Installation Guide Part 3

NGL FX Installation Manual Rev. * 75 of 84
CAUTION: In the presence of small resonances, this "spiky noise" will cause the system to false
alarm. Do not leave the system with this level of noise. The receiver gain must be set such that
Filter view 'D is nearly 'flat'.
Identifying and Eliminating a Resonance
A resonance is typically defined as a stationary signal in our band. When in the presence of noise a
resonance may be 'buried' in the noise. By definition, our tags are resonances (resonant circuits).
Our system alarms on resonant circuits on the frequency selected. Once the receiver is set to
acceptable levels of noise, the system must be adjusted to eliminate resonances in the environment.
There are two types of resonances: environmental item resonances and stationary resonances.
• Environmental item resonances are items that can be moved. Examples of environmental item
resonances that must be eliminated are: coils of wire, racks, wiring (Christmas lights) and, of
course, tagged merchandise. Environmental item resonances must be eliminated prior to final
setup.
• Stationary resonances are resonances that cannot be moved or resolved. These include: door
frames, checkout counters, and metal framed walls.
Remedying Resonances
To remedy both stationary resonances and environmental items resonances, the transmitter power
should be adjusted down to acceptable levels in Filter View 'C'. Figure 45 below shows the
reduction in transmitter power from TX@31 to TX@29 in Filter View 'C' will result in acceptable
levels to detect tags
The first figure below shows a low level resonance that is unresolved and could potentially cause
false alarms. The second figure shows the same resonance, but after reducing the TX level.
Figure 45: Unacceptable low level resonance, Filter View 'C' TX Power @31