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HF Maritime Communications

From The RadioReference Wiki

HF Maritime communications have undergone a radical change over the last several years. Many stations that used to have voice communications have either gone dark or using digital modes, some of which are not readable except to the intended target. Let's take a look at what is out there.

Voice

  • Although most voice communications are gone, there are some stations still on the air. Ships and stations are allocated in fixed frequency ranges, and you can find those ranges listed here.
  • The Canadians have the Radio Aids to Navigation
  • USCG Voice Marine weather broadcasts can be found here. Click the USCG HF Voice link


Digital (below the AM broadcast band)

  • NOTE: Unless notes otherwise, the links for the various modes comes from the Signal Identification Wiki
  • Navigational aids such as DGPS are slowly dying out. The US discontinued its DGPS support as of the 30th of June 2020.
  • SITOR-B/NAVTEX broadcasts are quite plentiful, and there is a wide range of software that can decode them. The main issue with receiving these broadcasts lie with the typical receiver; sensitivity is generally reduced in this band because of a perceived lack of interest (due to the lack of broadcasts in North America on this band) as well as reducing the possibility of mixing products from the MW band appearing here (which it does anyway). SDRs may need some front end preselection to prevent overload in areas where there are many MW stations (such as those found in urban areas). Active Loops are commonly used to hear these broadcasts.

Drift Net Buoys and Navigational Aids

  • Like DGPS, the navigational aids found in the 1700-1800 Khz range are also slowly dying out and being replaced with satellite tracking.

Digital (2-30 Mhz)


Websites


How to Find Activity?

The spectrum for HF maritime communications is very wide. Unlike VHF/UHF scanning, it's challenging to automatically scan a segment of the band because HF noise will always be present. While some maritime stations are on a fixed schedule, others (such as fishing fleets) are much more difficult to detect due to their transient nature; thus, listening for maritime comms can be a game of patience. The more time passes, the harder it is to hear again. Mailing lists are one of the best ways to keep ahead of what is being heard, as traffic can be passed relatively quickly. See the Utility Related Clubs, Mailing lists and Publications of the Utility_Monitoring article for some suggested resources


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