Serial Output Mode; Performance Tips; 1 How Radar Works; 2 Interference Sources - Decatur Electronics Genesis VP Directional User Manual

If you lock the speed of the fast vehicle, the LOCK and FAST icons will
designate that the locked speed is a faster target lock If these icons
do not appear, the lock is on the strongest target

4. Serial Output Mode

The Genesis-VPD has an RS232 communications port on the side
panel Using a custom RS232 communications cable, you can
connect the Genesis-VPD and transmit data to display signs, in-car
video and PCs for recording and analyzing speed data The serial
communication has the following characteristics (8:n:1) and is
transmit only:
One (1) start bit
Eight (8) data bits
No parity
One (1) stop bit
Transmission at 1200 baud
The unit transmits data as ASCII symbols in the following digit
sequence:
ASCII [hundreds][tens][ones]
Carriage return<CR>
(<CR> = ASCII decimal value 13)
The radar unit sends the data in this sequence when the TARGET
speed display changes When you press the LOCK button, the radar
transmits the following digital sequence:
[hundreds][tens][ones]<CR>
(<CR> = ASCII decimal value 13)
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5. Performance Tips

Understanding potential radar interference and what to do when it
occurs can greatly increase the radar's performance

5.1 How Radar Works

Determining a vehicle's speed begins with the radar gun transmitting
a beam of microwave energy (radio waves) at an approaching or
departing target vehicle When energy from this beam strikes a
vehicle, a small amount of the beam is refected back to the antenna
The refected signal frequency shifts by an amount proportional to
the speed of the target vehicle This is known as the Doppler efect
The radar device then determines the target vehicle speed from the
diference in frequency between the refected and transmitted signal

5.2 Interference Sources

When properly installed and operated, Doppler radar technology
is accurate and reliable However, variations in the environment
can cause situations and circumstances which can cause spurious
responses which are readily identifed by a qualifed operator Signs
that a speed is spurious can include the following characteristics:
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• A valid target motor vehicle speed in the operational range will
always override the source of interference and will be confrmed
by the audio component (See Sections 5 2 2 through 5 2 7 )
• The Doppler tone will lack the pitch and clarity component..
• Speeds are irregular.
• Speeds appear to track with the engine speeds.
5.2.1 Angular Interference (Cosine Efect)
The Cosine Efect causes the system to display a speed which is
lower than the actual vehicle speed This condition occurs when
the targeted motor vehicle's path is not parallel to the antenna,
including conditions such as the motor vehicle traveling on a curve
or a hill
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