RADAR
SEMINAR
By Ron Davidson, SN
OUR OBJECTIVES
• Increase general radar knowledge & raise confidence of use
• Gain knowledge of radar types available
• Describe the advantages and limitations of radar & radar types
• Describe radar controls & their effects
• Interpret the radar display
• Learn some practical use knowledge
• Learn some installation & maintenance considerations
WHAT IS RADAR, AND HOW IS IT USED
• RAdio Dectection And Ranging
– Principles NikolaTesla - 1917; Practical British – 1935
• Collision Avoidance – Primary use
– Periods of reduced visibility (Darkness/Weather)
• Navigation - Situational Awareness – Secondary use
– Coastal and Inland
• Periods of reduced visibility or darkness
• Situational awareness – understanding surroundings
A BRIEF HISTORY OF RADAR
• 1917 – Principles established by Nikola Tesla
• 1935 – British – 1st patent for Air Defense
• 1950 – Decca – 1st Marine Radar
• 1969 – 1st FMCW (Broadband) – Atmospheric (Weather)
• 2000s – Marine FMCW & HD Radar
THE DEFINITIVE GUIDE TO YOUR RADAR
• The manufacturer’s operator manual!
TYPES OF RADAR AVAILABLE
• Traditional pulse radars – High power (2KW - 4KW) pulses; typical for
recreational boaters. Older Analog -> Newer Solid State
• Broadband radars – Continuous wave at low power (typically 1/10th of
cell phone power). Will not trigger RACONS.
• High Definition (HD) radars – Not really a type; typically a pulse radar
with additional signal processing performed to improve the sharpness
of display; similar processing to HDTV.
• Coming – Doppler Solid State UHD Radars
– Fast reaction, color coded display = red for approaching contacts.
– Display Course & Speed of contacts.
COMPONENT PARTS OF RADAR SYSTEMS
• Hardware
– Transmitter
– Receiver
– Antenna
– Cabling
– Display
– Mounting hardware
• Software
– Controls timing and signal processing for display.
HARDWARE CONTINUED - DISPLAY
• Heading Flash
HOW IT WORKS
In
Scanner
Unit
Transmitter
(Magnetron)
Receiver
Data Cable
Transmitted pulse
Received echo
Antenna
Display
Unit
RADIO WAVE TRANSMISSION
• Radiation from VHF antenna is omnidirectional
• Radiation from a radar antenna is unidirectional
RADAR BEAM TRANSMISSION
• Typically 5° Beam Width
with Radome antenna ~ 24 - 48 RPM
• 2.5° with open array (0.8° w/HALO 6’)
– Bigger footprint
– Caught in rigging
• 25° Vertically
RADAR BEAM WIDTH
• Long antenna = narrow beam ~2°
• Short antenna = wider beam ~5°
RADAR HORIZON – LINE OF SIGHT = VISIBLE + ≈ 05%
• Radar range is primarily a function of height
THINGS THAT EFFECT RADAR PERFORMANCE
• Atmospheric attenuation including precipitation
• Reflections off the sea, land, and other vessels that are unwanted
– Sea clutter
• Diffraction (bending around objects such as hull, masts, landforms)
• Refraction (bending due to atmospheric density)
• The size, shape and material of the targets illuminated
QUALITY OF RADAR REFLECTIONS
– Depends upon target
• Shape
– Flat specular
– Curved
– Flat turned
– Rugged
- excellent
- good
- poor
- fair
• Material
– Metal
– Fiberglass
– Wood
- good
- fair
- poor
RADAR REFLECTOR
• To ensure your vessel returns a strong echo.
– Install in “Rain Catcher” position
RADAR SHADOW
• Affects the display of objects and may make display confusing.
• Can hide objects of interest.
RADAR LIMITATIONS
• Of all navigational aids Radar is most difficult to interpret!
– Practice, practice, take a break, then practice some more!
