Ask Sail: Dockside Interference
Rene Etherton of Chicago, Illinois asks:
When I’m at sea and at anchor, my audio system plays great, and my new digital TV converter gives me great HD reception on my new HD LCD screen. But at the dock I get a loud hum on my audio system, and my over-the-air reception “breaks apart” on most of my favorite TV stations. What gives?
Gordon West replies:
The hum on your audio system comes from your onboard battery charger. The temporary cure is to simply switch off the charger when listening to your audio system. Ultimately, you may wish to run it off an isolated battery of its own, possibly charged with a solar panel.
As for your television, this is a common problem caused by multi-path reception, where signals bounce around nearby buildings and off the masts around you. With an analog television, you’d see a faint ghost and snow behind the picture. The digital converter, however, gets overwhelmed by the multiple signals it is receiving out of phase, and instead of showing you a ghost, it freezes for a few seconds and displays a “no signal” message. There is no good way to cure this if you’re keeping your boat in a downtown marina, so you’d best go sailing!