Making a connection through the radio mess

Like Australia's government - federal, state and local - the marine radio system is now a three-tier business.

The upper-tier, official Maritime Communication Stations (MCS) are located at Wiluna in WA and Charleville in Queensland, from where they issue weather forecasts and warnings, monitor HF (High Frequency) digital selective calling (DSC) frequencies for distress calls and initiate search and rescue (SAR) operations in conjunction with the Rescue Coordination Centre (RCC) in Canberra.

The next tier down is state and territory-operated Coast Radio Stations (CRS), located in all the capital cities (except Brisbane) and in Cairns, Gladstone and Port Hedland. These stations are licensed as HF stations and maintain a 24-hour listening watch on channels 4125, 6215 and 8291kHz for distress calls and broadcast navigation warnings on 8176kHz.

CRS services include some VHF coverage, on channels 16 and 67.

The third tier consists of specialised and volunteer-manned Limited Coast Stations (LCS). Only some of these stations offer 24-hour monitoring of distress channels in the MF/HF, VHF and 27mHz bands. It's notable that only LCS installations monitor the 27mHz frequency.

To contact the three-tier radio station network it's necessary to have three different radios onboard your boat and, in the case of contact with MCS locations, the HF unit has to be a DSC-equipped radio.

WHAT DO YOU NEED?
It may seem like teaching your grandmother to suck eggs, but it's surprising how few boaties know the difference between different radio types.

The radio energy that leaves antennae can be broadly split into waves that travel close to the surface of the earth (ground waves) and those that travel into the heavens (sky waves). The ground wave loses energy quickly and is therefore reliable only over relatively short distances. The sky wave travels as far as the ionosphere and then 'bounces' back to earth, making it more suitable for long-distance communication.

MF/HF radios are designed to exploit sky-wave reflection and are the ones intended for long-distance communications. MF/HF radios also have a wide frequency choice, most commonly between the 2mHz and 16mHz bands, allowing operators to choose frequencies that suit different distances and atmospheric conditions.

It's possible to have sky-wave signal enhancement of 27mHz signals, under certain atmospheric conditions, and there are many recorded instances of 'skip' communications across Australia on 27mHz radios, but the phenomenon is wildly variable and cannot be relied upon.

VHF radios normally don't enjoy ionospheric signal reflection and are intended for short-distance communications.

So, for enclosed waters and near-coastal cruising, where short-distance communication is required, a 27mHz and/or a VHF radio are the most likely requirements. For longer voyages and extended coastal cruising an MF/HF set is necessary.

27mHz
'Twenty-seven-meg marine' is the boaties' equivalent of land-based 27mHz CB radio. Sets are generally cheap - less than $200 - and provide a ground-wave range of between five and 25nm. Handheld models are available.

The 27mHz band is normally limited to line-of-sight communications and can be affected by atmospheric and electrical conditions, and by other radio noise.

VHF
VHF radios are two to three times the price of 27mHz radios, but offer higher wattage and much better signal quality, which can increase range to shore stations well beyond the 25 miles or so provided by 27mHz radios.

Handheld models are available, but they're generally more expensive than fixed sets.

MF/HF
Medium Frequency/High Frequency radios are purpose-designed for long-distance communications between ships and between ships and shore. The range is virtually worldwide, in the right frequency band.

The downsides of MF/HF sets are the high price, complex installation that includes a tuneable antenna and earth plate, and atmospheric and electrical equipment noise.

LICENCES
The marine radio licencing situation is confusing. Under the Radiocommunications Act 1992, the operation of marine-radio equipment aboard any Australian vessel must be authorised by a licence. However, Class Licences are available for boats that have 27mHz and VHF radios, without application and are free of charge. Copies of the licence conditions can be downloaded from the Australian Communications Authority (ACA) website (www.aca.gov.au).

Boat owners are legally required to comply with the conditions of the Class Licence, particularly with respect to frequency use and transmitting power.

The confusing twist is that there is no operator licence requirement to use a 27mHz radio, but there is if you get on the air on a VHF unit. There are four classes of VHF licence and details can be sourced from the Australian Maritime College, PO Box 986, Launceston, Tasmania 7250.

MF/HF radios attract a ship station licence requirement, as well as an operator's licence. Ship station licence applications can be made to the ACA, and operator licence examinations are carried out under the aegis of the Australian Maritime College.

DISTRESS CALLS
Apart from the need to receive warnings and communicate with other boaties, most of us fit radios to be sure that we can summon help if required.

The 27mHz band isn't an official marine distress band, but it's monitored to some extent by Limited Coast Stations (LCS) that are operated by marine rescue organisations.

