RADAR JMA 650 instruction manual

Turn and adjust this control while observing a target on the screen so that the target may be the most clearly displayed.. Adjust this control so that the best pictures may be displayed

CAUTIONS FOR HIGH VOLTAGE

High voltages of hundreds upto thoudands volt are used in radio and radar devices Although

prudent measures for safety have been adopted, sufficient cares should be taken on operation, maintenance and adjustment of the device

Electric shock by thousands volt leads to an instantaneous death for certain, and even electric shock by hundreds volt leads to an instantaneous death occasionally To prevent such an ac- cident, turn off the power source, discharge capacitors by a wire surely earthed at one end, and check that any charge is no longer inside the device, before you put your hand into the inside

It is still better to wear dry wool gloves It is also necessary caution not to use both hands simul- taneously, by putting the left hand into your pocket

The selection of a stable foothold is essential to prevent more extensive or additional injuries When injured by electric shock, disinfect the burn perfectly and give first aid as soon as possible

WHAT TO DO IN CASE OF ELECTRIC SHOCK

When a victim of electric shock is found, turn off the power source and earth the circuit im-

mediately If this is impossible, move the victim away from it without touching him with bare hands as quick as possible He can safely be moved if an insulating material such as dry wood

plate or cloth is used

Breathing may stop if current flows through the respiration center of brain due to electric shock

If the electric shock is not large, breathing can be restored by artificial respiration A victim of electric shock looks pale and his pulse becomes very weak or stops, resulting in unconsciousness and rigidity

FIRST-AID TREATMENTS

As far as the victim of electric shock is not in dangerous condition, artificial respiration should

be started at once at the site Once started it should be continued rythmically

5) Examine the victim’s pulse

c Examine breathing by bringing your face or back of hand close to his face

Keeping the mouth open, stretch the tongue and insert a twel or the like to prevent the tongue from geing drawned (if it is hard to open the mouth with set teeth, open it by a screwdriver and insert a towel.)

IN CASE PULSE CAN BE DETECTED

BUT BREATHING STOPS

(Mouth to mouth artificial respiration) Tilt the victim’s head back as far as his face looks back

(A pillow may be inserted under the neck.)

Pull the jaw into jutting position to open the throat

Pinch the victim’s nostrils shut and place your mouth tightly over his after drawing your

breath long Then blow into mouth strongly Continue blowing at a rate of 10-15 breaths

a minute

Watch carefully and continue artificial respiration till natural respiration is resotred

If the opening of mouth is difficult, insert a vinyl pipe or the like into a nostril and blow into it by shutting the other nostril and mouth perfectly

Victim may stand up suddenly when he becomes aware He should lie quietly and kept

warm and calm

Serve him with hot coffee or tea (but never alcoholic drinks)

Method of Mouth to Mouth

artificial rospiration

Tilting Bake of Victim’s Head

Put one of your hands on the victim’s fore-

head and the other under the neck (1) In

general his mouth opens when the head is

tilted back, making easy mouth to mouth

artificial respiration

Place your mouth tightly over his and press

your cheek against his nose @ or pinch his

nostrils by your fingers @® to prevent air

leakage

Blowing into Lungs

Blow into the mouth till the chest rises The first 10 breaths should be performed as fast as possible

Therefore, artificial respiration should be started at once

Put the heel of one hand over the lower 1/3 of his breastbone and the other hand on the

back of the first Apply your weight so that the brastbone is compressed by about 2 cm

(Repeat it at a rate of about 50 times a minute.)

(Cardiac massage)

In case of one rescuer

After about 15 times cardiac massages, give mouth to mouth artificial respiration 2 times,

and repeat them in this manner

In case of two rescuers

While the victim is massaged, another person should give mouth to mouth artificial respira- tion A breath is interposed after 5 cardiac massages

(Cardiac massage and mouth to mouth artificial respiration)

Examine the pupils and pulse often When they become normal stop the first aid treatments, serve the victim with coffee or tea and keep him warm and calm, while watching him carefully

Commit the victim to a medical specialist, according to the situation For earlier recovery

of the victim from the mental shock, the understanding of bystanders is essential

