User's Manual

18 MDS TransNET I/O Guide MDS 05-2708A01, Rev. A
Antennas
Two antennas are required at repeater stations—one for each radio. Measures
must be taken to minimize the chance of interference between these antennas.
One effective technique for limiting interference is to employ vertical
separation. In this arrangement, one antenna is mounted directly over the other,
separated by at least 10 feet (3 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.)
System Addresses
The two radios that are wired together at the repeater site must have different
system addresses. To set or view the system address, see “ADDR [1...65000]”
on page 26.
Interface Wiring
A null-modem cable (Figure 15) 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 15. Data interface cable wiring for null-modem cable
(used for traditional repeater)
Interface Wiring
A single-radio repeater is formed by connecting TXD (Pin 2) and RXD (Pin 3)
on the
DATA INTERFACE connector together as shown in Figure 16.
Invisible place holder
Figure 16. Data interface cable wiring for single-radio repeater
DB-25
DATA INTERFACE
CONNECTOR
2
3
TXD
RXD
Pins 2 & 3
Connected Together
for Single-Radio Repeater