WDS P20, Installation And Operation Manual

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16
5.6 Configuring the Redundant Transceiver
Chassis as a Repeater
Figure 5 on page 9 illustrates the use of a Redundant Station as a
repeater. Here are some specific requirements for repeater systems:
A) Antennas—Two antennas are required at repeater stations—one for
each radio. Measures must be taken to minimize the chance of interfer-
ence between these antennas. One effective technique for limiting inter-
ference is to employ vertical separation. In this arrangement, one
antenna is mounted directly over the other, separated by at least 4 feet
(1.22 Meters). This takes advantage of the minimal radiation exhibited
by most antennas directly above and below their driven elements.
Another interference reduction technique is to cross-polarize the
repeater antennas. If one antenna is mounted in the vertical plane, and
the other in the horizontal plane, an additional 20 dB of attenuation can
be achieved. (Remember that the corresponding stations must use the
same antenna orientation when cross-polarization is used.)
B) Interface Wiring—A null-modem cable (Figure 12) is required
between the
DATA INTERFACE
connectors of the two radios forming a
repeater station. This allows them to freely exchange data even though
they are both configured as DCE devices.
Invisible place holder
Figure 12. Data interface cable wiring for null-modem cable
Used for Repeater
2
4
8
7
2
3
4
8
7
3
TXD
TXD RXD
RXD
GND GND
DCD
DCD
RTS
RTS
P-20 #1
(DCE)
P-20 #2
(DCE)