Single sideband radio: still making waves
5/17/2021

Back in the late 1970s when I started covering marine topics, radio communication was pretty much limited to two main players: VHF and single sideband (SSB). VHF served well for short distance ship to ship and sometimes ship to shore. SSB took over for longer distance communications. Today, satellite-aided communication and cell phones have joined VHF as the primary tools for keeping recreational boaters in touch. To the surprise of many, SSBs are still in service on commercial vessels and some distant-water cruisers. For boaters who aren’t familiar with the technology, here’s a primer written for a recent issue of Marine Electronics Journal.


By John Barry


The single sideband radio, also known as MF/HF (medium frequency/high frequency) radio, is a great addition to many boats. For commercial vessels, an SSB is required for sailing outside of Sea Area A1, or 25 miles offshore. Although SSB radios are fairly rare on pleasure boats, there are some cool applications for them as well.

The primary advantage of an SSB is range. At 150 watts and depending on antenna an SSB develops a ground wave of over 100 miles, often 200 miles. This allows direct radio communication over that range. And because of the frequencies used by SSB, the radio signal also bounces off the ionosphere, allowing for global communications.

SSB radios are ham radios for boats. We use the even MHz frequencies for SSB—2, 4, 6, 8 MHz, etc. HAM radio uses the odd MHz frequencies. The global communication capacities of SSB are why SSB is mandatory equipment on many vessels. Recreational boats that cruise offshore or globally also benefit from these capabilities. There is a lot to SSB. Operating a radio of this type is quite technical, requiring use of different frequencies at different times of day. The installing technician should advise new SSB owners they need to be educated on operation in order to benefit from this great device.

When a radio transmits, it sends radio frequencies through the coax (transmission line) to the antenna. The energy starts as electrostatic energy. When the antenna resonates and photons are generated, the energy becomes electro-magnetic energy. This is like a stereo and a speaker, the energy in the speaker wire (transmission line) is electrostatic; you cannot hear it. Once it hits the speaker, it becomes electromagnetic energy and a sound wave can be heard. Audio is reflected (echo) absorbed (sound insulation) or bent (horn effect). Radio waves are also subject to reflection, absorption and direction by conductors (metal) within the radio wave. Radio propagation is beyond the scope of this article.
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