CONTENTS

SECTION 1 GENERAL DESCRIPTION 1-1

1.1 INTRODUCTION_ c 1-2 1.2 SPECIFICATIONS 2.1 cece cere tence nee teens 1-3

SECTION 2 OPERATION OQ Q Q Q Q HH khe 2-1

2.1 OPERATION 0.2 cee cece eee tence tenn eenneeee 2-2 2.2 HOW TO USE THE KNOBS_ 2-10 2.3 HOW TO READ THE CONTROLS 2-11

24 PLOTTER On HH nh HH ke ka 2-16

25 MEASUREMENTS cc 2-17 2.6 HOW TO USE OPTIONAL ASSEMBLES 2-26

SECTION 3 MAINTENANCE_ che 3—1

3.1 GENERAL Ống nh he kh nh 3-2 3.2 MAINTENANCE OF EACH UNIT 3-3

SECTION 4 TROUBLESHOOTING cà 4-1

41 GENERAL 0 cece cc eee enn teen kh ke 4-2 4.2 OPERATION CHECK_ c 4-3 4.3 FAULT FINDING cee cece tee e eee tenets 4-4

44 TROUBLESHOOTING_ - 4-5

45 REPLACEMENT OF MAJOR PARTS 4-7

46 ADJUSTMENTS_ -.QQ HQ nh ha 4-9 SECTION 5 PARTS LIST Q QQ QQ HH nh HH kh 5-1

INTERCONNECTION DIAGRAM OF JMA-650-7 RADAR INTERCONNECTION DIAGRAM OF JMA-650-9 RADAR POWER SUPPLY DIAGRAM OF JMA-650-7 RADAR POWER SUPPLY DIAGRAM OF JMA-650-9 RADAR INTERNAL CONNECTIONS OF NKE-189 SCANNER UNIT INTERNAL CONNECTIONS OF NKE-189/189D SCANNER UNIT (WITH BUFFER CIR.)

INTERNAL CONNECTIONS OF NKE-190F/190DF SCANNER UNIT INTERNAL CONNECTIONS OF NTG-250 TRANSMITTER-RECEIVER UNIT INTERNAL CONNECTIONS OF NCD-753 DISPLAY UNIT

INTERNAL CABLE CONNECTIONS OF NCD-753 DISPLAY UNIT INTERNAL CONNECTIONS OF NSK

CIRCUIT DIAGRAM OF TERMINAL BOARD (PC409) CIRCUIT DIAGRAM OF POWER UNIT

SECTION 1 GENERAL DESCRIPTION

†1.1 INTRODUCTION

The JRC Model and are ideal radars designed to be high brightness

especially short-range, high performance, high quality and high reliability JMA-650-7 and JMA-650-9 are provided with 7ft and 9ft slot scanner unit respectively The transmitting output power is 50kW A 12-inch cathod ray tube is included in the display unit These

radars have been semi-conductorized (excepting a special electron tube), so increased reliability have been expected

These radars are designed to meet IMCO performance standards (A-222) which are in

accordance with the provision of SOLAS

The composition of the radar depending on the ship’s mains are shown in Table 1.1

TABLE 1.1 COMPOSITION OF THE RADAR AND SHIP’S MAINS

hip’s Main AC 100/110/115V | AC 100/110/115V

50/60Hz 1¢ | 50/60Hz 3¢

Less than 1°

Relative bearing and true bearing

—25 to +55°C (up to +70° under the left condition)

Other Units except the scanner unit;

—15 to +55°C

All units 95% at +35°C

Amplitude from Oto 500 cpm with an excursion of 3 mm

from 500 to 1500 cpm with an excursion of 0.75 mm

from 1500 to 3000 cpm with an excursion of 0.2 mm

Power input voltage allowance Power input voltage + 10%

(with the maximum cable

Height 625 mm

Swing circle 2810 mm (9 feet) Approx 46 kg (7 feet)

Approx 77 kg (9 feet) Horizontal

1° (7 feet) 0.8° (9 feet) 20°

Less than — 26 dB (within + 10° of Main Beam) Less than — 32 dB (Out side + 10° of Main Beam)

1-3

At low speed of 9 feet

6) Scanner drive motorinput: AC 100/110/115 V, 50/60 Hz, 1¢ 400 VA (7 feet)

4) Transmitting frequency: 9375 +30 MHz 5) Transmitter output

By changing the switch position of

from đồi đồ , the following pulse width and

repetition frequency can be selected

0.7 ws/1000 Hz (3n.m.) 1.0 ys/750Hz (6,12 n.m.)

