VHF Radio with DSC – A Key Safety Tool at Sea

VHF (Very High Frequency) radio is an indispensable communication tool at sea, playing a crucial role in ensuring safety and efficient communication between vessels and coastal stations. In today’s world, where communication technologies are continuously evolving, VHF remains the foundation of maritime radio communication. Its reliability, ease of use, and broad applicability make it an essential piece of equipment for any vessel – from commercial ships to recreational boats.

In this article, you will learn how VHF radios with DSC (Digital Selective Calling) work, the key principles of their use, and the regulations governing their use on vessels, whether commercial, passenger, or recreational.

What is a VHF Radio with DSC?

A VHF radio with DSC is a modern communication device that enables digital transmission of calling signals, including alarms, safety signals, and distress calls. DSC speeds up and simplifies communication in emergency situations. Not only does it transmit a call signal, but it also automatically provides the vessel’s location, thanks to its connection with a GPS receiver. This makes a VHF radio with DSC a fundamental but critical component of maritime safety systems.

How to Use a VHF Radio with DSC?

Check the Correctness of the MMSI Number

Each VHF radio with DSC must be assigned to a vessel through a unique MMSI (Maritime Mobile Service Identity) number. The MMSI is a nine-digit number that identifies the vessel in the DSC system and is essential for establishing communication and sending distress signals. Make sure the MMSI number is correctly programmed in the radio. An incorrectly entered MMSI number can cause identification issues during emergency situations.

Check the GPS Position Accuracy

The DSC function works with the onboard GPS receiver. Therefore, it is advisable to regularly check if the VHF radio is receiving GPS signals correctly and displaying the vessel’s current position. In an emergency, sending an incorrect location automatically could delay the rescue operation. Make sure the device is properly connected to the GPS and updates the location in real time.

Regularly Test the DSC Function

Internal Test

VHF radios with DSC have self-test options that check the internal components of the DSC system. Perform this test regularly to ensure the radio is functioning properly. If any issues are found, the system should report errors, allowing for quick corrective action.

External Test

To ensure your radio works properly under real conditions, regularly test the DSC system by sending a test signal to other vessels or coastal stations. You can use the ITU database to find MMSI numbers of coastal stations that respond to DSC signals. The database is available at https://www.itu.int/mmsapp/coaststation/list.

Test the system regularly, especially before longer voyages, to ensure that the DSC system is fully operational.

Using DSC in Emergency Situations

The DSC function can save lives in an emergency. If needed, press the “Distress” button, which will automatically send a distress signal along with your GPS location (if the device is connected to GPS). However, make sure the situation truly requires immediate assistance before using this function.

How to Check Voice and DSC Communication in a VHF Radio? (Step by Step)

Step 1: Checking Voice Communication

  1. Turn on the VHF radio: Ensure the device is correctly powered on and the antenna is properly connected.
  2. Select a working channel: Choose the appropriate channel for voice calls.
  3. Prepare a list of vessels you can test with. Suitable vessels can be found using an AIS system, for example.
  4. Call the vessel or coastal station: Use standard communication phrases, such as “This is vessel [Your name] calling [Target vessel name], over.”
  5. Check signal quality: Ensure the sound quality is clear, without interference.
  6. End the call: Conclude the conversation using standard protocol, for example, “This is vessel [Your name], out.”

Step 2: Verifying the DSC Function

  1. Check the MMSI number: Ensure the MMSI number in the radio is correct.
  2. Check the GPS position: Ensure the radio is receiving GPS signals and displaying the current position.
  3. Perform an internal test: Select the self-test option from the radio’s menu.
  4. Perform an external test: Choose a coastal station and send a test DSC signal.
  5. Receive confirmation: Wait for confirmation from the target vessel.

For example, we will use the SAILOR 6222 VHF DSC Class A radio.

First, on the main screen, check the correctness of the MMSI and GPS position.

To run the DSC self-test procedure, follow these instructions:

  1. Press the SETUP button. If you do not see it on the display, press the MORE button until the SETUP option appears.
  2. Press the arrow button to navigate to DSC SETUP.
  3. Turn the selection knob to choose DSC Self Test. Press and turn the knob to select RUN. The test will check the DSC encoding/decoding capability at the RF level. The radio will automatically send a test DSC call to its own MMSI number without activating the transmitter’s power amplifier. At the same time, the radio will receive and compare the received call with the one sent. The test result will be displayed on the screen.
  4. Press the OK button to confirm the test result and return to normal operation.

Important: If the DSC loop test fails, this means that the DSC functionality is not working correctly, including the ability to send a DISTRESS (emergency) message.

If you want to conduct a DSC test call with another vessel or a coastal station, follow these simple steps:

  1. Press the CALL button.
  2. Use the dial to select the call type: SAFETY TEST.
  3. In the TO: field, enter the 9-digit MMSI number of the vessel you want to contact, or use the phone book (PHBOOK) to select a contact.
  4. Press the SEND button to send the call.
  5. Wait for confirmation.

Important: If you do not receive confirmation for a long time, it does not necessarily mean your radio is malfunctioning. Contact the coastal station to verify if they received and confirmed your DSC call. If they confirm a problem, call technicians to check the device’s functionality.

SOLAS Regulations for VHF Radios with DSC

According to the International Convention for the Safety of Life at Sea (SOLAS), the requirements for VHF radios with DSC are found in Chapter IV – Radiocommunications, specifically in Regulation 7. These requirements apply not only to commercial vessels but also to passenger ships, commercial yachts, and recreational vessels exceeding certain sizes or operating in international waters.

Who is Affected by the Regulations?

  • Passenger ships: All passenger vessels, regardless of size or area of operation, must have a VHF radio with DSC.
  • Cargo ships of gross tonnage over 300: Cargo ships over 300 tons operating in international waters must have VHF with DSC.
  • Commercial yachts and recreational vessels: In some countries, recreational vessels and commercial yachts must meet the same standards as larger ships.

These regulations stem from the international GMDSS safety system, which requires communication systems, including VHF radios with DSC, on maritime vessels.

Conclusion

A VHF radio with DSC is an advanced tool that enhances safety at sea. Regular checks of voice communication and the DSC system, testing the MMSI number, GPS connection, and adhering to SOLAS regulations are key to maintaining safety on international waters. Remember to follow guidelines and test your equipment regularly.

If you need reliable radiocommunication equipment or technical support for the repair and installation of navigation devices, Sharp Horizon offers a wide range of solutions tailored to the needs of marine vessels. Contact us to learn more!