Installation Manual

F10 Installation Manual Rev. *60 59 of 71
Figure 6.5 Noise on Filter View D – Graph After RX Gain Tuning
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'.
Resonance Sources
A resonance is typically defined as a stationary signal in this FM band. When in the presence of
noise, a resonance may be ‘buried.’ By definition, Checkpoint tags are resonances (resonant
circuits). The system alarms on resonant circuits on the pre-selected frequency. Once the receiver
is set to acceptable levels of noise, the system must be adjusted to eliminate resonances in the
environment.
The two types of resonances are environmental item and stationary resonances, described below:
• Environmental item resonances are items that can be moved. Examples of environmental item
resonances that must be eliminated include 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
If stationary and/or environmental items resonances, the transmitter power should be adjusted
down to acceptable levels in Filter View 'C'. Figure 6.6 shows the reduction in transmitter power
from TX@31 to TX@29 in Filter View 'C' will result in acceptable levels to detect tags.
Note: The FCC requirement is TX=31 (same as CE).