12) IF amplifier: Center frequency 60 MHz

Band width 17/3 MHz Gain more than 90 dB

1.2.4 Display Unit NCD-753

1) Dimensions: Width 655 mm

Depth 517mm Height 1028 mm 2) Mounting: Selfstanding type, drip-proof structure

1-4

0.05, 0.1, 0.25, 0.25, 0.5, 1,2, 4, 8, 20 n.m

Less than 1.5% of the maximum range of the scale in use or 70 m, whichever is greater

00.01 to 120.0 n.m 4-digits digital read out

Fixed deflection coil, resolver system

Manual

360° scale graduated at intervals of 1°

2/3 tube radius (max range 120 n.m.) Reflection plotter

Electronic flash line °

POWER Switch OFF-STAND BY-ON (_)- RANGE (2 (0.25, 0.5, 0.75, 1.5, 3, 6, 12, 24, 48, 120)

TUNING -~“

GAIN «#*

CONTRAST ANTI-CLUTTER SEA

ANTICLUTTER RAIN RANGE RINGS BRILLIANCE O@m

SWEEP BRILLIANCE VRM BRILLIANCE © VRM DOWN-UP_ _(@)—@©) TF-SI PULSE WIDTH

CENTER «+ -

SHM BRILLIANCE SHM

INTRF REJECT

PANEL PLOTTER DIAL ( )~€&) NORTH UP-HEAD UP @&® -() EBL MODE (OFF-CENTERED 1“

CENTERED 2 — IND 1 - IND 2) EBL BRILLIANCE

EBL MARKER INTERVAL (DOWN-UP) EBL MARKER BRILLIANCE

EBL BEARING EBL ORIGIN JOYSTICK

1.2.5 Optional Assembles

1) Second Variable Range Marker Unit

2) C.F.A.R Unit

3) Log Amp Receiver with AFC

4) True Motion Unit

5) De-icing Scanner Unit

6) Performance monitor

7) Inter Switching Unit

8) Sub Display Unit

1.2.6 Cable Length Allowance between Units

Scanner to Display

Scanner to Transmitter-Receiver

Display to Transmitter-Receiver

NNX-3 NNB-52 NAF-34 NCZ-689 NKE-189D (7 ft.) NKE-190DF (9 ft.) NJU-13

NQE-414/NQE-448

EX JAS-800

Maximum Length 50m

30m 20m

0" NON PAMỚ ĐNG, SUSSGE

Fig 1.4

DISPLAY UNIT NCD-753

SECTION 2 OPERATION

2.1 OPERATION

2.1.1 Layout of Controls

2.1.2 Function of Controls

2.2 HOW TO USE THE CONTROLS

2.3 HOW TO READ THE SCREEN

2.4 PLOTTER

2.5 MEASUREMENTS

2.5.1 Range Measurement

2.5.2 Bearing Measurement

2.5.3 Measurements of CPA and TCPA

2.5.4 Measurement of the Course and the Speed of the Targets

2.5.6 Correction of the Course and the Speed

2.6 HOW TO USE OPTIONAL ASSEMBLES

2.1 OPERATION

Since all controls are located on the front panel of the display unit, the navigator can

operate this Radar very easily In order to get an optimum radar display, it is necessary for

2.1.1 Layout of Controls

The layout of controls is shown in Fig 2.1

@?DISPLAY section

.@ [EBL MARKER INTERVAL DOWN-UP

@3 [EBL MARKER BRILLIANCE

® (NORTH UP-HEAD WP] )-©)

At the [OFF] QO position, there is no power supplied to the display unit, trans-

mitter-receiver unit and scanner unit The radar, therefore, can not operate Note: Take notice of the voltage which presents at the input terminal TB201 of the trans- mitter-receiver unit even if OFF © position

At the |STAND BY C) position, the input power relay in the Transmitter- receiver unit is energized, the power is supplied to the display unit, transmitter- receiver unit and scanner unit from the power unit In this condition, all circuits are energized except the CRT high voltage power supply circuit in the display unit,

the modulating circuit in the transmitter-receiver unit and the scanner driving

motor In approximately 3 minutes after switch to [STAND BY|C › the[READY]

lamp on the front panel of the display unit will light up and the Radar is ready for operating condition The Radar can be operate in use whenever required,

if the lamp lights up This 3 minutes are required to heat up the heater

of the magnetron

At [oN(+) position, the Radar is allowed to proceed in its normal operating con-

dition The scanner starts in rotation and target echoes are received, then ampli-

fied and displayed on the screen

Even though the switch is set to @) before the lamp lights up,

the radar transmitting pulse will not be transmitted and any echoes will not be displayed on the screen

