WI-MOD-E-100 & WI-MOD-E-300 Wireless Ethernet
User Manual
WI-MOD-E Manual v1.10
Page
12
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 the
section 6 of this manual.
Where it is not possible to achieve reliable communications between two WI-MOD-E modules,
then a third WI-MOD-E 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 WI-MOD-E 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 a single omni-directional antenna.
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 WI-
MOD-E 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 WI-MOD-E 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.
The net gain of an antenna/cable configuration is the gain of the antenna (in dBi) less the loss in
the coaxial cable (in dB). The maximum net gain of the antenna/cable configuration connected
to the TX/RX connector is 0dB in Europe (100mW ERP). In USA, Canada and Australia (4W
ERP), the maximum gain is 12dB for the WI-MOD-E -300 or 16dB for the WI-MOD-E -100.
There is no gain restriction for antennas connected to the RX connector.
