Humminbird 858c Combo Operation Manual page 12

When all the echoes are viewed side by side,
an easy to interpret "graph" of the bottom, fish
and structure appears.
The sound pulses are transmitted at various
frequencies depending on the application.
Very high frequencies (455 kHz) are used for
greatest definition, but the operating depth is
limited. High frequencies (200 kHz) are
commonly used on consumer sonar and
provide a good balance between depth
performance and resolution. Low frequencies
(83 kHz) are typically used to achieve greater
depth capability.
Introduction 2
The power output is the amount of energy
generated by the sonar transmitter. It is
commonly measured using two methods:
• Root Mean Square (RMS) measures power
output over the entire transmit cycle.
• Peak to Peak measures power output at the
highest points.
The benefits of increased power output are
the ability to detect smaller targets at greater
distances, ability to overcome noise, better
high speed performance and enhanced depth
capability.