IT2200 Reader System with Multimode Capability Installation & Maintenance/Service Guide
6-8
Reader System with Multimode Capability, all readers share the same downlink fre-
quency, which is generally set to 918.75 MHz. When using TDM, adjacent lanes can
be set to any of the uplink frequencies that are specified in the frequency plan (see
Table 6-1). The uplink frequencies in the adjacent lanes can be set to the same fre-
quency because one of the lanes is switched off when using TDM. This differs from
the traditional lane frequency plan. For example, a four-lane plaza using TDM could
have the frequencies shown in Table 6-2. Compare these settings with the frequency
settings for a system not using TDM as shown in Table 6-1.
Note: Where X delay and corresponding period and direction meet system needs.
Physical Remedies
By adjusting the angle or position of the downlink and uplink antennas, you may be
able to minimize cross-lane interference.
Warning
Switch off RF power before working on antennas.
Adjusting the Antenna’s Uptilt Angle
Lowering an antenna’s uptilt angle (the angle between the antenna cover and the hori-
zon) generally tends to reduce the interference (Figure 6-3).
Table 6-2 Frequency Settings Using TDM for Four-Lane Toll Plaza with TDM
Lane Downlink Frequency Uplink Frequency TDM Phase Delay
1 918.75 MHz 903.00 MHz 1 0
2 918.75 MHz 903.00 MHz 2 X
3 918.75 MHz 912.75 MHz 1 0
4 918.75 MHz 912.75 MHz 2 X
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