Eagle Electronics 502cDF manual How Eagle Sonar Works, Position points

Position points:	1,000 waypoints; 1,000 event marker icons.
Audible alarms:	Arrival/off-course/anchor.
Graphic symbols for
waypoints or event
marker icons:	42.
Routes:	100, up to 100 waypoints per route.
Plot Trails:	10 savable; up to 10,000 points per trail.
Zoom range:	40 ranges; 0.02 to 4,000 miles.

NOTE:

The above memory capacities refer only to the unit’s on-board mem- ory. The amount of GPS or sonar data you can record and save for recall later is limited only by the number and size of the MMC cards you have.

NOTICE!

The storage temperature range for your FishElite 502c iGPS and SeaCharter 502cDF iGPS is from -4 degrees to +167 degrees Fahr- enheit (-20 degrees to +75 degrees Celsius). Extended storage 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. Customer service numbers are listed on the last page of this manual.

How Eagle 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 under water 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. Here's how it locates the bottom and finds 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

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