Humminbird 200DX - Manual (Page 17)

USING THE 200DX USING THE 200DX
HOW SONAR WORKS
HOW SONAR WORKS
Your Humminbird unit uses sonar to locate and define
underwater objects, define the bottom terrain, as well as
determine distance.
Sonar technology is based on sound waves. Your
Humminbird unit sends out a sound wave signal. With this
signal it determines distance by measuring the time
between the transmission of the sound wave and when the
sound wave is reflected off an object. Your Humminbird
uses the reflected signal to interpret location, size and
composition of an object.
Sonar is very last. A sound wave can travel from the surface to a depth of 240’ (70m)
and back again in less than 1/4 of a second. It is unlikely that your boat can “outrun" this
sonar signal.
The 200DX is a dual frequency, dual beam unit, and generates two distinct sonar
signals - one narrow, one wide. Each signal is optimized for a particular purpose. First,
the center beam transmits at a frequency of 200kHz in a 20 degree (narrow)
symmetrical pattern for greater depth capability and excellent detail. Information from
this center beam is used to draw the graphic representation of the bottom on the
display.
Second, the wide beam transmits at a frequency of 83kHz in a 53 degree (wide)
symmetrical pattern for greater area of coverage. Information from the wide beam is
used to accurately detect the presence and location of fish. A wide beam has a large
area of (coverage but limited resolution of detail. A narrow beam has excellent detail,
but within a limited area of coverage.
The combination of the two beams and dual frequencies provides the combination of a
large area of coverage and a high level of detail.