Furuno 841, 821 manual Sweep Timing, Closing the Installation Menus

6)As a final test, move the boat towards a small buoy and confirm that the buoy shows up dead ahead on the radar when it is visually dead ahead.

5.8 Sweep Timing

This adjustment ensures proper radar per- formance, especially on short ranges. The radar measures the time required for a trans- mitted echo to travel to the target and return to the source. The received echo appears on the display based on this time. Thus, at the instant the transmitter is fired, the sweep should start from the center of the display (sometimes called sweep origin.)

A trigger pulse generated in the display unit goes to the antenna unit through the signal cable to trigger the transmitter (magnetron). The time taken by the signal to travel up to the antenna unit varies, depending largely on the length of signal cable. During this period the display unit should wait before starting the sweep. When the display unit is not adjusted correctly, the echoes from a straight local object (for example, a harbor wall or straight pier) will not appear with straight edges—namely, they will be seen as “pushed out” or “pulled in” near the pic- ture center. The range of objects will also be incorrectly shown.

(1) Correct	(2) Target pushed	(3) Target pushed
	inward	outward

Figure 5-21 Examples of improper and

correct sweep timings

1)Transmit the radar on the shortest range and adjust the sensitivity and STC.

2)Visually select a straight echo (harbor wall, straight pier).

3)Display the Installation Setup 2 menu and select Adjust Sweep Timing.

5)While looking at the target selected at step 2, press cursor pad at the 9 o’clock or 3 o’clock position to straighten the tar- get.

6)Press the [ENT] key.

5.9Closing the Installation Menus

Press the [MENU] key and turn off the power.

Table 5-1 Voltage ratings (reference for installer)

Item			MODEL			MODEL		Remarks
	821				841
Magnetron		TP804 #5		1.7-2.1V	TP803 #5		0.9-1.1V	Tx, long
current								range
Magnetron		TP804 #6		7.9-8.1V	TP803 #4		7.4-7.6V	Stand-by
heater
voltage
HV		TP804 #7		7.9-8.9V	TP803 #1		290-330V	Tx, long
								range

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