One of the most important pieces of safety equipment on board your catamaran is your two-way radio. A marine VHF radio is different from other VHF radios used for land or air communications. Marine radios are specifically designed for communications on the waterways. They are installed on all large ships and most seagoing small craft, and with slightly different regulation on rivers and lakes. Not all VHF radios are designated for marine use. It is important that you use two-way radios specifically approved for marine use when on the waterways. Other VHF radios should not be used as they will not have the proper frequency settings. Also, today’s marine radios have other features such as NOAA weather alert channels that would not be available on land mobile VHF radios.
The Global Maritime Distress and Safety Program – GMDSS, operates on terrestrial and satellite technology. Terrestrial and satellite telecommunications include VHF radiotelephony, VHF DSC digital selective calling.
Marine VHF radio
refers to the radio frequency range between 156 and 174 MHz, inclusive. The “VHF” signifies the ”very high frequency” of the range. Modern-day marine VHF radios offer not only basic transmit and receive capabilities. Permanently mounted marine VHF radios on seagoing vessels are required to have certification of some level of “Digital Selective Calling” (DSC) capability. This allows a distress signal to be sent with a single button press. Marine VHF radio equipment is installed on all catamarans for rent in Croatia. It is also used, with slightly different regulation, on rivers and lakes. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbors, locks, bridges, and marinas.
A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 (156.8 MHz) is the international calling and distress channel. Transmission power ranges between 1 and 25 watts. Giving a maximum range of up to about 60 nautical miles (111 km) between aerials mounted on tall ships and hills, and 5 nautical miles (9 km; 6 mi) between aerials mounted on catamarans at sea level. Frequency modulation (FM) is used, with vertical polarization, meaning that antennas have to be vertical in order to have good reception.
VHF radio in Croatia
The Republic of Croatia is a signatory of the International Convention on Maritime Search and Rescue. As such it is a part of the Global Maritime Distress and Safety System – GMDSS. The National Maritime Rescue Coordination Center Rijeka (MRCC RIJEKA) provides a 24-hour watch service. In terms of jurisdiction of the Center, this includes the region of internal marine waters, territorial waters of the Republic of Croatia (marine belt wide 12 nautical miles from the shoreline towards the open sea) and the region of international waters as confirmed in treaties with neighboring states and as reported to the International Maritime Organization (IMO). Internal maritime waters and territorial marine waters are divided into sub-regions, for which the sub-centers are responsible alongside the MRCC RIJEKA.
The National Center (MRCC RIJEKA), all the sub-centers (Port Authorities) and their port stations and all shore radio stations – Rijekaradio, Split radio and Dubrovnikradio, provide maritime radio monitoring services on internationally confirmed frequencies and channels for emergencies and safety.
Weather radio broadcasts
Marine VHF radios can also receive weather radio broadcasts, where they are available. Shore-based radio stations emit daily weather reports and weather forecasts for the upcoming 12 and 24 hour periods, both in Croatian and in English:
- Rijeka radio – call sign 9AR – VHF ch. 04, 20, 24, 81 at 5:35, 14:35, 19:35 UTC
- Split radio – call sign 9AS – VHF ch. 07, 21,23, 81 at 5:45, 12:45, 19:45 UTC
- Dubrovnik radio -call sign 9AD – VHF ch. 07,04 at 6:25, 13:20, 21:20 UTC
Constant weather forecasts on VHF – transmitters
Weather forecasts for the Croatian coastal region are provided in Croatian, English, Italian and German every ten minutes, and are updated at 7:00, 13:00 and 19:00 (local time). The summary presents an overview of the weather, a short forecast for the next 24 hours and information on air pressure. Broadcast on:
- VHF ch. 73 for northern Adriatic/ western coast of Istria
- VHF ch. 69 for northern Adriatic/ eastern part
- VHF ch. 67 for central Adriatic / eastern part
- VHF ch. 73 for southern Adriatic / eastern part