By Ed Sherman
Lots of Flat Copper Strap in Your Boat? Think Single-Sideband Radio
Counterpoise is a familiar concept to SSB operators, but most used-boat buyers are likely to wonder what all that flat copper is for.
Question: I recently bought a used cruising sailboat and have been crawling around in the bilge and behind-the-scenes areas to get to know it better and see where I can store things without interfering with systems.
One thing I’ve noticed is that there is a lot of flat copper strapping, as shown in the photo I sent in. It’s located throughout the boat and actually connected to things like through-hull fittings and such. What is this stuff for anyhow?
Answer: I’ll bet your new-to-you boat is equipped with a single-sideband radio (SSB), or, if it’s not installed now, was at some point before you purchased the boat. This flat copper is often used for what is known as an antenna counterpoise. The copper acts as a substitute for earth or ground as part of an antenna system. It’s unique to wire or whip antennas, and is a necessary component for the antenna to be effective. Basically the counterpoise allows the antenna to “see” an image of itself, effectively reflecting and transmitting the radio signals. Without an effective counterpoise of ground plane, the SSB antenna will not function. If the counterpoise doesn’t have adequate exposed copper surface area, then the range of the SSB will be greatly affected. This is a case where more exposed surface area is always better.
To learn more about all of this, get a copy of my book, Advanced Marine Electrics and Electronics Troubleshooting available through International Marine or Amazon.com.
- Ed Sherman is a regular contributor to boats.com, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. Ed’s blog posts appear courtesy of his website, EdsBoatTips.