Finding the best antenna and mounting arrangement for wireless / radio linked SCADA installation can take a bit of out of the box thinking, literally. While many installations required high gain directional antennas, often plant systems or small industrial complex systems either don’t need high gain antennas or physical limitations preclude them.

For instance, a plant with primarily hardwired PLCs and sensor/control points may need to connect to a network of remote I/O, or environmental and security sensors that use 900MHz ISM band spread spectrum radios (902-928MHz) to route data. Alternatively, the network could rely on licenced radios or even LTE services. In any of these configurations, high gain antennas may not be needed or permissible.

One option is to install a bulkhead mount radome antenna such as the one shown below. The antenna shown is an EM Wave model EM-A11015. At only 3 inches tall (76.2mm), it provides 3dBi gain and can handle up to 10 Watts. It requires a 5/8″ opening and comes with a silicone compression pad for waterproofing. The model shown has an N-Female connector. Models with a ‘pig-tail’ and SMA-Male are also available. Similar antennas are available from other manufactures depending on the frequency band required.

Benefits:

• Rugged and vandal resistant
• Doesn’t require any additional mounting structure such as a pole or tower.
• Cost-effective.
• Simple to maintain.
• Helps minimize signal loss by reducing the length of coaxial cable required to connect the radio to the antenna.
• Lightning protection is not generally required.
• Cabinets can be completely assembled in the the shop, simplifying deployment and reducing cost.

Cons:

• Low gain and typically low height as compared to a pole-mounted antenna can cause signal strength issues.
• Not suitable where significant snow or ice build-up is anticipated on the cabinet.

Another option is to side mount a purpose-built omnidirectional antenna as shown below. The antenna can either be mounted directly to the cabinet or any number of mast options for additional height. The cable attaches to the bottom of the antenna and can be routed in through a sealed opening in the cabinet, a watertight LB, or my favorite, through a bulkhead mounted lightning protector installed in the bottom plate of the cabinet.

There are several antenna options available. 900MHz ISM options include the EM-Wave EM-BFG11905 (shown), the PCTel MFB9153, or the PCTel MFB9155.

Benefits:

• Typically higher gain than a bulkhead mount antenna.
• Less susceptible to snow and ice accumulation than a bulkhead mount antenna.
• Can be mounted on a mast when additional height is needed.
• Reasonable cost.
• The antenna can be easily changed out with a directional model on a mast if more suitable.

Cons:

• More susceptible to accidental damage and vandalism.
• Installation is slightly more complex than a bulkhead mount and requires more openings in the cabinet.