FIRST EDITION : AUG C : SEP. 4, PUB. No. IME C MODEL1761MARK-3 ( YOSH) All rig hts reserved. Your Local Agent/Dealer

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2 C Your Local Agent/Dealer 9-52, Ashihara-cho, Nishinomiya, Japan Telephone: Telefax: All rig hts reserved. Printed in Japan FIRST EDITION : AUG C : SEP. 4, 2001 ( YOSH) PUB. No. IME C MODEL1761MARK-3

3 SAFETY INSTRUCTIONS Radio Frequency Radiation Hazard WARNING The radar scanner emits electromagnetic radio frequency (RF) energy which can be harmful, particularly to your eyes. Never look directly into the scanner aperture from a close distance while the radar is in operation or expose yourself to the transmitting scanner at a close distance. Distances at which RF radiation levels of 100 and 10 W/m 2 exist are given in the table below. Note: If the scanner unit is installed at a close distance in front of the wheel house, your administration may require halt of transmission within a certain sector of scanner revolution. This is possible Ask your FURUNO representative or dealer to provide this feature. MODEL Radiator type Distance to 100 W/m point Distance to 10 W/m point MK-3 XN10A 0.2 m Worst case 3.0 m i

4 J ß ELECTRICAL SHOCK HAZARD WARNING Do not open the equipment unless totally familiar with electrical circuits and service manual. Only qualified personnel should work inside the equipment. WARNING Be sure that the power supply is compatible with the voltage rating of the equipment. Connection of an incorrect power supply can cause fire or equipment damage. The voltage rating of the equipment appears on the label above the power connector. Wear a safety belt and hard hat when working on the scanner unit. Serious injury or death can result if someone falls from the radar scanner mast. Construct a suitable service platform from which to install the scanner unit. Serious injury or death can result if someone falls from the radar scanner mast. Turn off the power at the mains switchboard before beginning the installation. Fire, electrical shock or serious injury can result if the power is left on or is applied while the equipment is being installed. Do not install the display unit where it may get wet from rain or water splash. Water in the display unit can result in fire, electrical shock or equipment damage. Use only the specified power cable. Fire or equipment damage can result if a different cable is used. CAUTION Ground the equipment to prevent electrical shock and mutual interference. Observe the following compass safe distances to prevent deviation of a magnetic compass: Display unit Scanner unit Standard compass Steering compas 0.50 m 0.40 m 1.00 m 0.80 m HIGH TENSION WARNING DANGER Electrical shock hazard. Do not touch parts in - side this cover. Name: Danger Label Type: Code No.: ii

5 TABLE OF CONTENTS SYSTEM CONFIGURATION... iv EQUIPMENTS LIST... v 1. MOUNTING 1.1 Mounting Methods for Scanner Unit Fixing Holes in Mounting Platform Fastning the Radiator to the Radiator Bracket Mounting the Scanner Unit Display Unit Installation CONNECTIONS 2.1 Connecting the Signal Cable Display Unit Connections Connection of External Equipment Fuse Exchange for 24/32 VDC Power cable Checking the Installation ADJUSTMENTS 3.1 Preparation Sweep Timing Relative Bearing Alignment MAG or GYRO Indication Range Unit Selection Measurement of Blind Shadow Sectors INSTALLATION MATERIALS, ACCESORIES, SPARE PARTS... A-1 OUTLINE DRAWING... D-1 SCHEMATIC DIAGRAM... S-1 iii

6 SYSTEM CONFIGURATION Scanner Unit XN10A-RSB Navigation device Gyrocompass IEC 61162* (In/Out) Gyro Converter AD-100 Display Unit RDP-099 External Alarm Buzzer OP03-21 Intergrated Heading Sensor PG VDC: 10A 24/32 VDC: 5A *Equivalent to NMEA 0183 Rectifier RU-3423 Option 12/24/32 VDC 115/230 VAC iv

7 EQUIPMENT LISTS Standard Supply Name T ype Code No. Qty Scanner Unit X N10A-RSB Display Unit R DP M3 1 Installation Materials CP CP CP CP Select one Accessories FP set Spare Parts SP set Remarks CP , CP , power cable, 10 m signal cable CP , CP , power cable, 15 m signal cable CP , CP , power cable, 20 m signal cable CP , CP , power cable, 30 m signal cable FP , FP FP , Optional Supply Name T ype Code No. External Buzzer OP Rectifier RU Cable Assy. MJ-A6SPF MJ-A6SPF MJ-A6SPF Remarks For navaid, video sounder, 5 m w/6p connector at both ends, cross For navaid, video sounder, 10 m w/6p connector at both ends, cross For AD-100, 10 m w/6p connector at one side Flush Mount Kit OP For display unit Dust Cover For display unit v

8 1. MOUNTING 1.1 Mounting Methods for Scanner Unit The scanner unit is generally installed either on top of the wheelhouse or on the radar mast on a suitable platform. Locate the scanner unit where there is a good allround view. Any obstruction will cause shadow and blind sectors. A mast for instance, with a diameter considerably less than the width of the radiator, will cause only a small blind sector, but a horizontal spreader or crosstrees in the same horizontal plane as the scanner unit would be a much more serious obstruction; you would need to place the scanner unit well above or below it. It is rarely possible to place the scanner unit where a completely clear view in all directions is available. Thus, you should determine the angular width and relative bearing of any shadow sectors for their influence on the radar at the first opportunity after fitting. If you have a radio direction finder on your boat, locate its antenna clear of the scanner unit to prevent interference to the direction finder. A separation of more than two meters is recommended. To lessen the chance of picking up electrical interference, avoid where possible routing the signal cable near other onboard electrical equipment. Also avoid running the cable in parallel with power cables. A magnetic compass will be affected if placed too close to the scanner unit. Observe the following compass safe distances to prevent deviation of a magnetic compass: Standard compass, 1.00 m, Steering compass, 0.75 m. Do not paint the radiator aperture, to ensure proper emission of the radar waves. When this radar is to be installed on larger vessels, consider the following points: The signal cable run between the scanner and the display comes in lengths of 10 m (standard), 15 m, 20 m and 30 m. Whatever length is used it must be unbroken; namely, no splicing allowed. Deposits and fumes from a funnel or other exhaust vent can adversely affect the aerial performance and hot gases may distort the radiator portion. The scanner unit must not be mounted where the temperature is more than 70 C. As shown in the figure below, the scanner unit may be installed on the bridge, on a common mast or on the radar mast. (a) On bridgh (c) Radar mast (b) Common mast Figure 1-1 Scanner unit mounting methods 1.2 Fixing Holes in Mounting Platform Referring to the outline drawing on page D- 1, drill five holes in the mounting platform: four holes of 15 mm diameter for fixing the scanner unit and one hole of mm diameter for the signal cable. 1-1

9 1.3 Fastening the Radiator to the Radiator Bracket For your reference, scanner installation materials list appears in the packing lists at the back of this manual. 1. Remove the radiator cap from the radiator bracket. 2. Coat contacting surface between scanner radiator and radiator bracket with anticorrosive sealant as shown in Figure 1-2. Coat hatched area with anticorrosive sealant. Groove Radiator Figure 1-2 Coating the bottom of scanner radiator for XN10A with anticorrosive sealant 3. Coat threaded holes on the scanner radiator with anticorrosive sealant. 4. Grease the O-ring and set it to the radiator bracket. 5. Lay the scanner radiator on the radiator bracket. 6. Coat the radiator fixing bolts (4 pcs.) with anticorrosive sealant. Fasten the scanner radiator to the radiator bracket with the radiator fixing bolts, flat washers and spring washers. Scanner radiator O-ring Radiator bracket Flat washer Spring washer Hex head bolt (M8 x 30) Coat threaded holes with anticorrosive sealant. Coat bolts with anticorrosive sealant. Figure 1-3 Fastening the radiator bracket to the scanner unit chassis 1.4 Mounting the Scanner Unit The scanner unit can be mounted using the fixing holes on the outside (200 x 200 mm) or inside (140 x 150 mm) the scanner unit. Outside fixing holes Use the hex head bolt ( supplied ) to mount the scanner unit as below. 1. Lay the corrosion-proof rubber mat (supplied) on the mounting platform. Ground terminal Rubber mat Bow mark Figure 1-4 Location of rubber mat 1-2

10 2. Lay the scanner unit on the mounting platform, orienting it as shown in Figure Pass flat washers, spring washers and nuts onto hex bolts. Fasten by tightening nuts. Do not fasten by tightening the hex bolts; seal washers may be damaged. STERN BOW Seal washer Scanner Rubber mat unit Mounting platform Flat washer Silicone sealant Figure 1-7 How to fasten scanner unit to mounting platform Figure 1-5 Scanner unit CAUTION Do not lift the scanner unit by the radiator; lift it by the housing. The radiator may be damaged. 3. Insert four hex bolts and seal washers from the top of the scanner housing. Insert the seal washers with the larger diameter next to the bolt heads. Be sure the seal washer, not other washers, is next to bolt head. Hex bolt Seal washer Flat washer Spring washer Nut Figure 1-6 Fixing the scanner unit chassis 5. Coat flat washers, spring washers, nuts and exposed parts of bolts with anticorrosive sealant. 6. Prepare ground point in mounting platform (within 300 mm of ground terminal on scanner unit) using M6 x 25 bolt, nut and flat washer. 7. Run the ground wire (RW-4747, 370 mm) between the ground terminal and ground point. 8. Coat ground terminal and ground point with silicone sealant as shown in Figure 1-9. Ground terminal Ground wire Silicone sealant GROUND TERMINAL OR Weld here. Hex bolt Flat washer Flat washer Spring washer Hex nut GROUND POINT Hex nut Spring washer Flat washer Hex nut Silicone sealant Ground wire Scanner unit Figure 1-8 How to coat ground point and ground terminal with silicone sealant 1-3

11 Fixing holes inside szcanner unit This method requires removal of the RF unit in the scanner unit to access inside fixing holes. Use hex head bolts, flat washers, spring washers and nuts (local supply) to mount the scanner unit, confirming lengh of bolts. 1. Loose four scanner bolts to open the scanner unit. Refer to Figure 11 for location. Hex head bolt M8X25 SUS 2pcs. Hex head bolt M10X20 SUS 4pcs. Spring Washer M10 SUS 4 pcs. Upper chassis RFunit Cover Square bushing Lower chassis Pan head screw M3X8 4pcs. Figure 10 Scanner unit chassis, upper chassis separated 2. Unplug connector connected between upper and lower chassis. 3. Separate upper chassis from lower chassis by removing two hex head bolts. 4. Remove cover by unfastening four pan head screws. 5. Remove connector from RF unit. 6. Remove RF unit by unfastening four hex head bolts. 7. Lay the corrosion-proof rubber mat (supplied) on the mounting platform. 8. Fasten the lower chassis to the mounting platform with hex head bolts, spring washers, flat washers and nuts (local supply ), and then coat flat washers, nuts and exposed parts of bolts with anticorrosive sealant. Cut a slit in rubber bushing and insert bolt into bushing. Do not use seal washers. 9. Reassemble RF unit, cover and upper chassis. 10. Set four knob caps (supplied) into outside fixing holes. 11. Do steps 6-8 in Outside fixing holes. 1.5 Display Unit Installation Mounting consideration When selecting a mounting location for the display unit keep in mind the following points. Even though the display unit is waterploof, it is recommended that the display unit must be mounted inside an enclosed cabinet. Provide adequate space behind and around the unit to permit circulation of air and to provide convenient access to the rear connectors. Locate the display unit in a position where you can view and operate it conveniently but where there is no danger of salt or fresh water spray or immersion. The orientation of the display unit should be so the radar screen is viewed while the operatior is facing in the direction of the bow. This makes determination of your position much easier. Make sure you allow enough clearance both to get to the connectors behind the unit and to allow you to get your hands in on both sides to loosen or tighten the knob bolts. Make sure you leave at least a foot or so of service loop of cables behind the unit so it can be pulled forward for servicing or easy removal of the connectors. The compass safe distance of 0.5 meters (standard compass) and 0.4 meters (steering compass) should be observed to prevent deviation of the magnetic compass. 1-4

12 Mounting The display unit is mounted in a hanger. The mount itself can be installed either overhead, on a bulkhead, or on a tabletop. The drawing below gives the recommended clearances and mounting dimensions for this unit. You can use the mount itself as a template for locating the mounting screw holes. Although the unit is lightweight (4.8 kilograms), reinforce the mounting place, if necessary. 1. Mark the screw locations by using the hanger as a template. 2. Drill five pilot holes for the hanger. 3. Install the hanger using the screws supplied as the installation materials. 4. Fit the knob bolts and washers to the display unit. 5. Install the display unit in the hanger. Tighten the knob bolts securely. 300 mm (11.79'') 223 mm (8.78'') 232 mm (9.13'') 276 mm (10.87'') WASHER KNOB BOLT MOUNTING HOLES 196 mm (7.72'') 224 mm (8.82'') 80 mm (3.15'') 70 mm (2.76'') 160 mm (6.30'') 80 mm (3.15'') 80 mm (3.15'') Figure 1-9 Display unit, outline drawing 1-5

13 Figure 1-10 Cutting Size for Flush mount Installation of rubber vibration isolators The rubber vibration isorators stabilize the display unit against ship s vibration. Attach them to the mounting bracket if necessary as follows. Align edges of isolator with notches and press in place. Rubber Vibration Isolator (supplied with bracket) Figure 1-11 Rubber Vibration Isorator 1-6

14 2. CONNECTIONS 2.1 Connecting the Signal Cable Only the signal cable runs from the display unit to the scanner unit. In order to minimize the chance of picking up electrical interference, avoid where possible routing the signal cable near other onboard electrical equipment. Also, avoid running the cable in parallel with power cables. Pass the cable through the hole and apply sealing compound around the hole for waterproofing. 1. Open the scanner cover by loosening two screws, and then fix the stay. Plate Gasket Flat washer Bolt 4-M4 16 Figure 2-2 Passing the signal cable through the cable gland assembly 4. Fasten the crimp-on lug on the shield to one of the fixing bolts of the cable gland assembly. 5. Position the signal cable so that no more than 4 cm of the sheath is exposed as shown in the figure below. Tighten fixing bolts on the cable gland assembly. Stay Cable gland Tubing Shield Sheath Within 4 cm Bolt Plate Fixing screw Flat washer CABLE GLAND Gasket Figure 2-1 Scanner unit chassis, cover opened 2. Unfasten the cable gland assembly (plate, gasket, flat washer). 3. Pass the signal cable w/connector through the bottom of the scanner unit chassis. Pass the cable through the gland assembly as shown below. Figure 2-3 How to fix signal cable in cable gland 2-1

15 6. Unfasten four screws shown in the figure below. Four screws 8. Connect the signal cable to the RTB Board (03P9249), referring to the interconnection diagram and the figure below. Note that connector VH2P is not used. J821 VH9P J ß Lead in cable here. J824 NH13P J823 VH4P Figure 2-4 Scanner unit chassis, cover opened Clamp Route cable along here. 7. Pass the signal cable through the cable protector. Cable protector Figure 2-6 Scanner unit chassis, cover opened 9. Fix the signal cable with the cable clamp. 10.Release the stay and close the cover. Loosely fasten the cover fixing screws; you will have to make some adjustments inside after completion of wiring. Figure 2-5 Scanner unit chassis, cover opened 2.2 Display Unit Connections Scanner Unit unfasten to open Fuse 10A (12V) 5A (24/32V) unfasten to open (30m max.) Black White Socket Cap unfasten to open Nav. Receiver NMEA0183 connector Gyro Connector Earth terminal unfasten to open Figure 2-7 Display unit, wiring diagram 2-2

16 Power connection This radar is designed for 12, 24 or 32 volt battery systems. No internal wiring changes are needed for input voltage from 10.2 to 40.0 VDC. A piece of gear of this quality deserves to have a circuit brealer dedicated to it alone. The power cable is fitted with a connector at one end. Pass the other end of the cable through the rubber socket cap (supplied) for waterploofing. Connect the cable to the display unit, then cover the connector with the socket cap. Signal connection Connect the interconnection (multicore) cable from the scanner unit at the back of the display unit. Ground connection Run heavy duty ground wire from the ground terminal at the rear panel of the display unit to the nearest grounding point on the boat. Consult with a qualified e;ectrician if you are uncertain of where the proper grounding points on your vessel are. 2.3 Connection of External Equipment Gyrocompass (or heading sensor) connction If an AC syncro or DC step type gyrocompass is installed on your boat, the true bearing of your ship's heading, of the cursor, and of the EBL (Electronic Bearing Line) may be displayed on the display. You will need the following cable and A-D converter AD-100 (both optionally supplied) to make the connection. To "GYRO" connector on the rear panel Cable Assy 22S m, option Supplied with AD-100 Solder in the field. #1: DATA-H (WHT) #2: DATA-C (BLK) #3: CLK-H (YEL) #4: CLK-C (GRN) Figure 2-8 Gyro connection AD-100 option Follow the steps below to connect the gyrocompass. 1. Remove the connector cap from the GYRO connection location on the rear panel. 2. Solder the end of the Cable Assy to the cable supplied with the A-D Converter. 3. Connect the other end of the Cable Assy to the connector exposed in step Press and hold the [MENU] key for ten seconds to display the INSTALLATION menu. Select 3. MAG/GYRO by the trackball. Then, select GYRO with the [RANGE] key. 5. Presst the [MENU] key again and the indication GYRO appears at the top of the screen. The heading sensor (FLUX-50, C-2000) having AD-10s format or NMEA0183 output data format can be connected instead of a gyrocompass. In this case, you should select MAG instead of GYRO on the INSTAL- LATION menu. When heading data of NMEA0183 format is used, connect the signal to GYRO connector J353#1 (DATA-H) and #2 (DATA-C). The acceptable data (talker/sentence) are **HDM, **HDG and **HDT. 2-3

17 Navigation aid connection If your navigation aid has NMEA0183 or FURUNO CIF data format, your own ship's position in latitude/longitude, the range/bearing to waypoint, ship's speed, heading and course may be input to this radar, and be seen in the bottom text area. You will need the following cable (optionally supplied) to make the connection. Type MJ-A6SPF MJ-A6SPF pin MJ Code no Remarks 5 m 10 m Twisted pair cable 6-pin MJ Figure 2-9 Navigation aid connection 2.5 Checking the Installation After completing the installation, it is a good idea to recheck it to be sure all steps were correctly done. Use the table below to check the installation. The signal cable is securely retained against the mast or mounting platform and is free of interference from running rigging. The cable gland or entry on the deck, if provided, is waterproof. The power connections to the battery are of correct polarity. The plugs at the rear of the display unit are tightly fastened. The fuse F1351 on the rear panel is 10A (12V) or 5A (24V/32VDC). 2.4 Fuse Exchange for 24/32 VDC Power Cable The display unit is supplied with a 10A fuse (F1351) fitted in the fuse holder on the rear panel. This fuse is for use with 12 VDC power supply. For 24VDC or 32 VDC power supplies, please exchange the fuse with the 5A fuse supplied. Use the proper fuse. CAUTION Use of an improper fuse can damage the equipment and void the warranty. 2-4

18 3. ADJUSTMENTS After checking the unit for proper installation its time to adjust it. WARNING Before transmitting the radar make sure no one is near the scanner unit, to prevent the potential risk of being struck by the rotating scanner and exposure to RF radiation hazard. 3.1 Preparation 1. Press the [POWER] key on the display unit, and the front panel will light up. In approximately two minutes and 30 seconds, the message ST-BY will appear at center of the screen. While this warmup is in process, set the [GAIN] control at two o clock, and the [A/C RAIN] and [A/C SEA] controls at fully counterclockwise. 2. When ST-BY appears press the [TX] key. 3. Bring up the [GAIN] control until a small amount of noise appears on the screen. 4. Adjust the [GAIN] control on the front panel, for a little background noise showing on the screen, and then hit the [Range -] key several times to bring you down to the minimum range. Without disturbing the front panel [GAIN] control, adjust the [A/C SEA] control until nearby radar targets are clearly shown on the screen. Too much A/C SEA action will eliminate small targets, and too little A/C SEA action will cause the screen to be so full of targets and noise that it is hard to determine which target is which as compared to visual sightings. Note that adjusting the [GAIN] and [A/C SEA] controls in this manner (GAIN at long range, A/C SEA at short range) will equalize the picture at all ranges, and you will not have to jockey back and forth with the [GAIN] control especially when you change range scale. 3.2 Sweep Timing This adjustment ensures proper radar performance, especially on short ranges. The radar measures the time required for a transmitted echo to travel to the target and return to the source. The received echo appears on the CRT based on this time. Thus, at the instant the transmitter is fired, the Sweep should start from the center of the CRT (sometimes called sweep origin.) A trigger pulse generated in the display unit goes to the scanner unit through the interconnection cable to trigger the transmitter (magnetron). The time taken by the signal to travel up to the scanner unit varies, depending largely on the length of interconnection 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 picture center. The range of objects will also be incorrectly shown. (1) Correct (2) Target pushed inward (3) Target pushed outward Figure 3-1 Examples of Improper and correct Sweep timings 1. Transmit the radar on the shortest range and adjust the [GAIN] and [A/C SEA] controls. 2. Visually select a straight echo (harbor wall, straight pier). 3. Press and hold down the [MENU] key (about 10 seconds) until the INSTALLA- TION menu appears. 3-1

19 Cursor MENU Program No. SEL MENU BY TRKBALL : ITEMS WITH RANGE KEY xx HD ADJ TOTAL ON TIME TMG ADJ : 00 MAG / GYRO TOTAL TX TIME NM / KM : 00 No. of hours radar transmitted No. of hours radar turned on Figure 3-2 INSTALLATION menu 4. With the trackball, select TMG ADJ. MENU SEL MENU BY TRKBALL : ITEMS WITH RANGE KEY HD ADJ DSPL STR TGT TMG ADJ ON SHORT RNG. MAG / GYRO PRESS -/+ KEY NM NM / KM TO STRAIGHTEN. Figure 3-3 Timing adjustment 5. While looking at the target selected at step 2, press the [RANGE +] key if the target is pulled inward, or press the [RANGE -] key if the target is pushed outward. 6. Press the [MENU] key to complete the adjustment. 3.3 Relative Bearing Alignment You have mounted the scanner unit facing straight ahead in the direction of the bow. Therefore, a small but conspicuous target dead ahead visually should appear on the heading mark (Zero degree). In practice, you will probably observe some small error on the display for most installations because of the difficulty in achieving accurate initial positioning of the scanner unit, The following adjustment will compensate for this error. If you don t know how to do it well, it s best you leave this part to a qualified technician. (Remember that the scanner housing fixing bolts remain untightened. They should now be secured if the following alignment is not necessary.) 1. Identify a suitable target (for example, ship or buoy) at a range between 1/8 to 1/4 miles, preferably near the heading mark. To minimize error, keep echoes in the outer half of the picture by changing the range. 2. Measure the bearing to the target by operating the trackball. The bearing is shown at the bottom center of the screen. 3. Using a compass card, visually find the relative bearing to the target. 4. Compare the bearing measured in step 2 and 3 above and calculate the direction and magnitude of the bearing error. If the error is within 30 degrees go to step 9, to correct the error at the display unit. If the error is greater than 30 degrees first make initial adjustments at the scanner unit and then fine tune at the display unit. Heading Mark A Bearing on Radar Target Own ship B Bearing on Chart Figure 3-4 Calculating Bearing Error 5. Press and hold down the [MENU] key (about 10 seconds) until the INSTALLA- TION menu appears. 6. With the trackball, select 1. HD ADJ. The heading marker and tuning range markers appear. See Figure 4-5 (a). 7. Identify a suitable target (for example, ship or buoy) at a range between 1/8 to 1/4 miles, preferably near the heading mark. To minimize error, keep echoes in the outer half of the picture by changing the range. 3-2

20 8. Press a [RANGE] key to bisect the target with the heading marker. See Figure 4-5 (b). 9. Press the [MENU] or select menu by the trackball to complete the adjustment. 10.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. Heading Marker Target Tuning Range Markers Heading Marker (dotted line) Figure 3-5 Display during Heading adjustment 3.4 MAG or GYRO Indication When a gyrocompass or heading sensor is connected to this radar, select it on the IN- STALLATION menu. 1. Select 3. MAG/GYRO on the INSTAL- LATION menu. 2. Select MAG (factory setting) or GYRO with the [RANGE] key. 3. Press the [MENU] key to complete the setting. 3.5 Range Unit Selection The range unit of the cursor and the VRM is selectable for either NM (nautical mile) or KM (kilometer). 1. Select 4. NM/KM on the INSTALLATION menu. 2. Select KM (factory setting) or KM with the [RANGE] key. 3. Press the [MENU] key to complete the setting. 3.6 Measurement of Blind Shadow Sectors In some shadow sectors, it should be remembered that there may not be sufficient intensity to obtain an echo from very small targets even at close range, despite the fact that a large vessel may be detected at a much greater range in non-shadowed sectors. For these reasons the angular width and relative bearing of any shadow sectors should be done during sea trails. In other ships it should be done at the first opportunity after fitting a new radar set. It should be understood that even a small shadow sector can hide another vessel if it is on a collision course. The bearing will remain constant in the shadow area and the approach of the other vessel may remain undetected until it is too late to avoid a dangerous situation. There are two methods of determining the angular width of a shadow sector. 1. Turn the boat very slowly through 360 degrees while a small but clearly defined target is observed at a distance of a mile or so. (Do not use a buoy with a reflector as this target is too powerful to achieve the required result.) 3-3

21 If the echo disappears while the boat is turning, the target has entered a shadow sector and it will again become visible when the target emerges from the shadow. Very quiet considerations of wind and sea are essential to ensure reliable results when this operation is carried out on a small craft since a rough sea can cause a buoy to be lost in the clutter or boat to swing through a shadow sector before the scanner has completed one revolution. In any case an average of several observations of each shadow sector should be taken. It is a waste of time to attempt the operation in anything other than very smooth water with little wind. 2. Another method is to observe the shadow sector against a background of sea clutter. Any shadows will show as dark sectors in the clutter. Note that a shadow cannot be fairly estimated in heavy clutter, as echoes from either side of the sector may be spread into it and give an illusion that objects in the sector are being observed. Nor can it be satisfactorily determined in confined waters, because of the probability of indirect, false or multiple echoes being produced from nearby buildings or other vessels. 0 SCANNER SHADOW SECTOR BLIND SECTOR Figure 3-6 Shadows caused by objects 180 Figure 3-7 Shadow sector diagram 3-4

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