19.18 Frequency tuningThe frequency is dependent on the sonar moduleand transducer in use. When using a non-CHIRPsonar module or a CHIRP sonar module that isoperating in non-CHIRP mode then the transducer’sfrequency can be manually fine-tuned.The advantages of being able to tune the frequencyinclude:• Optimization for particular species of fish andwater conditions.• Avoiding interference from other sonar operatingnearby (at the same frequency).• Use of wide or narrow beam on a particulartransducer.Traditional and Legacy frequency tuningThe following frequency types are available onLegacy and Traditional sonar modules:• Auto — When operating in automatic nofine-tuning is needed as the system will set thefrequency automatically to suit your transducer’soperating conditions.• Lower frequencies — (e.g. 50 kHz) — Producesa wide sonar beam and penetrate the water well.Lower frequencies provide a lower resolutionimage that may not be as good at detecting smallfish. Use lower frequencies if you require a largecoverage beneath your vessel or if you are in deepwater.• Higher frequencies — (e.g. 200 kHz) —Produces a narrow beam and produce a highresolution image. They are most useful inshallower water (up to 1000 ft) and at higherspeeds.The graph below depicts fine-tuning of a Traditionalor Legacy sonar frequency (from –50% to +50%).Low HighSensitivity (dB)Frequency-50% +50%D12574-21231. Tuning range2. Transducer characteristics3. Operating frequencyCHIRP frequency tuningThe list below provides details of the frequency typesavailable when using a CHIRP sonar module.• Auto — When operating in automatic nofine-tuning is needed as the system will set thefrequency automatically to suit your transducer’soperating conditions.• Low frequency — non-CHIRP mode (e.g. 50 kHz)— Produces a wide sonar beam and penetratethe water well. Lower frequencies provide a lowerresolution image that may not be as good atdetecting small fish. Use lower frequencies if yourequire a large coverage beneath your vessel or ifyou are in deep water.• Medium frequency — non-CHIRP mode (e.g. 90kHz) — Produces good detail at most depths, withmoderately wide sonar beam.• High frequency — non-CHIRP mode (e.g. 160kHz) — Produces a narrow beam and producea high resolution image. They are most usefulin shallower water (up to 1000 ft) and at higherspeeds.• Low Chirp — CHIRP mode (e.g. 42 to 65 kHz) —No fine-tuning is not needed as the CHIRP sonarmodule will sweep the transducer’s availablefrequency range in each ping.• Med Chirp — CHIRP mode (e.g. 85 to 135 kHz)— No fine-tuning is not needed as the CHIRPsonar module will sweep the transducer’s availablefrequency range in each ping.• High Chirp — CHIRP mode (e.g. 130 to 210 kHz)— No fine-tuning is not needed as the CHIRPsonar module will sweep the transducer’s availablefrequency range in each ping.With the CHIRP sonar module set to a non-CHIRPmode the frequency can be fine tuned to adjust thefrequency at which the transducer is transmitting.The graph below depicts fine-tuning of a CHIRPbroadband sonar frequency (from —50% to +50%).Low HighSensitivity (dB)Frequency D12575-23-50% +50%1 21. Tuning range2. Transducer characteristics3. Operating (center) frequencyFine-tuning the sonar frequencyWhen connected to a Traditional or Legacy sonarmodule or when operating a CHIRP sonar modulein non-CHIRP mode the transmit frequency can befine-tuned.From the Fishfinder application:1. Ensure that the channel frequency that you wantto fine-tune is displayed in the active Fishfinderpane.2. Select Menu.3. Select Set-up.4. Select Sounder Set-up.5. Select Tune Frequency.The frequency adjust control is displayed.6. Adjust the frequency until optimum results areachieved.276 gS Series
