Frequency Tuning - Lighthouse a65 Installation And Operation Instructions Manual

19.18 Frequency tuning

The frequency is dependent on the sonar module
and transducer in use. When using a non-CHIRP
sonar module or a CHIRP sonar module that is
operating in non-CHIRP mode then the transducer's
frequency can be manually fine-tuned.
The advantages of being able to tune the frequency
include:
• Optimization for particular species of fish and
water conditions.
• Avoiding interference from other sonar operating
nearby (at the same frequency).
• Use of wide or narrow beam on a particular
transducer.
Traditional and Legacy frequency tuning
The following frequency types are available on
Legacy and Traditional sonar modules:
• Auto — When operating in automatic no
fine-tuning is needed as the system will set the
frequency automatically to suit your transducer's
operating conditions.
• Lower frequencies — (e.g. 50 kHz) — Produces
a wide sonar beam and penetrate the water well.
Lower frequencies provide a lower resolution
image that may not be as good at detecting small
fish. Use lower frequencies if you require a large
coverage beneath your vessel or if you are in deep
water.
• Higher frequencies — (e.g. 200 kHz) —
Produces a narrow beam and produce a high
resolution image. They are most useful in
shallower water (up to 1000 ft) and at higher
speeds.
The graph below depicts fine-tuning of a Traditional
or Legacy sonar frequency (from –50% to +50%).
1. Tuning range
2. Transducer characteristics
3. Operating frequency
CHIRP frequency tuning
The list below provides details of the frequency types
available when using a CHIRP sonar module.
• Auto — When operating in automatic no
fine-tuning is needed as the system will set the
frequency automatically to suit your transducer's
operating conditions.
• Low frequency — non-CHIRP mode (e.g. 50 kHz)
— Produces a wide sonar beam and penetrate
the water well. Lower frequencies provide a lower
resolution image that may not be as good at
Fishfinder application
-50% +50%
1
2
3
detecting small fish. Use lower frequencies if you
require a large coverage beneath your vessel or if
you are in deep water.
• Medium frequency — non-CHIRP mode (e.g. 90
kHz) — Produces good detail at most depths, with
moderately wide sonar beam.
• High frequency — non-CHIRP mode (e.g. 160
kHz) — Produces a narrow beam and produce
a high resolution image. They are most useful
in shallower water (up to 1000 ft) and at higher
speeds.
• Low Chirp — CHIRP mode (e.g. 42 to 65 kHz) —
No fine-tuning is not needed as the CHIRP sonar
module will sweep the transducer's available
frequency range in each ping.
• Med Chirp — CHIRP mode (e.g. 85 to 135 kHz)
— No fine-tuning is not needed as the CHIRP
sonar module will sweep the transducer's available
frequency range in each ping.
• High Chirp — CHIRP mode (e.g. 130 to 210 kHz)
— No fine-tuning is not needed as the CHIRP
sonar module will sweep the transducer's available
frequency range in each ping.
With the CHIRP sonar module set to a non-CHIRP
mode the frequency can be fine tuned to adjust the
frequency at which the transducer is transmitting.
The graph below depicts fine-tuning of a CHIRP
broadband sonar frequency (from —50% to +50%).
-50%
1
1. Tuning range
2. Transducer characteristics
3. Operating (center) frequency
Fine-tuning the sonar frequency
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When connected to a Traditional or Legacy sonar
module or when operating a CHIRP sonar module
in non-CHIRP mode the transmit frequency can be
fine-tuned.
From the Fishfinder application:
1. Ensure that the channel frequency that you want
to fine-tune is displayed in the active Fishfinder
pane.
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 are
achieved.
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+50%
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