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Cooper Bussmann 945U-E Wireless Ethernet Modem & Device Server User Manual
13
Rev Version 2.14
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 any interference in the direction of the link is low.
Antenna Gain and Loss
Antennas can be either connected directly to the module connectors or connected via 50-ohm coaxial cable
(for example, 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, cable losses also increase as the length of the
coaxial cable increases.
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 945U-E maximum net gain for US and Canada is 10dB (4W ERP) and 0dB for Australia and NZ (1 W
ERP). There is no gain restriction for antennas connected to the RX connector unless “TX Diversity” is enabled on
the Radio page.
The gains and losses of typical antennas are as follows.
Antenna
945U-E Gain (dBi)
Dipole
0 dB
Collinear
5 or 8 dBi
Directional
10–15 dBi
Cable Loss
dB per 30 m / 100 ft
RG58 Cellfoil
-9 dB
RG213
-7.4 dB
LDF4-50
-2 dB
The net gain of the antenna/cable configuration is determined by adding the antenna gain and the cable loss. For
example, an 8 dBi antenna (5.8 dBd) with 10 meters of Cellfoil (3 dBd) has a net gain of 2.8 dB (5.8 dB–3 dB).
Installation Tips
Connections between the antenna and coaxial cable should be carefully taped to prevent ingress of moisture.
Moisture ingress in the coaxial cable is a common cause for problems with radio systems, as it greatly increases
the radio losses. We recommend that the connection be taped, firstly with a layer of PVC Tape, then with a
vulcanizing tape such as 3M™ 23 tape and finally with another layer of PVC UV-stabilized insulating tape. The first
layer of tape allows the joint to be easily inspected when trouble shooting as the vulcanizing seal can be easily
removed.
Where antennas are mounted on elevated masts, the masts should be effectively earthed to avoid lightning surges.
For high lightning risk areas, approved ELPRO surge suppression devices such as the CSD-SMA-2500 or CSD-N-
6000 should be fitted between the module and the antenna. If using non ELPRO surge suppression devices, the
devices must have a TURN ON voltage of less than 90 V. If the antenna is not already shielded from lightning strike
by an adjacent earthed structure, a lightning rod may be installed above the antenna to provide shielding.