C

9 - 5 2 , A s h i h a r a - c h o , N i s h i n o m i y a , J a p a n

A l l r i g h t s r e s e r v e d . Printed in Japan

P U B . N o . O M E - 3 4 8 1 0

Y o u r L o c a l A g e n t / D e a l e r

DANGER

Before turning on the radar make sure no one is near the scanner unit.

Prevent the potential risk of someone begin struck by the rotating antenna and exposure to RF radiation hazard.

WARNING

Use the proper fuse.

Fuse rating is shown in the chapter 5.

Use of a wrong fuse can result in equipment damage

Do not operate the equipment with wet hands.

Electrical shock can result.

WARNING

Do not open the equipment.

Improper handling can result in electrical shock. Only qualified personnel shold work inside the equipment.

Do not disassemble or modify the equipment.

Fire electrical shock or serious injury can result.

Turn off the power immediately if water leaks into the equipment or the equip- ment is emitting smoke or fire.

Continued use of the equipment can cause fire or electrical shock.

Do not place liquid-filled containers on the top of the equipment.

Fire or electrical shock can result if a liquid spills into the equipment.

CAUTION

Do not use the equipment for other than its intended purpose.

Use of the equipment as a stepping stool, for example, can result in personal injury or equipment damage.

No one navigation device should ever be solely replied upon for the navigation of a vessel.

Always confirm position against all available aids to navigation, for safety of vessel and crew.

Two warning labels are attached to the display unit and scanner unit. Do not remove these labels. If labels are peeling off or are illegible, contact

a FURUNO agent or dealer.

<Scanner Unit>

Name: Radiation Warning Label

Type: 03-142-3201-0

Code no.: 100-266-890

WARNING

Radiation hazard. Only qualified personnel should work inside scanner. Confirm that TX has stopped before opening scanner.

Congratulations on your choice of the FURUNO MODEL 1761 MARK-3 Marine Ra- dar. We are confident you will see why the FURUNO name has become synonymous with quality and reliability.

For over 50 years FURUNO Electric Com- pany has enjoyed an enviable reputation for innovative and dependable marine electron- ics equipment. This dedication to excellence is furthered by our extensive global network of agents and dealers.

Your radar is designed and constructed to meet the rigorous demands of the marine en- vironment. However, no machine can per- form its intended function unless properly installed and maintained. Please carefully read and follow the recommended proce- dures for installation, operation and mainte- nance.

While this unit can be installed by the pur- chaser, any purchaser who has doubts about his or her technical abilities may wish to have the unit installed by a FURUNO representa- tive or other qualified technician. The impor- tance of a through installation can not be overemphasized.

We would appreciate hearing from you, the end-user, about whether we are achieving our purposes.

Thank you for considering and purchasing FURUNO equipment.

Features

Your radar has a large variety of functions, all contained in a remarkably small cabinet.

The main features of the MODEL 1761 MARK-3 are:

??Traditional FURUNO reliability and qual- ity in a compact, lightweight and low-cost radar.

??Durable brushless antenna motor.

??On-screen alphanumeric readout of all op- erational information.

??Standard features include EBL (Electronic Bearing Line), VRM (Variable Range Marker), Guard Alarm, Display Off Cen- ter, and Echo Trail.

??Watchman feature periodically transmits the radar to check for radar targets which may be entering the alarm zone.

??Ship???s position in latitude and longitude, range and bearing to a waypoint, and ship???s speed/heading/course can be shown in the bottom text area. (Requires a navigation aid which can output such data in IEC 61162 format.)

??Zoom feature provided.

2.21 Adjusting Control Panel Brilliance ......

3. FALSE ECHOES

4. MAINTENANCE & TROUBLE-

SHOOTING

1.1 What is Radar?

The term ???RADAR??? is an acronym meaning RAdio Detection And Ranging. Although the basic principles of radar were developed dur- ing World War II, echoes as an aid to naviga- tion is not a new development.

1.2How Ships Determined Position Before Radar

Before the invention of radar, when running in fog near a rugged shoreline, ships would sound a short blast on their whistles, fire a shot, or strike a bell. The time between the origination of the sound and the returning of the echo indicated how far the ship was from the cliffs or the shore. The direction from which the echo was heard indicated the rela- tive bearing of the shore.

