Furuno 841 User Manual download pdf (Page 18)

7

How to adjust A/C RAIN and FTC

(suppressing rain clutter)

The vertical beamwidth of the scanner is de-

signed to see surface targets even when the

ship is rolling. However, by this design the

unit will also detect rain clutter (rain, snow,

hail, etc.) in the same manner as normal tar-

gets. Figure 2-6 shows the appearance of rain

clutter on the display.

Adjusting A/C RAIN

When rain clutter masks echoes over a wide

range, raise the A/C RAIN slightly to dis-

tinguish targets from the clutter.

Appearance of

rain clutter

A/C RAIN adjusted;

rain clutter suppressed.

Figure 2-6 Effect of A/C RAIN

Adjusting FTC

To suppress rain clutter from heavy storms

or scattered rain clutter, adjust the FTC. The

FTC circuit splits up these unwanted ech-

oes into a speckled pattern, making recog-

nition of solid targets easier. FTC and

selected level appear at the top right-hand

corner of the display when the circuit is

turned on.

Note: In addition to reducing clutter, the FTC

can be used in fine weather to clarify the pic-

ture when navigating in confined waters. How-

ever, with the circuit activated the receiver is

less sensitive. Therefore, turn off the circuit

when its function is not required.

2.9 Tuning the Receiver

The receiver can be tuned automatically or

manually. For automatic tuning the receiver

is tuned each time you switch from stand-

by to transmit. For manual tuning, the re-

ceiver is properly tuned when the longest

tuning indicator appears. (However, the

length of the indicator changes with the num-

ber of radar echoes, range and other factors.)

Figure 2-7 Tuning indicator

Manual tuning

The default tuning method is automatic. To

switch to manual tuning;

1) Press the [MENU] key to open the menu.

2) Press the cursor pad to select Tuning.

3) Press the cursor pad to select MANUAL.

4) Press the [ENT] key followed by the

[MENU] key.

How to tune manually

While pressing and holding down the [HM

OFF] key, press the 9 o'clock or 3o'clock

position on the cursor pad to tune. Tune to

show the longest tuning indicator.

1.5

NM

0.5

AUTO

Tuning

indicator

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