Humminbird HELIX 9 Operation Manual page 30

Down Imaging Sonar (HELIX DI GPS)
45°
455kHz
16°
455kHz
28°
200kHz
75 Degree Total Coverage
CHIRP Sonar (HELIX CHIRP GPS)
If your transducer is also a CHIRP transducer, you can operate the down beams at different frequency ranges. CHIRP sonar beams
provide conical coverage directly below the boat for depths up to 1500 feet (500 m) (HELIX CHIRP GPS and HELIX CHIRP SI GPS) or
600 feet (183 m) (HELIX CHIRP DI GPS). CHIRP sonar sends continuous sonar pulses at varying frequencies to provide more detailed
returns and better target separation. CHIRP applies to the down beams only.
For example, if you have a CHIRP SI transducer connected, you can select a Medium or High Frequency for the down beams and then
select the start frequency and end frequency using the CHIRP Frequency Spectrum menu. See Set Up Sonar: Select CHIRP
Frequencies.
HELIX CHIRP Sonar
20˚
200kHz
60˚
83kHz
Sonar Overview
The Down Imaging transducer scans the water with razor-thin, high-definition
beams. The beams are wide (side to side) but very thin front to back.
The Down Imaging beams (shown in green) can be operated at two frequencies:
455 kHz (75°) or 800 kHz (45°). Select 455 kHz for the best overall image quality
and depth. Select 800 kHz for the sharpest image. See Set up Sonar for more
800kHz
information.
75°
The transducer also uses conical beams to provide data in traditional 2D format
(shown in magenta and yellow). Select 455 kHz for a narrowly focused 16° center
beam, or select 200 kHz for a wider 28° beam (see Set up Sonar and Sonar
Overview).
HELIX CHIRP SI Sonar
20˚
200kHz
60˚
83kHz
30
HELIX CHIRP DI Sonar
16°
455kHz
28°
200kHz
7