Skippers who possess years of experience in using scanning sonar have few issues with interpreting the display, but newcomers might find it difficult, says Eric Kunz, senior product manager for Furuno USA. This is particularly true when it comes to searchlight sonar, which Kunz likens to rotating a flashlight on a stick.
Searchlight models like the CH-270 rotate relatively slowly, taking as long as 64 seconds to make a full-circle sweep, or “train,” as it is called, at the maximum range of 2,500 feet. This is because the CH-270 samples in relatively thin sectors — some as narrow as 6 degrees — at a time. It waits for each return before moving on to the next sector.