1.3How Radar Determines Range

Radar determines the distance to the target by calculating the time difference between the transmission of a radar signal and the recep- tion of the reflected echo. It is a known fact that radar waves travel at a nearly constant speed of 162,000 nautical miles per second. Therefore the time required for a transmitted signal to travel to the target and return as an echo to the source is a measure of the dis- tance to the target. Note that the echo makes a complete round trip, but only half the time of travel is needed to determine the one-way distance to the target. This radar automati- cally takes this into account in making the range calculation.

1.4How Radar Determines Bearing

The bearing to a target found by the radar is determined by the direction in which the ra- dar scanner antenna is pointing when it emits an electronic pulse and then receives a re- turning echo. Each time the scanner rotates pulses are transmitted in the full 360 degree circle, each pulse at a slightly different bear- ing from the previous one. Therefore, if one knows the direction in which the signal is sent out, one knows the direction from which the echo must return.

1.5Radar Wave Speed and Scanner Rotation Speed

Note that the speed of the radar waves out to the target and back again as echoes is extremely fast compared to the speed of ro- tation of the scanner. By the time radar ech- oes have returned to the scanner, the amount of scanner rotation after initial transmission of the radar pulse is extremely small.

1.6 The Radar Display

The range and bearing of a target is displayed on what is called a Plan Position Indicator (PPI). This display is essentially a polar dia- gram, with the transmitting ship???s position at the center. Images of target echoes are re- ceived and displayed at their relative bear- ings, and at their distance from the PPI center.

With a continuous display of the images of targets, the motion of the transmitting ship is also displayed.

A

Targets

DA

Heading marker

Range and bearing of a target, relative to own ship, are readable on the PPI.

D

Turns power on.

Press together with [STBY/TX] key to turn power off.

Alternates between stand-by and transmit.

Lights (in green) to show the radar is in the "echonomy (stand-by)" mode.

Adjusts the brightness of the screen.

Selects radar range.

The "+" and "-" touchpads select a higher and lower range, respectively. Selets items during the menu display.

RANGE

(Control) Adjusts sensitivity of radar receiver.

(Switch) 1. Temporarily erases heading marker.

2.Change + cursor data from R/B to L/L and vice versa.

(Control) Reduces sea clutter caused by waves.

(Switch) Turns on/off the radar target plotting

(Control) Reduces rain clutters. (Switch) Suppresses heavy

precipitation.

Shifts the display; turns the zoom function on, and restores normal picture, in that order.

Turns the Electronic Bearing

Line (EBL) on and off.

Turns on and off the guard zone alarm.

SHIFT

ZOOM

EBL

GUARD

RING Turns the fixed range rings on and off.

VRM Turns the Variable Range Marker

(VRM) on and off.

MENU

Turns the menu display on and off.

Trackball

(1)Shifts cursor, EBL and VRM.

(2)Sets guard zone.

(3)Selects items and options on menu.

(4)Shifts origin of EBL and VRM.

2.2 Turning the Radar On/Off

After confirming there are no crew near the scanner unit, press the [POWER] key to turn on the power.

The front panel will light up. The magnetron takes about two minutes and thirty seconds to warm up before the radar can be oper- ated. The time remaining for warm up of the magnetron appears at the center of the dis- play, counting down from 2:29 to 0:01.

To turn off the radar, press the [POWER] and [TX] key together.

2.3 Transmitting

After the power is turned on and the magne- tron has warmed up, the message ???ST-BY??? (Stand-By) appears at the center of the dis- play, showing the radar is ready to transmit. However, no targets will appear on the screen until the radar is transmitting by pressing the [TX] key (TX is short for ???transmit). In stand- by the radar is available for use at anytime - but no radar waves are being transmit.

2.4Stand-by

When you won???t be using the radar for an extended period, but you want to keep it in a state of readiness, place it in stand-by by pressing the [TX] key. The display shows ???STBY,??? (default setting) or goes into the economy mode. (You can select stand-by condition on the menu. )

Economy mode

The CRT can be set to automatically turn it- self off when in stand-by, to reduce power consumption. This feature is called the ???economy mode???. When the economy mode is on, the ???ECONOMY??? indication under the [TX] key lights.

