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Antenna 

Mast, 

Reflection 

screen 

I 

Real 

Echo 

, 

, 

, 

..- 

Ghost 

Echo: 

3-5 Virtual 

or 

Ghost Echoes 

Muitiple Echoes 

When there are vertical reflective surfaces at short 

range, for instance, when your ship passes a larger ship, 
the pulsed waves emitted from your radar will bounce back 
and  forth between the two ships (Fig. 3-6). 

As 

a result, 

a few equi-distant echoes may appear in the same bearing 
on the screen.  These echoes are called multiple echoes. 

disappear as your 

moves away or changes bearing 

from the reflecting target. 

3-6 

Multiple Echoes 

Summary of Contents for RA771UA

Page 1: ...SIMRAD MARINE RADAR RA771UA INSTRUCTION MANUAL PIN 855 106335 ...

Page 2: ...INSTRUCTIONMANUAL FOR MAFUNERADAR TYPE RA771UA ANRITSU CORPORATION MAY 92 ...

Page 3: ...s using an i n s u l a t e d conductor DURING MAINTENANCE OF THE SCANNER UNIT THE ANTENNA MUST NOT BE ROTATED Never start maintenance work on t h e scanner unit u n t i l you a r e s u r e t h a t t h e main power s w i t c h on t h e switchboard and t h e power switch on t h e d i s p l a y u n i t are turned o f f and t h e antenna motor line i n t h e scanner u n i t is disconnected of from con...

Page 4: ...r 2 13 Switching t h e Display Modes 2 14 The second EBL and VRM 2 15 The f l o a t i n g f u n c t i o n of the second EBL and VRM 2 16 Setup Modes 2 16 1 E n t e r i n g Setup Mode 2 16 2 Return t o t h e Radar Mode 2 16 3 D e s c r i p t i o n of Each Setup Mode 2 17 Navigation Data Display 2 18 Caution INTERPRETING RADAR PICTURES 3 1 Propagation C h a r a c t e r i s t i c s of Radar Radio Wav...

Page 5: ... S i g n a l s 6 1 5 Allowable S a f e Distance from Magnetic Compass 6 2 S t a n d a r d Equipment 6 3 O p t i o n 6 4 D i p s w i t c h s e l e c t i o n ATTACHED DRAWINGS G e n e r a l System Diagram Scanner U n i t E x t e r n a l V i e w D i s p l a y Unit E x t e r n a l V i e w O u t l i n e Drawing R e c t i f i e r U n i t R e c t i f i e r U n i t E x t e r n a l V i e w I n t e r Connec...

Page 6: ...t t e r Suppression and Auto Gain Control AUTO I n a d d i t i o n t o having conventional s e a c l u t t e r suppression t h i s r a d a r has a newly developed automatic s e a c l u t t e r s u p p r e s s o r has an automatic gain c o n t r o l for e a s y o p e r a t i o n A s a r e s u l t r a d a r video images can be s t o r e d and t h e P i c t u r e r e s o l u t i o n i s e x c e l l e...

Page 7: ...i n g p i c t u r e screen The t r a c k i n g t i m e can be s e l e c t e d from 15 sec 30 s e c 1 min 3 min 6 m i n and continuous An alarm zone s e c t o r can be set by u s i n g VRMl and The t r a c k of t a r g e t p i c t u r e can be d i s p l a y e d on t h e 2 OPERATION 2 1 Key Layout The key and c o n t r o l knob layout i s shown below POWER SWITCH OPERATE KEY RANGE UP KEY GUARD ZONE ...

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Page 9: ...ightness level of echo signals reflected from targets with high reflection coefficients For long range observations increase the gain by turning the control knob clockwise so that slight receiver noise can be observed Receiver noise usually appears on the entire surface of the display as speckled noise Conversely excessive gain at short range will obscure the picture with noise and unwanted echoes...

Page 10: ...he STC c o n t r o l decreases such sea c l u t t e r and makes t a r g e t s e a s i l y v i s i b l e Turn t h e c o n t r o l knob clockwise t o decrease sea c l u t t e r If t h e c o n t r o l knob is turned too far echo s i g n a l from important t a r g e t s may disappear Adjust t h e c o n t r o l very cautiously by observing t h e p i c t u r e with utmost c a r e Usually t h e STC c o n...

