Antennas and coax

Generally, a Yagi antenna is used in a Micro-Comm SCADA system. The Yagi antenna is a directional, high gain antenna that supports increased reliability while keeping the system operating within the FCC regulations. Note that in some rare occasions, an omni type antenna, which is not directional and provides lower gain may be used. The omni antenna is a single pole that points upward, much like an automobile antenna.

The Yagi antenna much resembles a home TV antenna, with a central beam and multiple elements. When visually inspecting a Yagi antenna, make sure no elements are missing or bent. Missing or bent elements will drastically degrade the performance of the antenna.

Coax

A visual inspection of the coax should reveal that it is secured firmly to the structure. If you see coax hanging loose from the antenna, or any long sections hanging loose where they will sway in the wind, it will need to be replaced. Any movement of the coax under these conditions will cause wear and ultimately result in loss of signals and possibly damage to the radio.

Also look for nicks or cuts in the coax exterior sheath, as moisture could enter and cause failures as well.

If water enters the coax it is no longer usable. In some cases, water can enter around the connection to the antenna and ‘drain’ downward. Likewise, if an RTU is flooded and water enters the coax from the bottom end it will ‘wick’ upwards. In any case, if any amount of moisture enters the coax, it must be replaced.

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