2.5Selecting the Range

The range selected automatically determines the fixed range ring interval, the number of fixed range rings, pulselength, and pulse rep- etition rate, for optimal detection in short to long ranges. The range and ring interval ap- pear at the top left corner of the display.

Selecting the range

Press the [- RANGE +] key. The range and range ring interval appear at the top left cor- ner on the display.

Tips for selecting the range

???When navigating in or around crowded harbors, select a short range to watch for possible collision situation.

???If you select a lower range while on open water, increase the range occasionally to watch for vessels that may be heading your way.

2.6Adjusting Picture Brilliance

The [BRILL] key adjusts the brilliance of the radar picture in eight levels.

Press the [BRILL] key to set the brilliance level.

2.7Adjusting Receiver Sensitivity

The [GAIN] control adjusts the sensitivity of the receiver. It works in precisely the same manner as the volume control of a broadcast receiver, amplifying the signals received.

The proper setting is such that the back- ground noise is just visible on the screen. If you set up noise is just visible on the screen. If you set up for too little sensitivity, weak echoes may be missed. On the other hand excessive sensitivity yields too much back- ground noise; strong targets may be missed because of the poor contrast between desired

echoes and the background noise on the dis- play.

To adjust receiver sensitivity, transmit on long range, and adjust the [GAIN] control so back- ground noise is just visible on the screen.

Tips on adjusting GAIN

???In certain circumstances it may be useful to reduce the gain slightly to improve range resolution, clear up the picture, or reduce clutter caused by rain or snow.

???Range resolution is a measure of the ca- pability of a radar to display as separate pips the echoes received from two targets which are on the same bearing, and are close together radially. With reduction in the gain setting, the echoes may be made to appear as separate pips on the display.

???When sailing or cruising in crowded re- gions a slight reduction in gain often helps to clear up the picture. This should be done carefully, otherwise weak targets may be missed.

???Echoes from ships inside a squall or storm may be obscured if the gain is at its nor- mal setting, since the clutter may have masked, but not completely, echoes from the targets.

Note: In all cases, return the gain to its origi- nal position after any temporary reduction is no longer required.

How the A/C SEA control works

The [A/C SEA] control reduces the amplifi- cation of echoes at short ranges (where clut- ter is the greatest) and progressively increases amplification as the range in- creases, so amplification will be normal at those ranges where there is no sea clutter.

Adjusting the A/C SEA control

The proper setting of the A/C SEA should be such that the clutter is broken up into small dots, and small targets become distinguish- able.

If the control is set too low, targets will be hidden in the clutter, while if it is set too high, both sea clutter and targets will disappear from the display. In most cases adjust the control until clutter has disappeared to lee- ward, but a little is still visible windward.

1.Confirm that the sensitivity is properly ad- justed, and then transmit on short range.

2.Adjust the [A/C SEA] control so small tar- gets are distinguishable but some clutter remains on the display.

2.8Adjusting the A/C SEA Control

(reducing sea clutter)

Echoes from waves can be troublesome, cov- ering the central part of the display with ran- dom signals known as ???sea clutter???. The higher the waves, and the higher the antenna above the water, the further the clutter will extend. Sea clutter appears on the display as many small echoes which might affect radar performance. (See the left-hand figure in Figure 2-2.) When sea clutter masks the picture, adjust the A/C SEA control to reduce the clutter.

Figure 2-2 How to adjust the A/C SEA control

Tip for adjusting the A/C SEA

A common mistake is to over-adjust the cir- cuit so all the removed. As an example set up for maximum A/C SEA. You will see how the center of the display becomes dark. This dark zone can be dangerous (targets may be missed), especially if the sensitivity is not properly adjusted. Always leave a little clut- ter visible on the display to be sure weak echoes will not be suppressed. If there is no clutter visible on the display, turn off the cir- cuit.

2.9Adjusting the A/C RAIN Control

(reducing rain clutter)

The vertical beamwidth of the antenna 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 2-3 shows the appearance of rain clutter on the display.

Adjusting A/C RAIN

When rain clutter masks echoes, adjust the [A/C RAIN] control. This control splits up these unwanted echoes into a speckled pat- tern, marking recognition of solid targets easier.

Figure 2-3 Effect of A/C RAIN

Note: In addition to reducing clutter, the [A/C RAIN] control can be used in fine weather to clarify the picture when navigating in confined waters. However, with the circuit activated the receiver is less sensitive. Therefore, turn off the circuit when its function is not required.

