D2 W MDME 2400 Wireless Ethernet Modem
IF 1584 Rev. 1
IF 1584 Rev. 1
Page 10
Line-of-sight paths are only necessary to obtain the maximum range. Obstructions will reduce
the range, however, may not prevent a reliable path. A larger amount of obstruction can be
tolerated for shorter distances. For short distances, it is possible to mount the antennas inside
buildings. An obstructed path requires testing to determine if the path will be reliable - refer to
Section 6 of this Instruction Sheet.
Where it is not possible to achieve reliable communications between two D2 W MDME 2400
modules, then a third D2 W MDME 2400 module may be used to receive the message and re-
transmit it. This module is referred to as a repeater. This module may also have a host device
connected to it.
The D2 W MDME 2400 unit has two antenna connections at the top of the module, allowing two
antennas to be fitted to the unit. The left connector (looking at the front) labeled “RX” is
connected only to the internal wireless receiver. The right connector labeled TX/RX is
connected to both the transmitter and receiver.
Note: when only one antenna is used, it must be connected to the right TX/RX connector.
Plant and Factory Installations.
Most installations in industrial plants and factories use single omni-directional antennas.
Installations can suffer from “multi-path fading” effects where multiple reflected radio signals
adversely affect the signal strength. This can be checked by moving the antenna a short distance
(10 cm or 4 inches) - if the signal increases significantly, then there are multi-path effects.
In a “static” installation, where the radio path is not changing, moving an antenna to the position
of maximum signal solves this problem. However, where the radio path changes because the D2
W MDME 2400 is mounted on moving equipment, or if there is moving equipment in the area,
then the solution is to use two antennas. Because the two connectors are separated, the RF signal
at each connector will be different in the presence of multi-path fading. The D2 W MDME 2400
unit will automatically select the higher RF signal.
Note that directional antennas are not normally used in plant and factory installations.
Line-of-sight Installations.
In longer line-of-sight installations, the range may be increased by using a high gain antenna on
the TX/RX connector. However, the gain should not cause the effective radiated power (ERP) to
exceed the permitted value. A second higher gain antenna can be connected to the RX connector
without affecting ERP - this will increase the operating range, provided the background noise in
the area is low.
Antennas.
Antennas can be either connected directly to the module connectors or connected via 50 ohm
coaxial cable (e.g. RG58 Cellfoil or RG213) terminated with a male SMA coaxial connector.
The higher the antenna is mounted, the greater the transmission range will be; however, as the
length of coaxial cable increases, so do cable losses.
