RADAR PRACTICE EXAM

Question 1

“RADAR” means ?

Answer 1

Radio Detection And Ranging

Question 2

Two methods of speed detection ?

Answer 2

Average speed method
Microwave Doppler method

Question 3

Why is cosine effect most common situation you will encounter as a radar operator ?

Answer 3

Ideally a target vehicle should travel directly towards the radar and in the centre of the effective beam however ideal conditions for the radar create a dangerous situation for the operator.

To overcome the danger the radar is operated from a point which is not directly in front of the target thus creating an angle between the direction in which the beam is transmitted and direction of travel of target.

Question 4

What is Doppler shift ?

Answer 4

It is the difference between the transmitted and received energy, radar emits electromagnetic energy which strikes the target and return to receiver, the difference is called Doppler shift

Question 5

As an operator what should you apply to keep the cosine angle within acceptable limits ?

Answer 5

7:1 ratio

Question 6

As an operator why must you maintain a reasonably constant patrol speed ?

Answer 6

To allow faster acquisition of patrol speed and more time calculating closing rate speed

Question 7

As an operator how do you know if the silver Eagle 2 radar is being subjected to Radio Frequency interference?

Answer 7

‘Rfi’ will be displayed

Question 8

Requirements of a valid speed check ?

Answer 8

Visual observation and estimation
of target speed
Observe the numerals in the patrol and target displays
Clear and constant tone (pitch may vary)
Correlation between patrol speed and checked
speedometer
Duration of the check(steps 2,3,4) must not be
less than 3 seconds
Minimum 200m between targets of similar size

Question 9

What needs to be fitted with HWP vehicles before being used for speed enforcement duties ?

Answer 9

Checked speedometer &
Shielded cable

Question 10

Why does the size of the target affect the range of the Radar?

Answer 10

Radar obeys inverse Square Law.
It considers the reflective area of the target and the amount of energy reflected from the target. And the distance between the antenna and the target

Question 11

What range of speed will the
Silver Eagle 2 Radar measure ?

Answer 11

Target speed 16km/h to 320km/h
Patrol speed 16km/h to 239km/h

Question 12

Under what circumstances is the radar likely to encounter an add on speed ?

Answer 12

When police vehicle is moving less than the threshold speed of the radar 16km/h)

Radar treats any on coming vehicles within
50m as a stationary object and displays the
closing rate speed as patrol speed and no
target is displayed.

Question 13

When operating the radar is moving
mode, as the operator what would you do to negate the possibility of a Gross Error’ ?

Answer 13

Correlate with patrol speed and checked speedometer

Question 14

How will interference commonly affect the radar?

Answer 14

Display of target speed in the absence of target
No Displayed speed when a target is
present

Question 15

List when the radar must be tested and who performs these test

Answer 15

At the start of the shift
Every hour
At the conclusion of the shift
When it is taken to REU every 12 months
And the operator does the check

Question 16

For a section 137 certificate to be tendered as a Prima facie evidence, it must be tendered within what period of time ?

Answer 16

12months receding from the offence

Question 17

You are operating the radar when a split speed occurs explain what happens to the radar as a result of this effect ?

Answer 17

Occurs in speeds in excess of
120km/h
The instrument is unable to
obtain the patrol speed from the roadway in
front of the vehicle and obtain it speed at some angle
As a result of the cosine effect the displayed
speed is lower than the true patrol speed
Radar obtains true ground speed but because
it already has a patrol speed, treats it as
Closing rate speed
The displayed patrol speed is subtracted from
the closing rate speed and the differences displayed as target speed
When target and display are added together
the total will equal the true patrol speed +-
2km/h

Question 18

As a operator how would you know the multipath interference has occurred ?

Answer 18

Display goes blank and short blips occur

Question 19

Doppler tone ?

Answer 19

Doppler shift frequency divided down for listening comfort Stationary mode divided down by 6
Moving mode divided down by 12

Question 20

Explain what is likely to happen when Radar encounter differential effect?

Answer 20

Occur in moving mode
When a target is checked whilst a large reflective vehicle( such as a
truck or caravan) is immediately in front of the police vehicle radar treats it as stationary object. Whilst acquiring patrol speed a stronger reflection may be obtained from the vehicle in
front resulting in the difference in speed between the two vehicles displayed as patrol speed. Once the patrol speed is established the instrument searches for the higher velocity generated by combined target and patrol speed

Question 21

Explain what happens when the Radar encounter Double Bounce ?

Answer 21

This occurs in the absence of target when there is large
stationary structures like bridges,
Bill boards and road signs. The beam sent by the radar strikes these stationary structures and returns to the police vehicle and bounces back.
The Radar then treats the police vehicle as host and target. The amount of energy arriving at the antenna as a result of double bounce

Question 22

What evidence must you give if there is change in the pitch tone ?

Answer 22

Evidence in change of speed

Question 23

Whilst checking the radar you notice that the tamper proof seal has been violated. What must you do?

Answer 23

Inform the supervisor, take device off from service, write a manuscript report detailing the issue and forward it to REU for repairs and investigation.