When performing the radar observation at the short intervals, by keeping the

switch set to |STAND BY C) and setting the switch to ©) only when

observing, the long life of the navigation can be assured

At the [STAND BY C) position, the tuning indicator in the display unit does

not light up

This switch selects the range which you want the radar to cover The selected range automatically determines the pulse repetition frequency, pulse width, the band width of the receiver, the band width of the video amplifier and the range rings

The selected range scale is shown by glowing figures The range scale and the range rings interval are displayed on the display section

For JMA-650-9, the rotation speed of the scanner unit automatically changes

At positions less than 3 n.m., the rotation speed is approx 26 rpm (60 Hz) and at positions more than 6 n.m., it is approx 17 rpm (60 Hz)

Relations of range scale to range rings, pulse repetition frequency, pulse width,

and band width of receiver are shown below

24

interval rings frequency width of receiver

0.25 n.m 0.05 n.m 5 3000 Hz 0.08 us 17 MHz

05 7 01 7 5 3000 ” 0.08” 17 7

075 7 0.25 7 3 3000 ” 0.08” 17” 15.” 0.25 7 6 3000 ” 0.08” 17 7”

By this control, the varactor voltage of the gunn oscillator (A301) of the receiver

can be changed, so its oscillating frequency can be changed

Turn and adjust this control while observing a target on the screen so that the target may be the most clearly displayed When there is no target available for the said observation, adjust the control so that the light emitting diode (LED) of the tuning

display ™\on the display section may be the brightest This is the tuning point It

is easy to tune, if tuning is performed in the position of 3 to 120 n.m

5)

25

By turning this control clockwise, the gain of the receiver increases and the ob-

serving range of the target expands Adjust this control so that the best pictures may be displayed on the screen, according to the range scale in use In the short range, it is advisable to operate the equipment with this [GAIN] control set at a setting where the receiver gain is rather lowered a little In the long range, it is advisable to operate the

equipment with this[GAIN] control set at a setting where the receiver gain is rather

increased a little

CONTRAST

The brightness of the whole screen can be adjusted without changing the condi-

tion of the echoes, such as small targets, etc on the screen, by changing the voltage of

the video amp by means of this control

Perform the adjustment by using this control with[GAIN] so that the best

picture may be obtained

6) [ANTICLUTTER SEA] 3-€

This control reduce the gain level for short range to suppress the strength of the sea clutter If there is no sea clutter around the own ship when the sea is calm, keep this control set fully counterclockwise As turning this control counterclockwise, the bright part appearing at around the center due to the sea clutter gradually disappear

Be sure not to eliminate the necessary target by turning this more than necessary

?.[ANTICTUTTERRAIN) (3C)

This control changes electrically characteristic of the video amplifier circuit in the display unit When fully counterclockwise, the video signal is connected to the

amplifying circuit as it is As the control is turned clockwise, the narrow video signal

is connected to the amplifying circuit When fully clockwise, the observed length of

the target on the screen reduces and the disturbance on the screen due to the rain and snow clutter can be eliminated But be sure not to miss the small target

This control is used to adjust the brightness of the fixed range rings Adjust this

control so that the range ring may be the most easily read according to the range in

use

9) (SWEEP BRILLIANCE]

This control is used to adjust the brightness of the screen Adjust this control so

as to obtain the best screen according to the range scale in use

10) [VRM BRILLIANCE] (_)~@)

This control is used to adjust the brightness of the variable range marker Adjust

this control to obtain the best brightness of the variable range marker to be read ac-

cording to the range s-ale in use

11) [VRM ĐOWN-UP] @)-—©)

This is the switch to shift position of VRM The range increases by pushing the switch and the range decreases by pushing the © switch The shifting speed is determined by and switches, that is, [F] switch is fast movement and [S]switch

target and then by the S| switch, match the marker on the echo

The range of the variable range marker is displayed by the digital display LED on the display section The display is done by the 4-digit figures The measurement can be done at intervals of 0.01 n.m on the scale range from 0.25 to 48 n.m and at the intervals of 0.1 n.m on the scale range of 120 n.m If the observed distance exceeds the maximum measuring range scale, the displayed figure returns to 00.01 or 000.0

