The transmitter emits an electrical impulse, which the transducer con- verts into a sound wave and sends into the water. (The sound frequency can't be heard by humans or fish.) The sound wave strikes an object (fish, structure, bottom) and bounces back to the transducer, which converts the sound back into an electrical signal.
The receiver amplifies this return signal, or echo, and sends it to the display, where an image of the object appears on the scrolling sonar chart. The sonar's microprocessor calculates the time lapse between the transmitted signal and echo return to determine the distance to the object. The whole process repeats itself several times each second.
Your LMS-480 can record a log of the sonar signals that scroll across the screen and save them to the MMC memory card. (These recordings are also called sonar charts or sonar graphs.) You can replay this sonar log in the unit using the Sonar Simulator function, or play it back on a personal computer using our free Sonar Viewer. The viewer is available for download from the Lowrance web site, www.lowrance.com.
You can save several different sonar log files, erase 'em and record new ones, over and over again. The size of your sonar recordings is only limited by the free space available on your MMC.
How LMS-480 GPS Works
You'll navigate faster and easier if you understand how the LMS-480 scans the sky to tell you where you are on the earth — and, where you're going. (But if you already have a working understanding of GPS receivers and the GPS navigation system, skip on ahead to Section 2, Installation & Accessories on page 13. If you're new to GPS, read on, and you can later impress your friends with your new-found knowledge.)
First, think of your LMS-480 as a small but powerful computer. (But don't worry — we made the LMS-480 series easy to use, so you don't need to be a computer expert to find your way!) The unit includes a keypad and a screen with menus so you can tell LMS-480 what to do. The screen also lets LMS-480 show your location on a moving map, as well as point the way to your destination.
This gimbal-mounted unit uses an external antenna/receiver module, which makes the whole system work something like your car radio. But instead of your favorite dance tunes, this receiver tunes in to a couple of dozen GPS satellites circling the earth. (It will also listen in to the WAAS satellites in orbit, but more about that in the upcoming segment introducing you to GPS and WAAS.)
Your LMS-480 listens to signals from as many satellites as it can "see" above the horizon, eliminates the weakest signals, then computes its
