Eagle Electronics Cuda 240 S/GPS manual How Your Sonar Works, How Your GPS Works

Plot Trails: ...................... 10 savable; up to 9,999 points per trail.

Zoom range:.................... 39 ranges; 0.02 to 4,000 miles.

NOTICE!

The storage and operation temperature range for your unit is from -4 degrees to +167 degrees Fahrenheit (-20 degrees to +75 degrees Celsius). Extended storage or operation in temperatures higher or lower than specified will damage the liquid crystal display in your unit. This type of damage is not covered by the warranty. For more information, contact the factory's Customer Service Department; phone numbers are listed on the last page.

How Your Sonar Works

Sonar has been around since the 1940s, so if you already know how it works, skip down to read about the relatively new technology of GPS. But, if you've never owned a sonar fish finder, this segment will tell you the underwater basics.

Sonar is an abbreviation for SOund NAvigation and Ranging, a technol- ogy developed during World War II for tracking enemy submarines. A sonar consists of a transmitter, transducer, receiver and display. In simple terms, here's how it finds the bottom, or the fish:

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 sonar unit can record a log of the sonar signals that scroll across the screen and save them in its memory. (These recordings are also called sonar charts or sonar graphs.) You can replay this sonar log in the unit using the Sonar Simulator function. You can save several different sonar log files, erase 'em and record new ones, over and over again.

How Your GPS Works

You'll navigate faster and easier if you understand how this unit scans the sky to tell you where you are on the earth — and, where you're go- ing. (But if you already have a working understanding of GPS receivers and the GPS navigation system, skip on ahead to Section 2, Installation

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