Safeguarding essential communications at sea

Coastguard agencies across the globe work 24/7 to protect lives at sea including responding to vessels with problems, collisions and medical incidents at sea. Some agencies may also be tasked with sea border security responsibilities and pollution control e.g. responding to oil spills.

Coast Guard

To effectively carry out this role, they are reliant on robust communications systems and protocols. These are typically dependent on MF, HF and VHF frequency bands which are vulnerable to interference. Ensuring the emergency distress channels remain reserved for Mayday calls only and are not congested or interfered with is particular crucial to ensure incidents at sea can be identified and responded to as quickly as possible.

Regulations are in place setting out the proper use of different channels, but these are not always respected. Sometimes this may be uninformed users or foreign nationals who may be used to a different channel allocation. On other occasions, radio equipment may be broken or  interference may be malicious e.g. hoax Mayday calls.

If emergency channels are blocked it is important to resolve the interference as quickly as possible to avoid genuine incidents being missed and lives being lost. If there is no response to radio calls, it may be necessary to use radio monitoring and direction finding to locate and visit the responsible vessel.

Locating interference sources on land and at sea

Radio monitoring and direction finding equipment can be used for the fast resolution of interference cases and identification of those responsible for malicious activity.

Using our direction finding RFeye Arrays, a bearing indicating the direction of a radio signal (such as a VHF marine radio transmission) can be generated. A single Array can be placed on a land-based vehicle or a boat allowing a target to be homed in on using our Cumulative Tracking technology. Fixed Arrays can also be placed at locations along the coast to provide a 24/7 radio monitoring and direction finding capability. By using two or more Arrays, an instant location can be determined using our AOA geolocation capability.

Using this technology, malfunctioning radios which may be transmitting continuously can be located allowing the coastguard to visit the vessel and warn the owner. Hoax transmissions which are coming from land can also be located allowing suspects to be apprehended by law enforcement. Where vessels in distress are unsure of their location, the direction finding system can also be used to support rescue operations.

Additional benefits of the solution

Direction finders can also be used for general radio monitoring. This might include carrying out an annual survey of maritime frequencies to assess which channels are congested and which are under-utilized. The system could also be used to track ship AIS (Automatic Identification System) signals verifying locations and preventing spoofing.

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