• Cannot penetrate water very far, esp. sea water = sea clutter
• Subject to Line of Sight restrictions (cause of Radar Shadow)
• Power falls off by 1/Range4 : 2000W Tx ≈ 0.006W Rx @ 24 nm
ADVANTAGES / DISADVANTAGES
• Radar shows contacts in reduced visibility
• Single Freq Pulse
– Best for: Long range > 20 nm
– Power consumption of: 30 – 50 watts
• 2.5A @ 12V or 1.25A @ 24V (60 or 30 AH per day)
– Risks and Dangers of: Radiation hazard
• Broadband – Exceptional close range performance (20’!)
– Best for: Short range < 18 nm
– Power consumption of: ~20 watts
• 1.7A @ 12V or 0.8A @ 24V (41 or 20 AH per day)
– Risks and Dangers of: None
• Radar is most difficult to interpret what you’re seeing
PULSE VS BROADBAND - DISPLAY
BEARING RESOLUTION – BEAM WIDTH
RANGE RESOLUTION – PULSE WIDTH
• Automatically set by range selection
SETTING UP YOUR RADAR
• Typical Radar Controls (newer radars may be automated)
– Gain = receiver sensitivity
– Intensity/Brilliance = screen brightness
– Tuning = minor frequency adjustments
– Sea Clutter = Sensitivity Time Control (STC)
• Lowers receiver sensitivity close aboard
– Rain Clutter = Fast Time Constant (FTC)
• Adjusts sensitivity to “clip” weather echo
– Interference Rejection = Normally Off
• First - Set all controls to minimum setting or to off.
– Do this procedure every time you use the radar! Away from slip.
– Turn on power – allow warm-up to STBY
SETTING UP YOUR RADAR #2
• Toggle Tx/Stby so radar transmits.
• Set range to LR. Your definition of LR use…
• Turn Intensity up until you clearly see the sweep.
• Turn Gain up to see echoes, continue until noise appears, then reduce
until noise just disappears.
• Tuning (if present) adjust for best image of LR targets.
• Set range < 5 nm – Significant clutter around center.
– Set Sea Clutter for maximum target definition at close range.
GAIN ADJUSTMENT
• On LR - turn up until noise appears then down to minimum noise.
SEA CLUTTER ADJUSTMENT
RAIN CLUTTER ADJUSTMENT
NAV RULE 7 - RISK OF COLLISION
(a) Every vessel shall use all available means appropriate to the
prevailing circumstances and conditions to determine if risk of collision
exists. If there is any doubt such risk shall be deemed to exist.
(b) Proper use shall be made of radar equipment if fitted and operational,
including long-range scanning to obtain early warning of risk of collision
and radar plotting or equivalent systematic observation of detected
objects.
(c) Assumptions shall not be made on the basis of scanty information,
especially scanty radar information.
THE AFTERMATH – NO RADAR PLOTTING
• MS Stockholm & SS Andrea Doria – July 25, 1956
• Saw each other on radar for 29 minutes! Poor radar training of crews!!
INTERPRETING THE RADAR DISPLAY
34
boats
Contributed by: Kevin Monahan, “The Radar Book”
INTERPRETING THE RADAR DISPLAY
• Most difficult task to learn
– Must practice to maintain Situational Awareness.
• Overlay of radar on chart
– Offers GREATEST assistance in understanding display.
• Practice in fair weather
– To maintain confidence in foul weather or restricted visibility
• Heading Up (versus North Up) Mode = Relative Display
– Provides least confusing display of what skipper is seeing.
NAV RULE 19 - CONDUCT OF VESSELS IN RESTRICTED VISIBILITY
(a) This Rule applies to vessels not in sight of one another when navigating in or
near an area of restricted visibility.
(b) Every vessel shall proceed at a safe speed adapted to the prevailing
circumstances and conditions of restricted visibility. A power-driven vessel shall
have her engines ready for immediate maneuver.
(c) Every vessel shall have due regard to the prevailing circumstances and
conditions of restricted visibility when complying with Rules 4-10.
(d) A vessel which detects by radar alone the presence of another vessel shall
determine if a close-quarters situation is developing and/or risk of collision exists.