2.10 Adjusting FTC

To suppress rain clutter from heavy storms or scattered rain clutter, press the [A/C RAIN] control ([FTC] switch). The FTC circuit splits up these unwanted echoes into a speckled pattern, marking recognition of solid targets easier. ???FTC??? appears 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. However, with the circuit activated the re- ceiver is less sensitive. Therefore, turn off the circuit when its function is not required.

2.11 Tuning the Radar Receiver

The radar receiver is tuned automatically each time you turn on the power, thus there is no front panel control for adjustment of the receiver. To show the automatic tuning cir- cuit is working, a tuning bar displays tuning condition.

2.12Erasing the Heading Marker

The heading marker may occasionally mask a target. To view the target, you can tempo- rarily erase the heading marker by pressing and holding down the [GAIN (HM OFF)] con- trol. Release the control to re-display the markers.

Heading

marker

Figure 2-4 Heading marker

2.13Select the Cursor Data Display

When connecting with NAV (IEC61162 for- mat) and gyro converter (IEC61162 or AD- 10 format), this radar can show the cursor position by Latitude/longitude at bottom of screen.

Each time pressing [HM OFF] key, the data will change from Range/Bearing to Latitude/ longitude and vice versa.

When the cursor position is displayed by Lati- tude/Longitude, pressing the [HM OFF] key outputs L/L data of the cursor position (TLL) to the plotter. Then Range/Bearing are dis- played instead of L/L.

2.14Turning the Range Ring On/Off

When range rings obscures a target, you can erase them by pressing the [RING] key.

2.15 Measuring the Range

You can measure the range to a target three ways: by the range rings, by the cursor, and by the VRM (Variable Range Marker).

Measuring range by range rings

Count the number of rings between the cen- ter of the display and the target. Check the range ring interval and judge the distance of the echo from the inner edge of the nearest ring.

To turn the rings on or off, press the [RING] key.

Measuring range by cursor

Operator the trackball to place the cursor in- tersection on the inside edge of the target echo. The range to the target, as well as the bearing, appears at the bottom of the display.

Measuring by VRM

1.Press the [VRM] key to display a VRM. (The VRM is the dotted ring.)

2.Place the VRM on the inside edge of the target by operating the trackball.

3.Press the [VRM] key again to fix the VRM to the position.

4.Check the range readout to find the range to the target. To erase the VRM, press and hold down the [VRM] key for about three seconds.

Range

6.0 NM Range ring 2.0

interval

Cursor

Figure 2-5 Measuring Range by the Cursor and the VRM

Unit of range measurement

You can display the range readouts of the VRM and the cursor in nautical miles or kilo- meters. This is done at installation.

2.16 Measuring the Bearing

There are two ways to measure the bearing to a target: by the cursor, and by the EBL (Electronic Bearing Range).

Measuring bearing by cursor

Operate the trackball to bisect the target with the cursor intersection. The bearing to the target appears at the bottom of the display.

Measuring by EBL

1.Press the [EBL] key to display an EBL. (The EBL is the dotted line.)

2.Position the EBL so it bisects the target by operating the trackball.

3.Press the [EBL] key again to fix the EBL to the position.

4.Check the bearing readout to find the bearing of the target. To erase the EBL, press and hold down the [EBL] key for about three seconds.

MAG (or GYRO) BEARING*

6.0 NM MAG115.0??

2.0

Target

Cursor

EBL

???Bearings of stationary or slower moving targets are more accurate than bearings of faster moving targets.

???To minimize bearing errors keep echoes in the outer half of the picture by chang- ing the range scale; angular difference becomes difficult to resolve as a target approaches the center of the display.

2.17Shifting and Zooming the Display

The [SHIFT/ZOOM] key has two functions: display shifting and display zoom. Each time the key is pressed the function changes in the following sequence.

Normal Shift Zoom

Figure 2-7 SHIFT/ZOOM key sequence

Shift

Figure 2-6 Measuring Bearing by the EBL and Cursor

The bearing measured by the cursor or the EBL can be displayed in relative or true bear- ings (heading sensor or gyrocompass con- nection required). Relative bearings are relative to the bow of the vessel, and true bearings are relative to the True North. The indication ???MAG??? (or GYRO???) and the head- ing sensor (or gyrocompass) bearing (your ship???s bearing) appear at the top of the screen.

