RADAR Flashcards
Pulse Length
Short/Medium/Long depending on range scale in use.
Short pulse- better definition
Long pulse-better range
Carrier Frequency
Radio frequency on which the transmission is made.
(X or S band)
X band
+ state preferred adv.
3cm about 10 GHz
Better Resolution, preferred for navigation.
What is attenuation?
Which band frequency suffers most?
the loss or reduction
of signal strength
over distance or
through a medium (rain)
X band suffers from attentuation more than S band.
S Band
+ state preferred adv.
10 cm about 3 GHz
Better in rain, longer range.
Sea Clutter (or STC; Sensitivity Time Constant)
+Correct setting?
It reduces the sensitivity of the receiver from the centre out.
Proper Setting: Clutter reduced, echoes distinguishable.
Precipitation Clutter
Suppresses reflected echoes from rain, hail or snow to clear the display.
Via video processing it doesn’t display leading edge returns.
Detection Characteristics of Radar Targets
MASTS
Material
Aspect
Size
Texture
Shape
RADAR meaning
RAdio Detection And Ranging
Setting up a Radar
(3 points)
- Check scanner is clear
- Turn ON
- BIG RANDY GIRLS TAKE COCK
Brilliance
Range
Gain - light background speckle (70%)
Tuning - need to be receiving something even if it is own wake. REFER TO MANUAL.
Clutter- Sea and Rain
Pre departure radar checks
(+ every 4 hrs WATCH min)
(list 6 steps)
then done < 4 hrs of radar watch.
(MGN 379)
- On + Running
- Performance Monitor
- VRM against range rings
- EBL using charted object with heading marker against compass
- Heading Marker Alignment
- Parallel Index lines if in use.
Good Radar Practice
(5 points)
CHAPS
1. Clutter controls
2. Heading Marker
3. Awareness
4. Performance
5. Shadow/Blind Sectors
- Clutter controls set to match conditions. Echoes may be obscured by sea/rain clutter.
- Check the heading marker alignment. Misalignment of heading marker can lead to misinterpreting collision situations.
- Aware that small vessels, ice and other floating objects may not be detected by radar.
- Quality of radar performance checked regularly using performance monitor
- Aware of Shadow/Blind Sectors. Masts or other structural features may cause shadow or blind sectors on display.
Performance Monitor
Verifies the radars ability to detect targets and provide accurate information.
Will also identify issues or faults within the radar system.
Read the manual for your particular radar.
Ensure radar range rings are on.
Radar Displays
H-Up : Un-stabilised- does not utilise heading input. Reverted to after heading input failure.
C-Up : Stabilised - heading input from a Gyro or transmitting heading device (THD)
N-Up : Stabilised - heading input from a Gyro or transmitting heading device (THD)
Ground stabilisation
(6)
- Coastal Navigation
- COG + SOG input
- Speed and Heading from GNSS
- Set and Drift visually shown
- difficulty determining true aspect
- fixed target will appear stationary
Sea Stabilisation
(6)
- Collision Avoidance
- CTW (Gyro) + STW (Log) input
- Speed and heading from Gyro and Log
- Doesn’t account for set and drift
- true aspect easily determined
- fixed target will have a vector, the reciprocal showing set and drift.
Errors of Radar
(8)
- Side Lobe effects (leaky energy)
- False Echoes (ie overhead power cables)
- Radar Interference (IR control)
- Indirect echoes (aspect)
- Multiple Echoes (echoes on same bearing)
- Shadow Sectors (Small area)
- Blind Sectors (large area)
- Radar Horizon (refraction-atmospheric conditons)
How do you make sure your heading marker is aligned?
- Check that the heading marker is aligned with the true compass bearing of the ship
- ensure that the heading marker line on the display is aligned with the fore and aft centreline of the ship. (need a visual AND conspicuous target dead ahead)
How do you set you radar up for a SART?
On the X band radar as most vessels have one:
big randy girls take cock
(BIG) Brilliance: N/A
(RANDY) Radar range scale set to 6/ 12 miles.
(GIRLS) Gain: Normal
(TAKE) Detune the radar: this reduces the clutter without reducing the SART echo.
(COCK) Clutter controls:
-Sea clutter set to min.
-Rain Clutter to match conditions/doesn’t matter
What could be fitted to a navigational mark to make it more radar conspicuous?
A racon or radar reflector.
When should you not adjust your heading marker?
-when alongside a berth
-using bearings of targets which are close to the vessel, not distinct or have not been verified visually.
