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Library Security Pedestal 2
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Revision 4.2
July 2008
6.4 Adjusting the Antenna Isolation
Once each antenna is tuned for optimal impedance (see section 6.3 “Adjusting the Antenna
Impedance”), it is necessary to verify the isolation of each antenna.
Correct antenna isolation is not greater than –19-20 dB or 600-mVpp residual peak-to-peak
voltages collected on either the top or bottom antenna when the center antenna is powered by the
tuning kit sine wave carrier generator. Poor isolation is approximately –10 dB or 2 Vpp residual
peak-to-peak voltages.
voltages collected on either the top or bottom antenna when the center antenna is powered by the
tuning kit sine wave carrier generator. Poor isolation is approximately –10 dB or 2 Vpp residual
peak-to-peak voltages.
Optimum isolation is obtained by sliding carefully the top or bottom antenna towards the fixed and
center antenna. When a minimum value is reached, the antenna position can be secured using the
4 screws.
center antenna. When a minimum value is reached, the antenna position can be secured using the
4 screws.
The voltage is measured using an oscilloscope of at least 100-MHz analog bandwidth, 10-ns time
resolution and a 50-Ohm cable terminated at the oscilloscope input.
resolution and a 50-Ohm cable terminated at the oscilloscope input.
6.4.1 Using the Antenna Tuning Kit
To access to the antennas remove the top cover of the L-SP2 pedestals (See section 4.3.3
“Installing the Pedestal”) and slide out the side panels from the L-SP2 pedestals chassis then set
up the components and connections as shown in
up the components and connections as shown in
Figure 32.
Table 5: Oscilloscope Settings
Parameter
Value
Figure 32: Antenna Tuning Isolation
L-SP2
Channel A
100 mV/Div.
Time Base
20 ns/Div.