Note that the bearing to the cursor always varies with trackball operation. The EBL and its indication, however, are automatically fixed when the [EBL] key is pressed or 10 seconds elapses without trackball operation.

Tips on measuring bearing

???Bearing measurements of smaller targets pips are more accurate; the center of larger target pips is not as easily identi- fied.

2-6

The own ship???s position can be shifted to any position within the current range. The primary advantage of the shifted display is that for any range setting, the view ahead of your own ship can be extended without changing the range.

Place the cursor on area you wish to shift to the screen center and then press the [SHIFT/ ZOOM] key. The indication ???SHIFT??? appears. To restore normal operation press the key twice.

Note: If the cursor is not within the current range when the key is pressed, an audible beep sounds and the outermost range ring blinks twice , even if the range rings are off.

Zoom

The zoom feature allows you to double the area between own ship and an arbitrary lo- cation, to take a closer look at an area of in- terest without changing the range.

1.Operate the trackball to place the cursor on the target you want or area you want to zoom.

2.Press the [SHIFT/ZOOM] key. The indi- cation ???ZOOM??? appears and brinks.

3.To turn off the zoom, press the [SHIFT/ ZOOM] key again, or change the range.

(Normal display)

Place cursor where desired.

Cursor

2.18 Menu Operation

The menu, consisting of 9 items, mostly con- tains less-often used functions which once preset do not require regular adjustment. To open or close the menu, press the [MENU] key. You can select menus by using the trackball, then select item with the [RANGE] key.

Note: Current selections shown in reverse video.

Press the [SHIFT/ZOOM] key.

Press the [SHIFT/ZOOM] key.

Press the [SHIFT/ZOOM] key.

Figure 2-8 Shifting and zooming the display

2.19 Echo Stretch

Normally, the reflected echoes from long dis- tance targets appear on the screen as weaker and smaller blips even through they are com- pensated by the radar???s internal circuitry. The Echo Stretch function magnifies these small blips.

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

2.Operate the trackball to select ???1. ECHO STRETCH???.

3.Press the [RANGE] key to select ???ON???.

The indication ???ES??? appears at the upper right-hand side of the screen and the echoes are doubled lengthwise.

To turn off the echo stretch, select ???OFF??? on the MENU display.

Note 1: This function magnifies not only tar- gets but also sea clutter and radar interfer- ence are properly adjusted before activating the echo stretch.

Note 2: This function is inactivate on short ranges, that is 0.25 to 1 nautical miles. ???ES??? appears in reverse video when the echo stretch is turned on in those ranges.

2.20Suppressing Radar Interference

Radar interference may occur when near an- other shipborne radar operating in the same frequency band as your radar. Its on-screen appearance is many bright dots either scat- tered at random or in the form of dotted lines extending from the center (or the edge) to the edge (or the center) of the display. Fig- ure 2-11 illustrates interference in the form of curved spokes, Interference effects are distinguishable from normal echoes because they do not appear in the same place on suc- cessive rotations of the scanner.

Figure 2-10 Radar interference

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

2.Operate the trackball to select ???2. I. RE- JECT???.

3.Press the [RANGE] key to select ???ON???. (Factory setting is ON.)

The indication ???IR??? appears at the upper right- hand side of the screen. Press the [MENU] key again to erase the menu display.

2.21Adjusting Control Panel Brilliance

Adjusts the backlighting of the front panel in five steps.

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

2.Operate the trackball to select ???3. PANEL DIMMER???.

3.Press the [RANGE] key to select level de- sired.

4.Press the [MENU] key again to erase the menu.

2.22 Selecting Ranges

This radar has 14 ranges, some which you may not require. You can select or deselect ranges as follows.

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

2.Operate the trackball to select ???6. RANGE???.

3.Press the [RANGE] key to place the un- derline under the range you want to se- lect or deselect.

4.Press the [RING] key to select or dese- lect.

5.Repeat step 4 and 5.

Maximum number of ranges is all ranges. Minimum number of ranges is two.

2.23EBL/Cursor Bearing Reference

EBL and cursor bearing can be displayed relative to own ship???s heading (Relative) or with reference to North (True).

Note: Magnetic compass or gyrocompass connection required for true bearing.