Channels 88 and 86 are the designated distress-call channels. VHF distress calls on Channel 16 are monitored around the clock by Coastal Radio Stations (CRS) in some locations on the Australian coast, and these CRS points also transmit weather reports on Channel 67. Limited Coastal Stations (LCS) monitor VHF distress channels 16 and 67 at certain times.

It's absolutely vital that boaties contact the CRS and LCS people in their area to ensure they know the local distress-channel monitoring procedures.

MF/HF radio users have the international distress-call channels 2182, 4125, 6215, 8291, 12 290 and 16 420 available, but the MCS at Wiluna and Charleville don't monitor voice transmissions on these frequencies. Distress calls to the MCS pair need to be via Digital Selective Calling (DSC).

The nine Coast Radio Stations (CRS) at major coastal centres maintain 24-hour listening watches on 4125, 6215, 8291 for distress and safety calls, and also broadcast navigation warnings on 8176.

Voice monitoring of 2182 is now done only at LCS locations. 

DIGITAL SELECTIVE CALLING
Digital Selective Calling (DSC) is an innovation that's intended to improve the reception of distress calls by replacing the human monitoring of radio equipment with an alarm. It's an intrinsic part of the Global Maritime Distress and Safety System (GMDSS).

DSC is intended to eliminate the problem of poor radio monitoring, which has resulted in many radio signals being unheard. It is also an automated way of establishing contact between radio stations, by transmitting a short burst of data that sounds an alarm in the receiving station.

In the case of distress alerts, all DSC stations receiving the alert will have their operator alarms sounded.

In Australia only the HF frequency, 4mHz upwards, has official DSC monitoring, although some other countries have DSC monitoring on MF and VHF frequencies as well. The top-tier Australian MCS receivers listen only for DSC transmissions, not voice signals or messages.

Many VHF radios now being sold in Australia have DSC, but this is not currently being monitored. VHF DSC is planned for Australian coastal waters in the future.

The DSC frequencies monitored by MCS in Australia are in the 4–16kHz band and are linked to the traditional distress voice channels. Once the DSC alert has been transmitted, voice communication is established by the MCS on the relevant distress call channel.

In addition to sounding the radio operator alarm when received by another radio station, the DSC alert also carries the transmitting station's identity code. This nine-digit Maritime Mobile Service Identity (MMSI) number carries information about the country of registration and the vessel.

DSC distress alerts carry the normal MMSI information, plus the position, either by GPS integration with the radio, or by manual entry.

INSTALLATION
Fitting a radio looks deceptively simple, but range and signal quality can be adversely affected by incorrect installation. If you're not absolutely sure you know all the pitfalls of DIY radio installation, you're better off paying a professional to install it.

We spoke to an old radio pro to get some idea of the areas most people go wrong, and his list was a long one - but most of the problems had to do with aerials.

It's common to see whip aerials braced against stanchions or flybridge struts, but binding an aerial to a metal post alters its effectiveness.

Another problem is UV deterioration, and most plastic aerials start to lose their efficiency after as little as a year's exposure to direct sunlight.

Insulators can crack or age and become ineffective. Another 'leakage' problem with insulators occurs if boat owners paint over them.

The coaxial cable attached to a 27mHz aerial is part of the aerial length calculation, so the cable shouldn't be shortened to avoid coiling it. A shortened aerial lead will reduce the efficiency of the whip.

It shouldn't need to be said, but the aerials for 27mHz, VHF and MF/HF radios aren't interchangeable - but people do try.

The additional power and clarity of a VHF transmitter over a 27mHz one can't be exploited if the aerial is positioned low down on the boat - as high as possible gives the best range.

MF/HF aerials are commonly backstay wire, with insulators top and bottom, but if the boat is dismasted the aerial goes with the stick. A backup whip aerial is essential for boats equipped with backstay aerials.

MF/HF radios won't work properly without earthing, but the earthing system is different from an electrical system, where fatter is generally better. The correct earth for an MF/HF radio is a broad, thin copper strip - the wider the better - leading to an earth plate on the hull. Because the current flow is only on the surface, the thickness of the copper earth lead doesn't matter.

RADIO OR MOBILE PHONE
The increasing use of mobile phones has made some boaties see their radios as somewhat redundant - particularly if the mobile is a satellite unit.

Mobiles work well where they have a signal - almost anywhere in the case of a satellite phone - but they're number specific. If you don't know the number to ring, the phone is useless.

Radios, on the other hand, are broadcast devices, with the possibility of sending a message to hundreds of different stations, simultaneously.

There's another, more practical reason for using a radio to request assistance rather than a mobile. Many police and rescue authorities are tired of hoax calls - the global statistic is that 97 per cent of 'distress' calls are false - and some authorities insist on marine-radio verification of a phone call for assistance.

But either way, a proper understanding of your radio is vital to your safety onboard.