Wesmar HD800/45-14 Installation & Operation Manual page 22

Depending on need and application, a shorter pulselength
will give better target defi nition off the bottom, shore,
and working close to the surface.
When 0 pulselength is selected, the transmitter is turned
off. The sonar then operates in a passive mode, listening
only. Sonar targets will not exist. Zero pulselength is
excellent for troubleshooting vessel vibration, propeller,
engine and electrical noise.
Pulse can be selected separately for sonar and bottom
profi le.
Example: Set pulselength as short as possible for bottom
profi le to spot fi sh closest to the bottom. Set pulselength
longer for sonar when scanning long range.
12.4 TVG (TIME VARIABLE GAIN)
Function 4- TVG BOX highlighted, left of screen.
(TVG can be selected separately for sonar and bottom
profi le.)
Press up or down on the SELECT SWITCH to select
100 through 2000.
Normal TVG settings:
FREQUENCY
180 kHz
160 kHz
110 kHz
60 kHz
45 kHz
27 kHz
TVG (Time Variable Gain) offsets the effects of propa-
gation loss of sound as it passes through the water.
Propagation Loss of sound is the sum of Spreading
and Attenuation Losses. Spreading Loss refers to the
physical spreading of sound energy as it travels outward
from the source and back from the target. Attenuation
Losses are primarily due to absorption and the scattering
of sound as it passes through the water.
Spreading Loss is a constant where the sound energy
decreases as the square of the range. The type of loss is
also called inverse-square or spherical spreading losses.
Page 22
HD800
MILLISECONDS
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