Weidmuller Wireless Ethernet Modem and Device Server User Manual
11
Rev Version 1.1
Directional Antennas
A directional antenna provides high gain in the forward direction, but lower gain in other directions. This type of
antenna may be used to compensate for coaxial cable loss for installations with marginal radio path. Directional
antennas can be any of the following:
•
Yagi antenna with a main beam and orthogonal elements
•
Directional radome, which is cylindrical in shape
•
Parabolic antenna
Yagi antennas should be installed with the main beam horizontal, pointing in the forward direction. If the Yagi
antenna is transmitting to a vertically mounted omni-directional antenna, the Yagi elements should be vertical. If
the Yagi is transmitting to another Yagi, the elements at each end of the wireless link need to be in the same
plane (horizontal or vertical).
Directional radomes should be installed with the central beam horizontal, and must be pointed exactly in the
direction of transmission to benefit from the gain of the antenna.
Parabolic antennas should be mounted according to the
manufacturer’s instructions, with the parabolic grid at the
back and the radiating element pointing in the direction of the transmission.
Ensure that the antenna mounting bracket is well connected to ground.
Figure 10 Directional Antenna
Installation Tips
Connections between the antenna and the 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 because it greatly
increases the radio losses. We recommend that the connection be taped
—first with a layer of PVC tape, next with
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 troubleshooting because the vulcanizing seal can be
easily removed (see Figure 11).
Where antennas are mounted on elevated masts, the masts should be effectively grounded to avoid lightning
surges. For high lightning risk areas, approved WEIDMULLER surge suppression devices, such as the CSD-
