Radar Flashcards
What does RADAR stand for?
Radio Detection and Ranging
What type of energy is transmitted by the Eagle 3 radar?
A continuous wave of electromagnetic energy
What is the transmitted frequency of the Eagle 3 radar?
34.9 GHz i.e. (34900 million Hertz) cycles per second
What is the wavelength transmitted from the Eagle 3 radar?
8.59 millimetres
What is the spread/width of the Eagle 3 radar?
The radar beam leaves the antenna and spreads out at an angle of 12 degrees (plus or minus 1 degree). This equates to 21 metres of spread for every 100 metres the beam travels forward. Effective length is nominally 600 metres.
What is the operating voltage of the Eagle 3 radar?
9.0 – 16.5 Volts DC
What does ‘LO’ mean when it appears on the radar instrument?
‘Lo’ will appear in the target speed display when the power supply voltage drops below the minimum operating voltage, ie 9.0 volts
What are the operational temperature ranges for the Eagle 3 radar?
- 30 degrees Celsius up to + 60 degrees Celsius.
What target speeds is the Eagle 3 capable of detecting?
16km/h – 330 km/h
What patrol speed is the Eagle 3 capable of detecting?
16km/h – 160 km/h
Combined patrol and target speeds will not exceed 330 km/h.
Why is reflection important to the operation of the Eagle 3 radar?
The Eagle 3 radar relies upon energy being reflected from an acquired target to operate.
What is Doppler tone?
The Doppler tone emitted by the Radar system is the Doppler shift frequency divided down for listening comfort.
• Divided by 6 in stationary mode, due to only one target moving
• Divided by 12 in moving mode, due to two vehicles moving
Why is a clear tone important during a valid speed check?
A clear tone indicates that the radar is monitoring only one target and is not being subject to any interference.
What is Doppler shift?
Doppler shift is the actual frequency change which takes place as a result of movement between antenna and target.
How can an operator check for segment faults in the display of the Eagle 3 radar?
Depressing and holding the ‘test’ button will illuminate all the displays. Upon releasing the ‘test’ button the Eagle III will complete an internal test sequence.
How does interference commonly affect the Eagle 3 radar?
Interference has 1 of 2 effects:
1. Display of a speed in the absence of a target
2. No displayed speed when a target is present
Interference DOES NOT add or subtract from any target speed reading.
What happens to the Eagle 3 radar when subjected to radio frequency interference (RFI)?
Radio Frequency detector is activated and causes the displays to blank and ‘rFI’ will be displayed.
Is the Eagle 3 radar capable of registering the speed of a motorcycle when a truck is in sight? Explain.
Yes, it is possible. However, the radar obeys inverse square law. Therefore, the truck having a larger reflective surface than a motorcycle would reflect more energy at a greater distance. The motorcycle would have to be much closer than the truck for the radar to register the speed of the motorcycle.
Explain inverse square law.
The amount of energy returned to the radar antenna from a target will be determined by two main factors:
1. The reflective area of the target (target size)
2. Distance between the radar antenna and target.
Why is it important to correlate the patrol speed with the checked speedometer during speed checks?
To ensure the radar is not subjected to any interference/s and to negate the possibility of an incorrect speed (patrol speed) being displayed as the result of an effect.
Prior to performing speed enforcement, operators must perform the following checks in relation to the checked speedometer at the commencement and conclusion of their shift. What are those checks?
- Visual check of the speedometer and wiring for any damage
- Ensure the two tamper-proof seals are intact and not damaged in any way.
- Turn on the digital speedometer and observe all segments on the 7-segment displays. Ensure all segments illuminate.
- At the commencement of your patrols conduct a correlation check of the digital speedometer and the patrol speed of the radar. Verify the accuracy of the digital speedometer is within +2 km of the patrols speed displayed on the radar.
- If there is a difference greater than + 2km/h or tamper-proof seals are violated all speed enforcement shall cease immediately and brought to the attention of the supervisor.
What is multipath interference?
It is two energies arriving at the receiver at different time intervals. It causes short blips on the audible tone and only occurs for very short periods.
• It is likely to occur on long straight roads where there is Armco railing and or similar barriers.
• Does not affect accuracy of speed readings.
• May cause the display to blank.
What are some examples of natural interference?
- Large trees
- Bushes
- Heavy rain
- Snow
- Windblown dust; and
- Fog
What are some examples of manmade interference?
- Large advertising signs, especially if they are moving
- Large broad bladed fans
- Fluorescent lights
- Power transformers
- X-ray machines
- Radio transmitters
- Mobile phones