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

2.Operate the trackball to select ???9. EBL/ +CURSOR???

3.Press the [RANGE] key to select ???TRUE??? or ???REL (Relative)???.

2.24 Guard Alarm

The alarm allows the operator to set the de- sired range (0 to maximum range) and bear- ing (0 to 360 degrees) for a guard zone, called Auto In/Out alarm. When ships, islands, land- masses, etc. go into (or go out of) the guard zone an audible alarm sounds to call the operator???s attention.

Before setting the alarm, be sure the [GAIN] control is properly adjusted, because the au- dible alarm sounds when the fifth or more level quantization echoes go into or go out of the guard zone.

1.Mentally create the guard zone you want to display on-screen. See Figure 2-12.

2.Set upper (lower) left edge of the guard zone with the cursor, and press the [GUARD] key.

The indication ???*GUARD??? (asterisk blink- ing) appears at the upper right-hand side of the screen. See Figure 2-12 (2). The asterisk indicates the guard zone is par- tially set, but the alarm function has not been actuated. It disappears once the guard zone is set completely.

3.Moving the trackball clockwise, set the lower (upper) right edge of the guard zone. The guard zone now appears on the display and alarm function has been actuated, See Figure 2-12 (3).

Note: To create a 360 degree guard zone, rotate the cursor counterclockwise instead of clockwise.

4.Press the [GUARD] key again. The as- terisk disappears and the alarm function is actuated after three to five antenna scannings, and then, the indication ???GUARD??? is replaced by ???G(IN)??? or ???G(OUT)???.

5.Any ships, landmasses, etc. coming into or going out of the guard zone will trigger the audible alarm. If the audible alarm sounds you can silence it by pressing the [GUARD] key. When this is done the indi- cation ???GUARD??? appears in reverse video.

6.Press the [GUARD] key again to restore the audible alarm. ???GUARD??? lights in nor- mal video.

7.To cancel both the guard zone and the audible alarm, press and hold down the [GUARD] key for three seconds.

Note 1: When the range is less than the half of the guard zone range, the guard zone dis- appears from the screen and ???UP RANGE??? indication appears. If this happens, select a range which will again display the guard zone on the screen.

Note 2: A target echo does not always mean a landmass, reef, ships or surface objects but can imply returns from sea surface or pre- cipitation. As the level of these returns varies with environment, the operator should (prop- erly) adjust the A/C SEA, A/C RAIN, FTC and GAIN to be sure target echoes within the guard zone are not overlooked by the alarm system.

Note: The audible alarm does not sound for the target originally existing the zone.

Case 2: When no targets exist inside the zone, the alarm zone is automatically set to ???Auto In Alarm??? mode and the indication ???GUARD??? is replaced by ???G (IN)???. The au- dible alarm sounds only on targets which go into the zone. See Figure 2-13 (2).

Asterisk blinking

Dashed line: no alarm

Guard zone

Figure 2-12 Auto In/Out Alarm

Guard zone

Figure 2-11 Setting Guard Zone

2.25Watchman

The watchman function turns on the radar and transmits its for about 30 seconds at a predetermined interval to check for targets

Cin a guard zone. This feature is useful when you do not need the radar???s function continu- ously but want to be alerted to radar targets in an area.

When the watchman feature is on, an inter- nal timer turns on the radar every 5, 10 or 20 minutes and the radar transmits for 30 sec- onds to check for the existence of radar tar- gets in a guard zone.

Auto In/Out Alarm

When the guard zone is set completely, the radar starts searching for targets inside the guard zone for 8 to 12 seconds. The indica- tion ???GUARD??? appears during this period.

Case 1: When there are targets inside the zone, the alarm zone is automatically set to ???Auto Out Alarm??? mode and the indication ???GUARD??? is replaced by ???G (OUT)???. The au- dible alarm sounds only on targets which go out of the zone or disappear. See Figure 2- 13 (1).

Watchman starts.

Figure 2-13How watchman works

1.Determine the guard zone (usually 360 degrees) with the guard alarm function.

2.Press the [MENU] key to open the menu.

3.Operate the trackball to select ???7. WATCHMAN??? .

4.Press the [RANGE] key to select a trans- mission interval.

