Added offshore safety via HF DSC


Most voyagers are familiar with digital selective calling (DSC) on their VHF radios, but many may not be aware that DSC is available on high-frequency (HF) marine SSB as well. Most HF DSC equipment adds thousands of dollars to an HF SSB installation. Now there’s a PC software-based product that adds HF DSC to your marine SSB for less, giving ocean sailors added safety benefits in a distress situation. Called Personal DSC, the product from High Seas Radio ( is priced at $599.

Commercial vessels larger than 300 gross tons are required by international law to carry HF DSC equipment. Voyaging boats have no such requirement and, since few voyagers wish to spend the money required for such a setup, HF DSC is a rarity on most live-aboard vessels. Yet the safety aspect of HF DSC is a valuable one. HF DSC is part of the Global Maritime Distress and Safety System (GMDSS), a set of international requirements for communications gear and protocols designed to improve the ability of search and rescue forces to aid mariners in distress. The main thrust of GMDSS is for large commercial vessels, yet voyaging boats can also take advantage of parts of the system. 

The elements of GMDSS are: 

• Emergency position indicating radio beacons (EPIRBs) 
• Navtex (an automated text-based warning and information system via radio at 518 kHz)
• Inmarsat satellite communications capability (either Inmarsat B, Fleet 77 or Inmarsat C)
• Search rescue radar transponders (SARTs) 
• Electrical power requirements
• MF, HF and VHF DSC radio gear

Few voyaging boats have Navtex gear, Inmarsat installations, SARTs or the type of robust electrical generation and battery storage systems large ships are required to carry. The two most common elements of GMDSS employed by voyagers are EPIRBs and VHF DSC. With a product like Personal DSC, voyagers can add HF DSC to their vessel’s arsenal of safety gear less expensively than with HF DSC hardware found on larger vessels. 

This screenshot shows a Personal DSC message log. The highlighted message was acknowledged by WLO in New Orleans.

To use VHF DSC, voyagers need a maritime mobile service identity (MMSI) number. This MMSI is attached to the vessel, so employing HF DSC doesn’t require a second MMSI. 

One of the elements of DSC is the way DSC radios relay messages. “The primary advantage of HF DSC is safety,” said Richard Duncan, founder of High Seas Radio LLC, which offers the Personal DSC product. “It sends a digital distress message that is relayed by the radios of other ships and shore stations until it gets to the Coast Guard. It can relay a message all the way around the world.” There is no special training required to use HF DSC, and you don’t need to have a ham radio license. “This has nothing to do with ham radio,” said Duncan. “This system operates on marine HF SSB frequencies.” 

To use Personal DSC, you need a Windows-based PC (it won’t run on a Mac) equipped with a sound card and an interface box that connects the PC to the radio (you also need a GPS position input). According to High Seas Radio, a typical interface box is a Signalink USB unit that provides the sound card for the computer and radio transmit control to the transceiver. The speaker out/mic in can also be used with other interface boxes. It’s also important that the transceiver and antenna must be capable of operating on the desired DSC frequencies. 

The actual Personal DSC product is a software program that is installed on the PC; there is also a dongle box that connects via USB. It holds the software license and your MMSI number. This means you can install the software on multiple PCs and just transfer the dongle to whichever PC you want to use (although MMSI numbers are specific to a particular vessel so you can’t use the same MMSI on different vessels). 

Other uses for HF DSC beyond safety involve sending messages to coastal stations requesting communications (such as a connection to land telephone number), or sending a message to, say, the Coast Guard that you would like non-emergency info or communications and, of course, calling other vessels via their MMSI number. The moderator of an ad hoc cruising network can call a number of boats at once using the DSC group call feature.  

HF DSC joins other safety-related tools available to voyagers when they are sailing offshore, including EPIRBs, satphones, non-DSC HF radio and satellite communicator units like the inReach.

By Ocean Navigator