If so, she shall take avoiding action in ample time, provided that when such action
consists of an alteration in course, so far as possible the following shall be
avoided:
• (i) An alteration of course to port for a vessel forward of the beam, other than
for a vessel being overtaken;
• (ii) An alteration of course toward a vessel abeam or abaft the beam.
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•
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•
DISPLAY SHOWS RELATIVE (TO YOUR VESSEL) MOTION
Stationary objects (land, buoys, etc.) move straight down the display.
Moving objects show movement relative to your course.
Speed and movement is a vector of your speed & contact speed.
Magnetic Bearing = Relative Bearing + Compass Bearing
RADAR RANGES
• Most commonly used ranges – 1.5, 3, 6 nm
• Radar automatically sets pulse width and rate
• Range ring spacing and RPM automatic based upon range setting
COLLISION COURSE & CPA
• Contact on constant bearing toward center = collision course
• Use EBL – Place over target – if contact remains on EBL = collision course!
• Estimate distance & time: Three minute rule – Add two zeros to your speed =
# yards travelled in 3 minutes. i.e. 8 knots = 800 yards.
QUICKLY DETERMINING CPA
• Mark contact location with cursor or EBL & VRM
• After a few minutes, use straight edge and align contact original &
present positions.
• Draw a line (either mentally or physically) from center of screen to
nearest point on straight edge = Distance of CPA
• Many newer radars feature Mini Automatic Radar Plotting Aid (MARPA)
– Automatically track multiple targets.
– Usually requires input from a heading sensor (sold separately)
USE OF RADAR TRAILS (WAKES) TO ASSIST
RADAR INTERFERENCE
• Running Rabbits/Flash Strobes – Interference from other radars.
RADAR SYSTEM LIFE CYCLE
• How long do they last
– 3000 to 5000 hours is typical.
• Are repairs possible?
– Yes; depends on MFG Support availability.
• Overall cost of repair
– $$ - $$$ - Is it cheaper to buy new?
RADAR INSTALLATION
• Installation includes:
– mechanical mounting
– electrical wiring
– configuring the display or network system to work with the radar
– adjusting the radar for proper performance
SCANNER LOCATION
Radiation
Hazard!!
Keep 4.6’
from crew.
GENERAL MAINTENANCE
• remove any dust, dirt or sea salt from the external surfaces with a dry,
lint-free cloth.
• check that the radar components are held securely in place and that
the screws, nuts and bolts have not worked loose.
• check that all the radar cabling is not frayed, bent, or cut and that the
radar system cable connections are secure, tight and waterproof.
GENERAL TROUBLESHOOTING (K-I-S-S)
• Common problems are caused by:
–
#1 = Operator improperly setting controls!
– poor adjustment of the radar (particularly inadequate tuning
adjustment).
– Blown fuses, tripped circuit breakers.
– poor maintenance (particularly of the cables & connectors).
– faulty or loose contacts at switches and relay points.
• Check these first, before calling a technician.
GENERAL TROUBLESHOOTING
• If no image appears on the screen and screen shows message no
scanner detected:
– check radar scanner interconnect cable wiring & connectors.
• If no image appears on the screen and the screen shows message no
radar detected:
– check that the radar has power.
– check the data cable between the radar and the display system.
GENERAL TROUBLESHOOTING
• If the scanner is working but no image appears on the display:
– adjust gain and threshold brightness.
• If radar reception is poor:
– check for physical damage to the cables (such as fraying) and for
any loose/poor connections.
– check for water damage to the radome or to the cables between
the radar components.
RADAR SUMMARY
•
•
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•
Primary use – Collision Avoidance (<3 nm)
Secondary use – Navigation (3 – 6 nm)
Range is limited by height of scanner unit
Difficult to interpret display
Practice in fair weather
When integrated with Chart Plotter – improves situational awareness
• Practice – Practice –
Practice!
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DO YOUR RESEARCH…
QUESTIONS?
www.navico.com (Simrad, Lowrance, B&G)
www.raymarine.com
www.garmin.com
www.furuno.com