Frequency Tuning - Raymarine a65 Operation Instructions Manual

2. Select Shallow so that On is highlighted.
Selecting Shallow will switch between On and Off.
3. Select Shallow Limit.
The shallow limit numeric adjust control is
displayed.
4. Adjust the setting to the required value.
5. Select Ok to confirm the new value and close the
numeric adjust control.
Note: The Shallow Limit cannot be set to greater
than the Deep Limit.
Fishfinder application

15.20 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
-50% +50%
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