such as 8MHz and above providing better results at longer ranges.

Simplex and Duplex – VHF radio

Simplex means both stations use the same frequency for transmitting and receiving. Duplex is where there is a third station, a repeater station, normally on a high mountain or similar. It receives the incoming signal and simultaneously retransmits it on a different frequency. So duplex uses two frequencies, one to transmit and another to receive.

RADIO TELEPHONE PROCEDURE

The use of radio communications has introduced words and abbreviations and it is important that all radio operators use the correct procedure in the appropriate context.

Turn the radio on and select a channel.

• LISTEN. Others may be using the channel for messages more urgent than your own.
• THINK. Prepare what you are going to say before you transmit, be succinct.
• When not transmitting, be careful not to hold the transmit button down at all times. If this button is jammed or held down by mistake, it prevents any other person from transmitting any messages.
• Safety or lives may depend on clarity in communication.
• Speak simply and enunciate words slowly and clearly using correct procedures and avoid casual technique.

The correct voice procedure is:

PURPOSE OF NEW ZEALAND VHF CHANNELS
 

Phonetic Alphabet

When it is necessary to spell out callsigns/IDs or words, the following spelling should be used: