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RADAR > RADAR Theory > Flashcards

RADAR Theory Flashcards

1
Q

What does RADAR stand for?

A

Radio Detection and Ranging

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2
Q

What type of energy is transmitted?

A

A continuous wave of electromagnetic energy.

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3
Q

Size of Wavelength?

A

8.59mm

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4
Q

Operating voltage?

A

9.0 to 16.5 volts

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4
Q

Spread / Width of RADAR beam?

A

12 Degrees (+/- 1 Degree)
21m for every 100m

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5
Q

What does ‘Lo’ mean?

A

Appears in the target speed display window when the power supply voltage drops below the minimum operating voltage.

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6
Q

Operating Temprature?

A

-30 degrees to +60 degrees

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7
Q

Target speed range?

A

16km/h to 330km/h

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8
Q

Why is reflection important for operation?

A

RADAR relies upon energy reflected from the target to operate

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9
Q

What is Doppler Tone?
VERBATIM

A

The Doppler tone is the doppler shift frequency divided down for listening comfort
Stationary = Divided down by 6
Mobile = Divided down by 12

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10
Q

What is the importance of a clear tone in a speed check?

A

A clear tone indicates that the RADAR is only monitoring 1 target and that there is no interference.
Any change in pitch must be accompanied by evidence of altering speed.

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11
Q

Transmitted frequency?

A

34.9GHz (speed of light)

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12
Q

Patrol speed range?

A

16km/h, but may sometimes display speeds as low as 9km/h. Up to 160km/h.
Combined and Patrol speed will not exceed 330km/h

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13
Q

What is Doppler Shift?

A

It is the actual difference (change) between the transmitted and received frequencies as a result of movement.
Caused by relative velocity

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14
Q

Internal test Sequence

A
  • All segments illuminated
  • Pas displayed in target speed area and patrol speed area
  • Crt, Pas and days until calibration due
    displayed
  • Ant F2 r0 displayed indicating front antenna connected
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15
Q

How does interference affect RADAR?

A
  1. Display a speed in the absence of a legitimate target.
  2. No speed displayed where there is a target present.
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16
Q

Radio Frequency Interference

A

rFi will appear in target window

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17
Q

Inverse Square Law

A

The amount of energy returned to the radar from a target depends on:
1. The reflective area of the target (target size).
2. Distance between the radar antenna and the target.

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18
Q

Importance of speed correlation during speed checks

A

During Setup:
- To ensure correct antenna alignment.
During Speed Check:
- To ensure the radar is not subjected to any interference or effect.
- To ensure there is no gross error

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19
Q

Types of interference and how each affects the radar beam

A

Natural Interference – Causes a decrease in effective range of the radar.
Heavy Rain – Heavy, driven rain falling as a significant angel to the roadway can add to or subtract from correct patrol speed and may cause some reduction in effective range.
Man-Made Interference – Causes a speed reading or a reduction in effective range.
Electrical Interference – Negated by the use of shielded cables.

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20
Q

Examples of Natural Interference

A
  • Large trees
  • Bushes
  • Heavy rain
  • Snow Falling
  • Windblown dust particles
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21
Q

Examples of Man-Made Interference

A
  • Large Advertising signs
  • Large bladed fans
  • Mobile phones
  • X-ray
  • Bridges
  • Radio Transmitters
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22
Q

Length of RADAR beam

A

Beam is infinite but the effective length is nominally 600 metres.

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23
Q

What is a gross error?

A

Error of 3km/h or greater

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24
Q

What is Multi-path Interference?

A

Multipath Interference is 2 energies arriving to the receiver at different time intervals. It causes short blips in the audible tone and only occurs for very short periods.
- It is likely to occur on long straight roads where there is Armco railings and/or similar barriers.
- Does not affect accuracy of speed readings.
- May cause the displays to blank.

25
Q

In moving mode what 3 functions must the radar perform?

A
  1. Determine and display patrol speed.
  2. Determine combined speed of radar and target.
  3. Determine and display target speed.
26
Q

In moving mode what must the radar instrument obtain?

A

It must obtain 2 doppler shift frequencies. Patrol speed (low doppler) and combined speed (high doppler).

27
Q

How is patrol speed obtained?

A

From the energy reflected off the roadway or surrounding stationary objects. Ideally 7 metres to the front of the patrol vehicle.

28
Q

Speed tolerance for correlation?

A

Within + / - 2km/h

29
Q

4 behaviours associated with radar energy

A

Reflection:
The radar relies on energy being reflected from the target to operate.
Refraction:
When a ray of light meets the surface of separation between two transparent media, it is sharply bent or refracted when entering the denser medium.
Diffraction:
When electromagnetic waves are restricted by an aperture or by the edge of an obstacle, some of the energy spreads into the region not directly in line with the source.
Absorption:
Frequency will be absorbed by some compounds, most common of which is water.

30
Q

RADAR tolerance

A

Stationary = + / - 1km/h
Moving = +1km/h / - 2km/h

30
Q

Tuning Forks

A

Big = 45km/h (represents patrol speed)
Little = 80 km/h (represents CRS)
Difference = 35kmh

31
Q

Importance of constant patrol speed?

A
  1. To allow easier and faster acquisition of the patrol speed.
  2. Allows more time being devoted to calculating Closing Rate Speed.
32
Q

Main points for conducting tuning fork testing?

A
  • Used to verify the accuracy of the RADAR by simulating the frequency increase caused by a moving target.
  • To establish that the transmitter/ receiver is functioning.
  • To establish the accuracy of the logic control unit.
32
Q

Testing procedure
(VPCCC)

A

Must be conducted at the start and finish of every shift.
1. Visual Check - correct antenna placement/alignment
2. Press Power. Observe all segments illuminate. Observe internal test. Clear tuning fork test with tick.
3. Check audio setting
4. Check range setting
5. Carry out tuning fork test

32
Q

Care of tuning forks

A
  • Never strike them against anything harder than the fork or against themselves.
  • When not in use, should be carried in the police vehicle.
  • Mechanical and Electronic tuning forks must go with RADAR when sent to REU for repair or calibration.
33
Q

Requirements for a valid speed check.
VERBATIM
(VOCCDM)

A
  1. Visual observation and estimation of the target’s speed.
  2. Observe the numerals in the patrol speed and target displays.
  3. Clear and continuous tone (however pitch may vary).
  4. Correlation between patrol speed and checked speedometer.
  5. Duration of the check (steps two, three and four) must not be less than 3 seconds.
  6. Minimum of 200m distance between targets of a similar size.
34
Q

Operational Guidelines

A
  1. Radar / Lidar is to be set up and tested as per instructions.
  2. At all times the instrument is to be in ‘hold’ mode until a target is visually observed.
  3. Whilst patrolling, police vehicles must maintain a reasonable, constant patrol speed.
  4. The minimum detection time is 3 seconds for a valid radar speed check.
  5. Ensure a clear audio tone is heard throughout the period of the check.
  6. Radar / Lidar must not be used in inclement weather.
  7. Avoid subjecting the radar display unit to direct sunlight for extended periods.
35
Q

Section 137 Certificate

A

Must be issued within 12 months from the date of the offence.

36
Q

4 exemptions to having speed measuring evasion articles?

A
  1. The person was going to surrender the article.
  2. The person did not know, or could not have reasonably known the article was fitted or being carried.
  3. The device was not built as an article.
  4. The vehicle was subject to a notice, requiring removal of the article within a specified time, and the notice had not expired.
37
Q

When must the radar be tested and by whom?

A
  1. At the start of the shift (By the operator).
  2. At hourly intervals (By the operator).
  3. At the end of the shift (By the operator).
  4. Every 12 months (By the REU).
38
Q

What must a vehicle be equipped with for radar operation?

A
  1. Checked speedometer.
  2. Shielded cable.
39
Q

In moving mode can the speed of a vehicle be checked when travelling in the same direction?

A

Yes, however the target vehicle would have to be traveling at twice that of the patrol vehicle plus the threshold. Even then the display would be the threshold speed. (This feature has been disabled in the Eagle 3 but is still in manual)

40
Q

What is relative velocity?

A

The component of speed that travels directly towards the radar.

41
Q

Antenna set up

A
  • 1m-2m above ground level.
  • Face front and parallel with the roadway in moving mode.
  • Face front or rear and parallel with the roadway in stationary mode.
  • Protection cover must not be removed by operator.
  • Any repairs to the antenna are to be completed by REU.
  • Antenna must be not used in inclement weather.
42
Q

Why should radar be used when traffic is light?

A
  • Easier target identification.
  • As to comply with the only one vehicle of a similar size within 200m.
43
Q

Responsibilities of using the RADAR

A

1- Within 50 metres of a speed change (60km/h zone becoming a 50km/h zone) unless;
A. Speed is excessive (20 km/h of the speed limit).
B. Subject of complaint.
C. Where there is a high accident history.
* this does not apply to school zones.
2. At any location bring legitimate criticism or give rise to the complaint that they are a means of raising Government revenue.
3. When operating speed measuring instruments police should be aware of Australian Design Rules for motor vehicle speedometers.

44
Q

What is interference?

A

Any external event which adversely influences the normal operation of the radar.

45
Q

5 Main Effects

A
  1. Cosine effect
  2. Spilt speed
  3. Add-on speed
  4. Differential effect
  5. Double Bounce
46
Q

Cosine

A
  • Cosine Effect is the angle between the direction in which the beam is transmitted and the direction of
    travel of the target.
  • Ideally the target should travel directly towards the radar in the centre of the effective beam, However, this would create a dangerous situation. To overcome the danger, the radar is operated offset to the target creating an angle.
  • Apply 7:1 ratio to overcome cosine
  • Speed checking cannot be done within cosine range
47
Q

Differential Effect

A
  • May occur in moving mode when a target is checked whilst a large reflective vehicle (caravan or truck) is immediately in front of the police vehicle.
  • When obtaining patrol speed, stronger reflection may be obtained from vehicle in front causing the difference in speed between the 2 vehicles as patrol speed.
  • Displayed target speed is in error by the difference of the 2 patrol speeds.
  • Use correlation to know it’s happening.
48
Q

Double Bounce

A
  • Will only occur in the absence of a legitimate target due to its large difference in signal strength.
  • Energy is reflected from patrol vehicle to stationary and back out again.
  • Police vehicle becomes host vehicle and target vehicle.
  • Creates false Closing rate speed being patrol speed and speed beam comes back to RADAR (2x true patrol speed).
  • Target speed will be same as true patrol speed +/-2km/h.
  • Keep RADAR in hold until legitimate target is observed to avoid.
49
Q

Spilt Speed

A
  • Occurs when police vehicle travelling in excess of 120km/h.
  • Unable to obtain patrol speed from in front, obtains it from an angle, because of cosine displayed patrol speed is lower than actual.
  • RADAR obtains true ground speed, treats it as CRS.
  • Displayed patrol speed subtracted from CRS and difference displayed as target speed.
50
Q

Add-on Speed

A
  • Usually Occurs at low speeds when police vehicle is below RADAR’s threshold (16km/h) and instrument must still obtain patrol speed.
  • Any oncoming vehicle within about 50m provides better signal than ground, and treat it as stationary.
  • RADAR will display CRS between the RADAR and oncoming vehicle as patrol speed.
51
Q

Digital Speedometres - Checks at Commencement and Completion of shift

A

The following checks must be completed at
commencement and completion of shift:
- Visual check of speedo and wiring for any damage.
- Ensure tamper proof seals are intact and not damaged in anyway.
- Turn on speedo and observe all segments of the 7 segment display, All segments must illuminate. If not, cease all speed enforcement and contact REU.
* At commencement of shift a correlation between digital speedo and RADR patrol speed. Must be within +/- 2km/h.
- Done on straight, flat stretch of road, with constant vehicle speed.
- Any speed difference of +/- 2km/h or tamper proof tags are damaged, cease all speed enforcement and report to supervisor and REU.

52
Q

Mechanical Tuning Fork Test

A
  1. Press POWER and observe internal test sequence. Flo will be displayed in target speed area and TEST will flash in lower right corner.
  2. Vibrate ’45’ fork and hold about 15cm away from antenna - observe ’45’ in patrol speed area and ‘PAS’ in locked speed area. Upon successful test ‘FHi’ is displayed in locked speed area.
  3. Vibrate ’80’ and hold about 15cm away from antenna - observe ’80’ in patrol speed area and ‘PAS’ in locked speed area.
  4. RADAR will automatically conduct moving mode test. Successful test indicated by:
    * ’35’ in target speed
    * ’45’ in patrol speed
    * ‘PAS’ in locked speed
    FOLLOWING TEST:
    * Correlate patrol speed with digital speedo
    * Select hold and continue patrol
    * Perform calibration test by pressing tick button on hourly intervals.
53
Q

Electronic Tuning Fork Test

A
  1. Press POWER and observe internal test sequence. Flo will be displayed in target speed area and TEST will flash in lower right corner.
  2. Point remote at antenna no further than 15cm away and press LOCK/REL button.
  3. Observe testing sequence to verify successful test
  4. If incorrect signal has been measured ‘Err’ will be displayed in patrol speed. Cannot complete test procedure until correct signal is measured
    FOLLOWING TEST:
    * Correlate patrol speed with digital speedo
    * Select hold and continue patrol
    * Perform calibration test by pressing tick button on hourly intervals.
54
Q

Doppler Shift - Stationary Mode

A

1km/h x 64.6

55
Q

ADJUSTING DOPPLER AUDIO SQUELCH/
UNSQUELCH

A

In audio menu toggle the Audio Squelch/Unsquelch by pressing touch screen area above or below the ‘Sq’ or ‘Un” indicator.

56
Q

Power Source

A

Fitted with two-conductor shielded cable and
a blue mini-Anderson plug.

57
Q

What must you do to negate the possibility of a gross error?

A

Correlate between patrol speed and checked speedometer.

RADAR (1 decks)

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