I2[E0LsE wipim]@ ~Œ

This function is carried out on the range from 3 to 120 n.m Usually, this switch is used at the @ position (see item 2) If the is selected, the transmitting pulse width increases from 0.2 us to 0.7 us at the range of 3 n.m At the range of 6 and 12 n.m., the width changes from 0.7 us to 1.0 us This switch changes video band width also, so at the range of 3 to 120 n.m If the đồ 1s selected, viđeo band

width of Video Filter is 300 kHz The sensitivity is improved by these and the small

target (buoy, small ship, etc.) becomes larger and can be easily to see

26

13) [CENTER] $

The two shift control ( ‡ vertical and qm horizontal) are provided for shifting

the center of thePPI sweep (own ship) within the range of two-thirds effective radius of

‘the screen in order to observe the arbitrary direction extending over broad range

At this time, the range scale is extended as follows

This control is used to adjust the brightness of the ship’s heading marker (SHM)

to show the course direction of the own ship Adjust this control so that SHM becomes

brighter By turning it counterclockwise, SHM becomes darker, but SHM will never

disappear

15)

This ship’s heading marker (SHM) to show the course direction of the own ship

is always displayed on the screen While this switch is being pressed, SHM disappears It

is, therefore, easy to confirm the small target in the bow direction By releasing the

switch, the SHM is automatically displayed again

16) [INTRF REJECT]

The switch is attached to this control When there is no interference from other radars, set this switch to OFF If there are any radar interference, adjust by turning

this control so that the radar interference may be maximumly eliminated

1) ENED O-B This is the control adjust the illumination of letters and symbols of controls on

the panel It is convenient for the night operation to set it to the proper brightness

This is the control to adjust the plotter illumination and the brightness of the

bearing scale Adjust the brightness so that the plotted mark and scales may be read easily on the screen When fully counterclockwise, the bearing observation can’t be performed Take notice of this fact

2-7

19) [NORTH UP-HEAD UP @® - ©

20)

21)

22)

By setting this switch to @® , the zero degree of the bearing scale

is always due north and such a screen where SHM always indicates the bearing of the

own ship course, is obtained Even though the own ship’s course changes, only bearing

of SHM will change, and the bearing of the fixed targets will not change In such a

condition, the bearing of the measured target is true bearing At this time, make sure to

set the switch of the north stabilizing kit to ON

At the @) position, the zero degree of the bearing scale always

coincides with the SHM (the own ship’s course) Even if the course of the own ship changes, the SHM will not change from zero degree, but the bearing of the fixed

target will change In such a case, the bearing of the measured target is relative bearing

to the course of the own ship

This EBL (electronic bearing line — electronic cursor) switch provides means of

the navigator to select the EBL depending on its use

At the position, EBL does not appear on the screen

At the eee position, one EBL is displayed The origin of the EBL is

the same as the center of the PPI sweep When measuring the bearing of the target, by placing EBL on the target by means of EBL BEARING , the bearing can be read out from the bearing scale

At the position, two EBLs appear on the screen One is the same

as position as above and the other is the center of the bearing scale

In case the PPI sweep is placed out of the center by [CENTER| IW , it is difficult to measure the bearing of the target at the position But at the position, the bearing, matched to the target by EBL BEARING, can be read out easily by EBL coming out from the center of the bearing scale

At the position, one EBL is displayed The origin of EBL can be shifted

according to the EBL ORIGIN JOYSTICK lever

At the position, two EBLs are displayed One of the origin of EBL is the

center of the bearing scale and the other can be shifted according to the EBL ORIGIN JOYSTICK lever This using method is almost the same as that of |IND 1] Moreover, the information on the bearing can be obtained

EBL BRILLIANCE

This control is used to adjust the brightness of EBL As turning this clockwise, the

brightness increases Adjust this control so that EBL may be read easily

[EBL MARKER INTERVAL DOWN-UP

This switch is used to vary the intervals of markers on EBL While pressing the switch, intervals become shorter, while pressing the [UP switch, they become

longer It is convenient to use this switch as required, when obtaining the information

23) | EBL MARKER BRILLIANCE

This is the control to adjust the brightness of the EBL marker Adjust this control

so as to obtain EBL markers most adequate to observe

24) EBL ORIGIN JOYSTICK

When the switch is set to or , the origin of EBL can

be shifted according to this lever (within the limit of two-thirds radius of the effective radius)

25) EBL BEARING

This is the control to adjust the bearing of EBL It is very convenient to use this

lever when measuring the bearing of the target by using EBL

27) RANGE of VRM Marker

2.1.3 Operating Procedure (Starting — Observation — Stop)

After knowing the layout and functions of controls on the front panel proceed as follows

