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Simrad SN90 Operator Manual
Selecting operating frequency for minimum noise
The
function is used to control the centre frequency of the acoustic
Frequency
transmissions (pings). The centre frequency can be changed from 70 to 120 kHz in steps
of 1 kHz. All types of noise matter when you wish to find the best operating frequency.
Context
A lower frequency gives you a better detection range because the attenuation loss is
smaller. A higher frequency gives you better range resolution. A higher frequency also
gives you narrower beams and a "sharper" image".
Noise from internal and external sources have an impact on the choice of operating
frequency. One specific frequency may perform better than the others on your vessel.
To measure the noise level, observe the value presented on the
dialog box.
We recommend that you do this test twice. First, do the test with all other hydroacoustic
systems (echo sounders, ADCP, sonars) turned off. Second, do the test with normal
operating conditions. This allows you to see how the other hydroacoustic systems affect
the SN90 operation.
Procedure
1
On the
menu, select
Main
a
Select
SN90 Factory Default
b
Select
Activate Selected Setting
c
Select
OK
2
On the
menu, set
Main
3
Open the
Operation
4
Open the
Active
5
Open the
Setup
6
Select
to open the dialog box.
BITE
a
Select
Noise
b
Select
Start Noise Measurements
c
On the
Active
value.
d
Note frequencies with high noise levels, and try to avoid using them.
Tip
The factory default settings include operating frequency. If you apply these settings
remember to make the appropriate changes afterwards.
44
User Settings
.
.
to apply your changes and close the
to 1000 m.
Range
menu. Set
Tx Power
menu. Set
Pulse Type
menu.
to open the page.
menu, change the
.
User Settings
to Off.
to CW Medium.
.
setting while observing the noise
Frequency
page in the
Noise
BITE
dialog box.
381295/B
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