Furuno 1823C manual Dual-frequency display LF picture, HF picture, Marker-zoom display

4. VIDEO SOUNDER OPERATION

Dual-frequency display

The dual-frequency display provides both LF and HF pictures. This display is useful for comparing the same picture with two different sounding frequencies.

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LF	HF

Dual-frequency display

LF picture

The sounder uses ultrasonic pulses to detect bottom conditions. The lower the frequency of the pulse, the wider the detection area. Therefore, the low frequency is useful for general detection and judging bottom condition.

HF picture

The higher the frequency of the ultrasonic pulse the better the resolution. Therefore, the high frequency is ideal for detailed observation of fish school.

low frequency

high frequency

Sounding area and transmission frequency

Marker-zoom display

The marker-zoom display expands a selected area of the normal sounder picture to full vertical size of the screen on the left-half window. You may specify the portion to expand by operating the VRM (Variable Range Marker), which you can shift with the [ENTER] knob. The area between the VRM and zoom marker is expanded. The length of the segment is equal to one division of the depth scale.

Note: The VRM is set independently from other displays in case of multiple displays.

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