— Starting —

2) Ifthe lamp lights up after about 3 minutes, set Cto [ON] @)

3) Set[RANGE |to “48” or “120”

4) Adjust by turning it clockwise or counterclockwise so that the target may

be displayed the most clearly on the screen In case there is not proper target on the

most brightly Now it is ready for observation

5) Set [RANGE] (4) to the appropriate position for a desired range

€)-€@ and [ANTL-CLUTTER RAIN

and obtain the necessary information of collision avoidance

— Stop —

Set the power Switch to OC

2.2 HOW TO USE THE CONTROLS

When measuring the position of the target on the radar screen, the best picture on the

screen allow the accurate measurement

Controls to get the best picture on the screen is as follows

[TUNING] = [GAIN] = [ANTI-CLUTTER SEA] QS

Before operating these adjusting controls, the navigator should understand functions of

these controls described in 2.1.2 The following describes the points to which attention

should be paid when adjusting these controls

1) |TUNING | ^>

Whether tuning is obtained or not can be confirmed by means of the test meter

Adjust this control so that the clearest picture may be presented on the screen

If the best tuning condition is not obtained, especially the target at the long

range and the small target even at the short range may be missed Since the oscillation frequency of the magnetron is stabilized about 10 minutes after the POWER switch set

to @) , it is better to perform the readjustment 10 minutes after the first

adjustment

» GAR] A

With too little gain, the small targets are missed and there is a decrease in the de- tected range With excessive gain, since the screen becomes brighter because the noise increases, the contrast between echoes and background noise reduces, making target

observation more difficult In the crowded regions, the gain may be reduced to clear

the picture This must be done with care since important target may be missed

3) [ANTLCLUTTER SEA) C>~€

The bright section on the sea due to the sea clutter gradually disappears as the

is turned clockwise But with the excessive ;|ANTI-CLUTTER

SEA] , the necessary target may disappear, too So, be careful The targets such as

buoy, small craft, etc as can be observed only in the calm sea and in the short range may disappear very often in case of the strong sea clutter together with the sea clutter

as increasing | ANTI-CLUTTER SEA]

4) [ANTECLUTTER RAIN

The FANTLCLUTTER RAIN | enables to discriminate adjacent targets from the rain or snow clutter In the heavy rain or snow which may clutter the screen, this con- trol allows to give clear echo from the target Also, this control can reduce the sea

clutter Therefore, use of both [ANTI-CLUTTER SEA] and [ANTI-CLUTTER RAIN]

will help to make the picture clear But with the excessive ANTI-CLUTTER RAIN],

the small target and the targets at the long range may be difficult to be seen and may

disappear Take notice of this fact Usually, set this control fully counterclockwise

2-10

2.3

2-11

HOW TO READ THE SCREEN

What is demanded for a user of the radar is how he observes and interprets a radar

screen to get the best aid for the navigation He should observe the screen, understanding

the advantage and disadvantage of the radar It is important to enhance his experience for reading the screen, by comparing the echoes on the screen of the radar with the target seen

with naked eyes at the fine weather

The radar allows to monitor the courses of the own ship and other ships in an open sea,

to confirm the navigation marks such as buoys as the ship approaches the port, measure the

position of the own ship on the chart based on the range and the bearing of the land, is-

lands, etc in the adjacent seas and to know the position and the movement of the heavy rain that appears on the screen Items associated with the screen of the radar are described below

The radar waves have such a characteristic that they propagate along the curvature

of the earth This characteristic changes depending on the nature of the layer of the air

in the space through which the radar waves propagate Under the normal propagating condition, the distance to the radar horizon (D) is found to be about 10% longer than

that to the optical horizon D is described with the following formula

D = 2.23 @/hl + Vh2) (n.m.)

where hl: the radar scanner height measured above the sea level (m)

h2: the height of a target measured above the sea level (m)

Fig 2.2 shows the figure to obtain the maximum detected range of the target,

which is limited by the curvature of the earth under the normal propagation

Fig 2.2 RADAR HORIZON

2-12

2-13

2)

3)

4

For example, assume the height of the scanner unit of the own ship is 10 m

(1) The height of the target which can be observed on the radar screen at the detected

range, 64 n.m should be more than 660 m

(2) When the height of the target is 10m, the detected range is approx 15n.m But the maximum detected range of the target, which can be observed on the radar

screen, changes due to the size of the target, weather condition, etc and there may be cases where it may lengthen or shorten