Page 11: ... e a This mode i s s i m i l a r t o t h e high STC depends on s e a s t a t e and high GAIN s t a t e i n t h e manual mode n o t e To suppress t h e long range rain snow c l u t t e r u s e t h e manual FTC and or GAIN c o n t r o l with AUTO mode P r e s e t t i n g t h e ATl AT2 l e v e l AT 1 and AT 2 l e v e l can be set by u s i n g f o l l o w i n g procedures 1 S e t t h e AUTO mode t o A...

Page 12: ... mode The i n d i c a t i o n shown below w i l l be d i s p l a y e d and t h e a u t o s e a c l u t t e r suppression mode w i l l remain I n d i c a t e s t h e a u t o STC and manual gain c o n t r o l mode i s s e l e c t e d 3 Automatic Sea C l u t t e r Suppression Manual Gain Control and FTC Control Press t h e FTC key t o add t h e FTC c o n t r o l mode The i n d i c a t i o n shown bel...

Page 13: ...Adjust STC and gain f o r t h e b e s t p i c t u r e counterclockwise t o l e v e l 0 when t h e r e is no r a i n or snow In t h i s s t a t e t h e FTC function is i n e f f e c t i v e Always t u r n t h e c o n t r o l knob a t t h e FTC mode f u l l y 2 5 Measuring Target B e a r i n g s EBL Press t h e EBL key t o select t h e e l e c t r o n i c cursor and t h e indication below w i l l be...

Page 14: ...s t h e ST key The s t r e t c h i n g f u n c t i o n is set and T h i s s t r e t c h i n g f u n c t i o n i s mainly used when echoes Plotting Echo Track from Moving Targets i n d i c a t i o n below w i l l be d i s p l a y e d on t h e t o p r i g h t of t h e s c r e e n P r e s s t h e TRACK key t o p l o t echoes p i c t u r e and t h e TRACK ISSEC The t r a c k of t a r g e t p i c t u r...

Page 15: ...ion i s used when t h e p i c t u r e i n an end of P r e s s the OFF C key The p i c t u r e center w i l l move t o R e j e c t i n g I n t e r f e r e n c e f r o m O t h e r Radars t h i s function r e f e r t o 2 16 3 Setup Modes Selecteble Key 2 1 1 1 What is Radar Interference the same frequency band i s operating n e a r your ship The form of t h e interference p a t t e r n i s not consta...

Page 16: ...gitude and or XTE Cross Track E r r o r i s not displayed on t h e r a d a r s c r e e n 2 1 5 The f l o a t i n g function of t h e second EBL and VRM The f l o a t i n g f u n c t i o n of t h e second EBL and VRM i s usable when t h i s f u n c t i o n is set t o a key a t SETUP mode When t h e f i r s t EBL and VRM are displayed t h e o r i g i n of t h e second EBL and VRM can be moved t o t ...

Page 17: ...t h e range up down keys and a d j u s t w i t h t h e c o n t r o l knob See Figure below DISPLAY PRESET A VRM UNIT B BUZZER VOLUME C PICTURE HOLD D SHF FLASH E PARALLEL CURSOR F NORTH MARK G STC CURVE NORM 3 NM KM SM HIGH LOW OFF OFF ON OFF ON OFF ON OFF ON 3 Note Changing f i g u r e s f o r s e t t i n g l e v e l a r e 0 t o 5 and t h e s m a l l e r f i g u r e shows t h e deeper curve o f S...

Page 18: ...e system calibration will be carried out The calibration will take several minutes iii When the calibration is finished the CALIBRATION COMPLETED is displayed on the screen The auto tunig calibration voltage is displayed at CONTROL area 5 TIMING ADJUSTMENT Before enter the Setup mode set the range scale to This mode is used to adjust the timing for distance Set the det ect ion range to 0 125 or 0 ...

Page 19: ...teering direction 3 Speed Course equipment are fed through the NMEA O183 format VTG the Ship s Speed Course data are displayed automatically on the upper part of the screen When a fluxgate compass or a gyro compass is connected to the radar the compass heading is displayed instead of the course data of navigational equipment 4 Compass Heading are fed through the NMEA O183 format HDM the Ship s Hea...

Page 20: ...v i g a t i o n a l equipment waypoint marks are d i s p l a y e d with a d o t t e d l i n e and a circle When a l o r a n i s used as t h e n a v i g a t i o n a l equipment t h e d o t t e d l i n e i s not d i s p l a y e d on t h e s c r e e n S h i p s heading or course information from a compass 2 1 8 Caution P O W E R FAIL I f RADAR OFF P O W E R FAIL i s d i s p l a y e d on t h e screen ...

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Page 23: ...rably removed from a coastline may at times be displayed on the screen as if they are a coastline Fig 3 3 You must train yourself not to mistake such echoes for coastline Accordingly an echo signal reflected from a high Echoes appear on screen A c t u a l Coastline invisible Visible on Screen I I I I II I Targets Visible on Screen I 2 L Invisible on Screen Fig 3 3 Echo Strength and Incident Angle ...

Page 24: ...g while the ghost appears at a range and bearilrg behind the funnel or the mast Fig 3 4 They are referred A large target at close range may at times appear Direct Reflection Path Reflection Path i Direction of Ghost Echo Heading Marker CRT screen Fig 3 4 Virtual or Ghost Echoes When a target is on the funnel or mast side a series of ghost echoes may appear in the vicinity of a real echo as mention...

Page 25: ... short range for instance when your ship passes a larger ship the pulsed waves emitted from your radar will bounce back and forth between the two ships Fig 3 6 As a result a few equi distant echoes may appear in the same bearing on the screen These echoes are called multiple echoes ihey disappear as your s h i moves away or changes bearing from the reflecting target t Fig 3 6 Multiple Echoes ...

Page 26: ...sed by Side Lobe Beams Echoes Produced by Targets at Lonq Ranges Due to the Duct Phenomenon Depending on the atmospheric conditions a radio wave duct may form above the sea surface In such cases radiowaves can be trapped in the duct travelling in an unusual way over unexpectedly long distances Targets beyond maximum detectable range may appear as echoes on the screen as if they are nearer than the...

Page 27: ...t be turned OFF For more s a f t y maintenance take of fuses on t h e d i s p l a y u n i t A f t e r the POWER SWITCH i s turned OFF high s t a t i c voltage may be retained i n t h e CRT high voltage c i r c u i t and capacitors a r e a p o t e n t i a l hazard t o personnel Discharge high static voltages t o ground by using an insulated conductor before maintenance ocation Procedure Check radia...

Page 28: ...e high s t a t i c voltages t o ground by using an i n s u l a t e d conductor before maintenance I f soot d i r t and d u s t accumulate on densely mounted components unexpected t r o u b l e may r e s u l t Clean u s i n g a vacuum c l e a n e r w i t h a s o f t brush Check a l l connectors f o r poor contact I f p r e s e n t r e p a i r o r replace i t Check a l l f a b r i c a t i o n or mou...

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Page 32: ...izontal plane as the scanner unit radar pulses will be intercepted and it causes to produce a blind angle 3 To avoid formation of a blind angle in the bow direction install the scanner closer to the bow than any blinding obstacle scanner is impracticable because of the ship s structure install the scanner more or less off the keel line or elevate the scanner so that a dip or an angle of declinatio...

Page 33: ...more than 5 as illustrated n I fig 5 6 How to Create a Dip Angle 5 Select a location where the scanner is least 6 Keep the scanner unit as far as possible from the 7 The scanner distance from the display unit should affected by smoke or hot blast from the stack antenna of a direction finder or a VHF transceiver preferably be within the standard length 10 m of multi conductor cable It must never ex...

Page 34: ...the cable f i x i n g p l a t e and rubber 4 Feed t h e inter connection cable through t h e cable i n l e t 5 Fix the rubber and t h e fixing p l a t e w i t h cable s h i e l d terminal 6 Fix t h e transceiver u n i t 7 Connect 10 pin connector t o J1 of MOD PCB and 6 pin connector t o J1 of I F PCB And connect two plugs under t h e transceiver u n i t 8 F i x the cover Take care not t o pinch t...

Page 35: ... e from severe v i b r a t i o n 4 There must be s u f f i c i e n t s e r v i c e clearance a v a i l a b l e around t h e display u n i t 5 The location must be t h e minimum s a f e distance from t h e magnetic compass t o minimize disturbance of t h e compass 2 0m f o r master compass 1 4 m f o r s t e e r i n g compass 5 6 1 Cable Connection 1 Connect t h e scanner cable connector t o t h e b...

Page 36: ...ortest pulse i s s t a b l e then go t o operation i n longer pulse and repeat t h e s i m i l a r s t e p u n t i l t h e operation reaches t o t h e f i n a l pulse condition If t h e magnetron e x h i b i t s unstable operation turn off the high voltage immediately preheat t h e magnetron f o r 5 t o 1 0 minutes and repeat t h e s t e p a l l over again from t h e beginning This w i l l insure ...

Page 37: ...e target echoes A t more t h a n 6 NM range f i n d s e v e r a l weak b u t s t e a d y echoes than 3 seconds t h e range UP DOWN key and p r e s s t h e b r i l l i a n c e key t o e n t e r t o t h e u n d e r l i n e d menu i S e l e c t t h e mode of 2 CALIBRATION by t h e range UP DOWN key and t u r n t h e c o n t r o l knob t o get t h e maximum p i c t u r e v i s i b i l i t y I n t h i ...

Page 38: ... convenience of installation and maintenance Exposed cable must close ly follow surfaces of the ship s structural members or bulkheads and be secured at about 40 cm intervals by approved 5 17 a and b saddles as illustrated in Fig Cable Welded Hanger Band Hoop Buckle spacer a Interior Wall b o o m outside Fig 5 17 Fastening Cable to Bulkhead or Structural Member 5 When a cable runs through a watert...

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Page 42: ...d 100kT 51 4m s With 10m standard cable Power Supply Internal power voltages 10 2 to 41 6 Vdc Power consumption Less than 80 W Separate power supply options 100 110 220 Vac lo 50 60 Hz single phase Power consumption Less than 130 VA 6 1 2 Scanner Unit Antenna Type End fed slotted array Number of revolutions approximately 24 rpm Polarization Horizontal Antenna directivity Horizontal Beam Width 2 5 ...

Page 43: ... 6 6 4 Variable Range Markers VRM Numerical Display Four digits Accuracy Within 1 5 of setting range or SO meters whichever greater Unit NM KM SM selectable VRM2 vRM2 is selectable at SET UP 5 ElectronicBearing Lines EBL mode Steps 0 2 degree steps EBL2 EBL2 is selectable at SET UP mode Display Modes Heading Up HU Following display modes are selectable at SET UP mode Head Set HS North Up NU Course...

Page 44: ...wer supply for external buzzer GLL XTE VTG HDM BWC formats For master compass 4 NMEA 0183 6 1 5 Allowable Safe Distance from Magnetic Compass Display Unit 2 0 m Scanner Unit 2 0 m Display Unit 1 4 m Scanner Unit 1 4 m For steering compass 6 1 6 Dimensions I Antenna 1034 x 180 x 104 3 ft 1346 x 180 x 104 4 ft Scanner Unit 280 x 330 x 355 Display Unit 304 x 255 x 250 6 1 7 Weight kg Antenna 5 3 ft 6...

Page 45: ...048 R 1 0 8 0 R 4 ON ON OFF OFF 3 ON OFF ON OFF RADAR TYPE 2 ON RA771UA lmounting 1 I Manuals I I 3 7 IKey Cap I 16 I I I brushes I I I 6 3 Option 1 AC Power Supply RP113A Input Voltage 100 110 220 Vac 2 AC Power Supply 69 1E A Input Voltage 100 125 3 NMEA Cable 24J138091 with connector 5 m 200 250 Vac 6 4 DIP Switch Selection MAIN PCB s1 6 4 ...

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