5.Press the [MENU] key to actuate the watchman mode. The indication ???WATCH- MAN??? appears and the radar transmits for one minute and then turns to stand-by, and ???ECHONOMY??? lights.

Note: The antenna radiator does not rotate in the ???ECHONOMY??? (stand-by) mode. How- ever, the radiator rotates continuously dur- ing the watchman mode.

6.The radar automatically starts transmit- ting after the time selected at step 4 has passed. It transmits for one minute ap- proximately and examines the guard zone for change.

(a)If the condition is unchanged, the ra- dar automatically returns to stand-by again and continues operating in the watchman mode.

(b)If the condition differs from the previ- ous one, the radar sounds an audible alarm, cancels the watchman mode and transmits continuously.

7.To cancel the watchman mode manually, press any key.

2.26 Plotting

This function plots the movement of other ships relative to your own ship.

Press the [PLOT (A/C RAIN)] control to start plotting. The indication ???PLOT??? and a timer appear at the top right-hand corner of the screen and movement of all targets is plot- ted. The timer counts up from 0:01 to 99:59, whereupon the timer indication freezes but plotting continues. Targets initially are up- dated every 15 seconds. However, you can select intervals of 30 seconds, 1 minute, 3 minutes or 6 minutes through the MENU dis- play (Refer to Chapter 3). The plotting inter-

val (except for 15 seconds) appears to the right of the indication PLOT.

If the range is changed during plotting, plot- ting begins anew with the newly selected range. To cancel plotting, press the [PLOT] key.

Plotting Interval

(30 sec., 1min.,3min., 6min.)

Timer

Figure 2-14 Plotting Indications

Plot Brilliance

The brilliance of plotted echoes is selectable through the MENU display. Press the [MENU] key and select ???5. PLOT BRILLIANCE???.

2.27 Navigation Data Display

Navigation data can be displayed on the screen if your radar receives navigation in- put form a Loran-C, NNSS (satellite naviga- tor) or GPS navigator whose output formats is IEC 61162 or FURUNO CIF. Data displayable include own ship???s position in lati- tude and longitude (or Loran-C time differ- ences (TDs)), bearing and range to a waypoint selected on the nav aid, own ship???s speed, heading and course, In addition, if a heading sensor or gyrocompass is also con- nected, a line connects a waypoint (selected on navaid), denoted by a dashed ring, with the own ship???s position.

To return the navigation data display on or off, press the [MENU] key and select ???8. NAV DATA???.

To display TDs instead of L/L, press the [GAIN] control. Press the control again to restore L/L.

Occasionally false echoes appear on the screen at positions where there is no target. In some cases the effects can be reduced or eliminated. The operator should familiarize himself or herself with the appearance and effects of these false echoes, so as not to confuse them with echoes from legitimate contacts.

3.1 Multiple Echoes

Multiple echoes occur when a short range, strong echo is received from a ship, bridge,

3.2 Side-lobe Echoes

Every time the scanner rotates, some radia- tion escapes on each side of the beam??? called ???side-lobes.??? If a target exists where it can be detected by the side-lobes as well as the main-lobe, the side-lobe echoes may be represented on both sides of the true echo at the same range, as shown in Figure 4-2. Side-lobes show usually only at short ranges and from strong targets. They can be reduced through careful reduction of the sensitivity or proper adjustment of the A/C SEA.

or breakwater. A second, a third or more ech- oes may be observed on the display at double, triple or other multiples of the actual range of the target as shown in Figure 4-1.

Main-lobe

True echo

Multiple reflection echoes can be reduced and often removed by decreasing the sensi- tivity or properly adjusting the A/C SEA.

True echo

Own ship Multiple

echo

Figure 3-1 Multiple echoes

Side-lobe

Sprious target

Antenna

Figure 3-2 Side-lobe echoes

3.3 Indirect Echoes

Indirect echoes may be returned from either a passing ship or returned from a reflecting surface on your own ship, for example, a stack. In both cases, the echo will return from a legitimate contact to the scanner by the same indirect path. The echo will appear on the same bearing of the reflected surface, but at the same range as the direct echo. Figure 4-3 illustrates the effect of an indirect echo. Indirect echoes may be recognized as fol- lows:

???they usually occur in a shadow sector

???they appear on the bearing of the obstruc- tion but at the range of the legitimate con- tact

???when plotted, their movements are usu- ally abnormal, and

???their shapes may indicate they are not di- rect echoes.