Echo strength

The strength of echoes returned by the target depends on not only the size and height of the target but also material forming the target and the configuration of the target Therefore, it is not always true that the echoes returned by the higher and larger target provides an echo having a larger strength

Especially, the coast line is affected depending on the topographic conditions When the coast is greatly sloping, since the mountain on the land appears as the echo

on the screen as shown in Fig 2.3 The special cares are required to measure the dis-

tance to the coastline

Mountain which appears

of the echo on the screen changes due to the direction of the wind

A tide-eddy may appear at the gently sloping line resembling to the coast line

(1) Shadow

There may be a case where any target existing in the same đirection as a funnel

or mast placed near the scanner unit fails to appear as a target on the screen This

is because that the radar transmitting pulse reflects by said funnel or mast due to the location of the scanner unit The existence of the above-mentioned trouble can be confirmed by observing the sea clutter and checking for any faint or blank shade If those shadows exist, since it would always appear in a given direction,

the observer must memorize that direction

(2) Sidelobes

It sometimes happens that the echoes resulted from the sidelobe of the radiation beam from the scanner unit appears as the broken arc line at the same distance as

the echo of the target It is comparatively easy to identify such kind of the false

echo when the target stands alone (See Fig 2.4.)

Fig 24 SIDELOBES

(3) Secondary echo

Two echoes may be displayed on the screen for one target at the short range: One directly reflected by the target and the other secondarily reflected by the mast or funnel In this case, the secondary echoes appear in the direction of the mast or funnel (See Fig 2.5)

DIRECT PROPAGATION PATH

OF RADAR PULSE

REAL ECHO

RADAR SCANNER

FALSE ECHO DUE

SECONDARY REFLECTED

R P FUNNEL ADAR PULSE

Fig 25 SECONDARY ECHO

2-14

2-15

(4)

(5)

(6)

Multiple false echoes

It sometimes happens that a building or a large vessel with a large vertical surface

may produce multiple false echoes due to the multiple reflections of radar pulses

These echoes are a series of equally spaced echoes on the same bearing In such a case, the nearest echo to the radar is the real echo presented by the target

For example, supposing that the scale range is 6 n.m (repetition-frequency is

1000 Hz), the first pulse reflects from the target more than 81 n.m away, and it

is received during the next pulse repetition time The false echo is produced at the place whose range is reduced by approx 81 n.m from the actual range

Supposing that the false echo is produced at the position of 5 n.m on the screen, the actual range of this target is 5 + 81 = 86 n.m Also when the scale range is

1.5 n.m (repetition frequency is 3000 Hz), the false echoes may be produced at the position whose range is reduced by 27 n.m from the actual range

This kind of false echoes can be judged by the fact that the range of the echo is

changed by changing the scale range (and changing the repetition frequency)

Radar interference

Radar interference is liable to occur in the vicinity of another shipborne radar

using the same frequency band These interferences normally take the form ofa large number of bright dots scattered over the whole screen These can be easily distinguished from normal echoes by such a fact that always they do not appear

in the same place (See Fig 2.7.)

Fig 27 RADAR INTERFERENCE

2.4 PLOTTER

The plotter is the equipment to record the position of the target displayed on CRT on the plotter surface The general principle of a plotter is shown in Fig 2.8 Use the supplied

plotter crayon or the fine wax pencil in the market to plot the target on the plotter surface

S1 Use the cotton or soft cloth to erase the plotted records

Letters on Si illuminated by [PLOTTER DIAL|(_ )-@) reflect on Glass $2 and the

light from the target on the screen passes through Glass $2 Wherever observer’s eyes posi-

tion, there is little parallax and the observer can plot the target on the plotter surface S1, as

if he wrote directly on CRT with crayon The record plotted by crayon shines brilliantly and indicate the target

‘EYE PLOTTER CRAYON X7 EYE

T

TARGET CRT SURFACE

Fig 2.8 PLOTTER

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2.5

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MEASUREMENTS

On CRT of the display unit of the radar, the own ship (more accurately, the position

of the scanner unit) is at the center of the screen (origin of the co-ordinates) and other targets are presented in polar coordinates (the picture is called as PPI) Therefore, the picture on the screen shows a plan view of the position of the targets around the own ship and the targets are displayed as the brilliant echoes By using EBLs which are the feature of

this radar, the following measurements can be performed on the screen

1) Range measurement between the own ship and the target (See (1) in 2.5.1.)

