RadioReference Wiki:Ka3jjz

The HF Maritime Communications Receiver

A receiver for monitoring HF maritime communications must have the following features:

• Coverage from 100 kHz to 30 MHz
• Upper sideband (USB) and lower sideband (LSB) modes
• Good stability (doesn't drift off frequency)
• Good selectivity (able to seperate 2 stations that are close to one another in frequency)

Many receivers and portables marketed as shortwave or world band radios will satisfy these requirements. The majority of voice communications use USB, but LSB is certainly possible (foreign fishing fleets have been known to use LSB); therefore, whatever you select must have USB and LSB capabilities. The lower band limit of 100 kHz is typical of many HF radios, but many marine transmissions occur at 2 MHz and above. Other features such as memory channels and alpha tagging are desirable, but not necessary. See the Receiver Reviews article for several links on this important topic.

Propagation and Antennas

Your ability to receive HF maritime communications is affected by signal propagation conditions in the atmosphere. Many factors affect propagation, including sunspots, solar flares, and the time of day. Frequencies above 10 mhz or so are usable during the local daytime, while frequencies below 10 mhz will be usable at night. If you are a newcomer to this topic, reading a good primer would be a great benefit. Don't get discouraged about all the jargon; whole books and very technical scientific papers have been written on the subject; but it's unnecessary to have a degree to gain a basic understanding. To get you started, please see the Propagation Primer website by Geoffrey Noles AE4RV (requires Flash player).

Your station is only as good as the antenna you can use. The best antennas for receiving HF maritime comms is going to depend largely on what you can put up and what kind of receiver you are using. Generally, something that is relatively broadbanded - such as a random wire or inverted L - will be the best one to get you started. Our HF Antennas page has a number of possibilities, including some that are already assembled - all you need to do is supply the feedline and proper connectors.

If you live in an urban area, or are plagued with noise problems, consider utilizing a loop antenna. MW DXers have been utilizing loops for their directional capabilities almost since the beginning of the broadcast industy; they are useful for HF listening because they are less sensitive to certain kinds of electrical noise. If you're interested in this topic, please see our Loops page.

Another possibility is to use a Magnetic Longwire Balun(MLB) with a good grade of coax to feed an inverted L design. Plans exist on building baluns on the Shortwave SWL Antenna Yahoo group; or you can purchase the popular PAR EF-SWL antenna, which uses a similar principle. The HF Antennas article has information on these topics as well.