Raymarine c125 Installation And Operation Instructions Manual Download

Page: 286 / 464

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%).

Low

High

)

Frequency

-50%

+50%

D12574-2

Tuning range

Transducer characteristics

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

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%).

Low

High

)

Frequency

D12575-2

-50%

+50%

Tuning range

Transducer characteristics

Operating (center) frequency

Fine-tuning the sonar frequency

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