4) Measurements of CPA and TCPA (See 2.5.3.)

6) Deciding the new course or speed for collision

7) Correction of the course and the speed (See 2.5.6.)

When performing measurements described in 5) and 6), the speed of the target ship and

the passing range of the own ship during the observation should be obtained based on the

passing range of the target during the observation In such a case, the speed table shown in Table 2.1 is very helpful and convenient

Time (minutes)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

NM |.1 15} 2 | 25 35} 4 | 45) 5 | 55) 6] 65) 7 | 75

/ /

TABLE 2.1 CONVERSION TABLE FOR SHIP'S SPEED AND TIME

25.1 Range Measurement

1) Range measurement between the own ship and the target

For the range measurement of the target, check the echo of the target on the screen, and setting | EBL MODE| to |CENTERED 1] , turn EBL BEARING so that EBL may come on the target By pressing |VRM DOWN-UP @-@ , place the

variable range marker (VRM) on EBL on the point corresponding to the target Read

the indication of the VRM indicator on the display section These indicated figures

show the range (n.m.) from the own ship to the target (See Fig 2.9.)

03 - 50

——- — BRILLIANGE EBL CENTERED 2 EBL MODE

CENTERED 1 INDI OFF - ~ IND2 EBL

marker ring from the inner ring or from the outer ring

Set [EBL MODE |to | IND 1| By moving EBL ORIGIN JOYSTICK to and fro in

all directions, bring the origin of EBL on either of two arbitrary points By turning EBL BEARING , place EBL on the other point By pushing | VRM DOWN-UP _@ switch, place VRM placed on EBL on that point The range between two points can be read out on the VRM indicator (See Fig 2.10.)

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There are two bearings as the bearing of the target, one is relative bearing and the other

is true bearing Measure the bearing by setting [NORTH UP-HEAD UP Oa to

NORTH UP @® or [HEAD UP @®

The relative bearing is the bearing in which the course direction of the own ship

is set to 0° Set [NORTH UP-HEAD UP] to [HEAD UP] When the origin of the PPI

sweep is at the center of the screen, set EBL MODE to Place EBL

on the center of the target by turning EBL BEARING and read the bearing of the target on the bearing scale

When the origin of the PPI sweep is not at the center, that is, off-center, set [EBL MODE] to Place EBL coming from the PPI origin on the center of the target, by turning EBL BEARING At this time, read the bearing scale indicated

by the other EBL coming from the center (See Fig 2.11.)

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EBL EBL MODE

CENTERED 2 BRILLIANCE CENTERED 1, 1 NDT

True bearing is the bearing in which the due north of the earth is standardized, by

setting [NORTH UP-HEAD UP]to| NORTH UP|

The upper part on the screen of the display“Unit, that is, 0° of the bearing scale indicates the due north After setting [NORTH UP-HEAD UP | switch to [NORTH UP

i

©) , read the bearing scale with the same way as described for the measurement of the relative bearing This read bearing describes the true bearing of the target (See Fig 2.12.)

compass coincides with the true bearing indicated by the radar If not, perform meas- urements after doing the adjustment according to the Clause 4.6.3

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EBL MODE

EBL

BRILLIANCE CENTERED 2

OF TARGET “1 F~0° I§ TRUE NORTH \ INDI

OWN SHIP’S POSITION

EBL

BEARING

FIG 2.12 TRUE BEARING MEASUREMENT

2-5-3.Measurements of CPA and TCPA

It is the basic and general problem on the sea during the navigation to obtain the

relative movement of other ships to the own ship, its CPA (closest point of approach) and TCPA (time to CPA concerning the ship approaching to the own ship) The information

of collision avoidance can be easily obtained by using inter-scan system EBL and EBL

markers which are features of this radar (See Fig 2.13)

this time, write its time, too

and VRM by using [EBL BRILLIANCE] , [EBL MARKER BRILLIANCE and [EBL

MARKER INTERVAL DOWN-UP] , so that they may be easily read

3) After several minutes (3 minutes is convenient for later calculation), place the origin

of EBL on the previously plotted target position by shifting EBL ORIGIN JOYSTICK

to and fro in all directions

operation, EBL shows the relative heading direction of the target ship

5) Adjust the range by |VRM DOWN-UP|so that its marker touch to EBL The figures on the VRM indicator show CPA

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