Radar

Question 1

What is is multi-path error?

Answer 1

Multi-path is when a radio wave bounces back from i.e a mountain, back to the boat but the radar is transmitting and can’t pick up the signals, the radio wave therefore bounces of the ship back to the mountain and then back to the ship again where the radar can receive. This will make your target on your display at double the distance at the same bearing as the radio wave have travelled double the distance at the same bearing.

Question 2

What is side lobe error?

Answer 2

Side lobe is created from electromagnetic energy leaking from the side of the scanner. This creates lobes besides the main beam, these lobes can pick up targets at close range and therefore create false targets either side of the real target in the shape of a semi circle or sometimes even full circle. (cock n’ balls)

Question 3

What does a radar do?

Answer 3

Measures the time it takes for a radio wave to be transmitted, reflected and received through the Echo Range Principle and divides it by 2 to get a distance to a target and display it on a screen.

Question 4

What is bearing discrimination?

Answer 4

Radar’s ability to differentiate between 2 targets on different bearings at the same range.

Question 5

Name the 5 factors that affect the reflective properties of targets.

Answer 5

MASTS

Material
Aspect
Size
Texture
Shape

Question 6

What is Minimum range and what is it affected by?

Answer 6

The ability to detect and display echoes in close proximity to the radar.

Pulse length
Vertical beam width and height of antenna.

Question 7

What’s subrefraction?

Answer 7

Cold polar air over warm sea deflect beam upwards. 40% range reduction.

Question 8

What’s super refraction?

Answer 8

Increase of radar range when warm air is over cold air.

Question 9

What is ducting?

Answer 9

Temperature inversion.
Can increase radar range to 400nm if antenna is in duct

Question 10

Radar beam characteristics?

Answer 10

Horizontal beam width
0.5-2.0 degree

Vertical beam width
20-30 degree

Question 11

When would you select a longer range? (3 factors)

Answer 11

1. If you are concerned about distant weather
2. You want to acquire a target further than your current range
3. Wish to take a range of a distant object

Question 12

Considerations when using different ranges

Answer 12

Shorter range will be better for navigating and will have reduced range and bearing discrimination

Generally would have to increase pulse length when going to longer ranges which would increase range and bearing discrimination but would also let you potentially see upcoming targets/weather

Question 13

The difference between X band S band. Advantages and disadvantages of each

Answer 13

X band (3cm wavelength, 9GHz) has better definition, range discrimination and bearing accuracy. Affected more by rain than S band.

S band (10cm wavelength, 3GHz) has better range and less attenuation. Less sea clutter on S band therefore less probability of targets being masked

Question 14

What radar mode to be in for collision avoidance?

Answer 14

Relative motion display

Question 15

Explain blind and shadow sector

Answer 15

There is no radar performance in a blind sector, the beam is completely blocked. Some performance is possible in a shadow sector, especially when using S band

Question 16

How do you setup a radar?

Answer 16

Big Randy Girls take cock hard
1. Brilliance (set the brightness for your display)
2. Range (go to a suitable range)
3. Gain (turn up until you get white speckles)
4. Tuning (tune the receiver to get the best display, this is normally done automatic)
5. Heading (check so heading marker is not off, if it is means radar could be compromised)

Question 17

What are the radar components?

Answer 17

Power source, Transmitter (magnetron), T/R Cell (duplexer), Antenna (Scanner) (Also a motor to drive the antenna), Receiver/Amplifier, Display/PPI (Plan position indicator)