True echo

Bridge

Indirect

Indirectecho echo

Figure 3-3 Indirect echoes

3.4 Blind and Shadow Sectors

Funnels, stacks, masts, or derricks in the path of antenna may reduce the intensity of the radar beam. If the angle subtended at the antenna is more than a few degrees a blind sector may be produced. Within the blind sector small targets at close range may not be detected while larger targets at much greater ranges may be detected. See Figure 4-4.

Figure 3-4 Blind and shadow sectors

3.5SART (Search and Rescue Transponder)

A Search and Rescue Transponder (SART) may be triggered by any X-Band (3 cm) ra- dar within a range of approximately 8 n.miles. Each radar pulse received causes it to trans- mit a response which is swept repetitively across the complete radar frequency band. When interrogated, it first sweeps rapidly (0.4 ??? s) through the band before beginning a rela- tively slow sweep (7.5 ??? s) through the band back to the starting frequency. This process is repeated for a total of twelve complete cycles. At some point in each sweep, the SART frequency will match that of the inter- rogating radar and be within the pass band of the radar receiver. If the SART is within range, the frequency match during each of the 12 slow sweeps will produce a response on the radar display, thus a line of 12 dots equally spaced by about 0.64 nautical miles will be shown.

When the range to the SART is reduced to about 1 nm, the radar display may show also the 12 responses generated during the fast sweeps. These additional dot responses, which also are equally spaced by 0.64 nm, will be interspersed with the original line of 12 dots. They will appear slightly weaker and smaller than the original dots.

Position of

SART

Low speed sweep signal

Sweep start

High speed sweep signal

Figure 3-5 SART display

Showing SART marks on the radar display

To show the SART marks only on the radar display, detune the radar receiver manually. This erases or weakens all normal radar ech- oes, but, the SART marks are not erased be- cause the SART response signal scans over all frequencies in the 9 GHz band. When the radar approaches the SART in operation, the SART marks will enlarge to large arcs, blur- ring a large part of the screen. Reduce the sensitivity and adjust the sea clutter control of the radar.

Summary to detect SART response

1.Use range scale of 6 or 12 nm as the spacing between the SART responses is about 0.6 nm (1125 m) to distinguish the SART.

2.Turn off the automatic clutter suppression.

3.Turn off the Interference Rejector.

General remarks on receiving SART

Radar range scale

When looking for a SART it is preferable to use either the 6 or 12 nautical mile range scale. This is because the total displayed length of the SART response of 12 (or 24) dots may extend approximately 9.5 nautical miles beyond the position of the SART and it is necessary to see a number of response dots to distinguish the SART from other re- sponses.

SART range errors

When responses from only the 12 low fre- quency sweeps are visible (when the SART is at a range greater than about 1 nm), the position at which the first dot is displayed may be as mush as 0.64 nm beyond the true po- sition of the SART. When the range closes so that the fast sweep responses are seen also, the first of these will be no more than 150 meters beyond the true position.

This chapter tells you how to keep your ra- dar in good working order. Before reviewing this chapter please read the safety informa- tion which follows.

DANGER

Turn off the power before performing any maintenance or troubleshooting procedure.

Hazardous voltages can shock, burn or cause death. Only qualified personnel totally famillier with electrical circuits should work inside the units.

RF RADIATION HAZARD

The radar scanner emits high frequency

radio radiation which can be harmful, particularly to your eyes.

Never look directly into the scanner from a distance of less than two feet when the radar is in operation as you could injure the cornea of your eyes. Always make sure the radar is set to stand-by or is turned off before starting work on the scanner unit.

4.1 Preventive Maintenance

Regular maintenance is important for good performance. Always keep the equipment as free as possible from dirt, dust, and water splashes. Make sure all screws securing the components are properly tightened.

A maintenance program should be estab- lished and should at least include the items listed in Table 4-1.

4.2 Replacing the Fuse

The fuse on the rear panel of the display pro- tects the equipment against reverse polarity of ship's mains, overcurrent, and equipment fault. If the fuse blows, find the cause before replacing it. Never use an incorrect fuse - serious damage to the equipment may re- sult and void the warranty.

12V: 10A fuse

24/32V: 5A fuse

CAUTION

Use the proper fuse.

A

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