User guide

901-10037001/1.1 FS 20/25 Operators Manual
Page 5.12 Maintenance and Troubleshootin
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Kongsberg Simrad Mesotech Ltd.
Port Coquitlam, BC - Canada
5.4.3 Trawl Cable Gain
Signals passing through a length of cable are attenuated by an amount dependent
on the type and length of cable used. The FS Trawl Monitoring system will apply
gain to the signals to compensate for the cable losses.
With both the FS20 and FS20/25 systems, the cable gain compensation has been
automated. Each time the system is powered up (or when a system calibration is
performed), the gain levels are set in the PWR/TTM unit translation module LF1 and
LF2 Sub-assemblies by the processor unit. The transmit pulses from the sonar
heads are monitored and the gain is increased until the received signal is normalized
to a standard level. That is why you hear the transducers pinging during the system
calibration sequence.
The resulting gain is displayed in the Head Settings Window as two integer values
separated by a comma. Each value is an integer from 0 to 255, with a larger value
corresponding to higher gain. The values each represent an 8-bit number that is
used to establish the gain levels on the LF1 and/or LF2 Telemetry Sub-assemblies.
You can observe the Head Setting Window by “Clicking” on “View”, highlighting
“Display” and then “Clicking” on “Head Settings”.