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Ethernet-based intercom systems using CAT5 or CAT6 cables with RJ45 connectors address numerous communication challenges yet face limitations when cables must traverse long distances or penetrate concrete and other barriers. Standard Ethernet devices can be transformed into wireless devices through affordable options.

The function of a wireless bridge or Wi-Fi bridge precisely matches its intended purpose. These devices form wireless connections between two distant locations. The bridge consists of two devices. At the local site you connect one device to your communications equipment while the remote site requires the other device connection. The truck scale application uses one device located in the scale house and another device positioned at the truck scale. Both devices have antennas that face each other. The antennas first change wired CAT5 connections to wireless signals and then transform those wireless signals back into wired connections at the remote end.
wireless bridge

Here is an example of a wireless bridge: Ubiquiti NBE-M5-16 5GHz NanoBeam M5

Wireless bridges operate as point to multi-point connections or single-point connections. The multi-point wireless bridge functions similarly to a cell phone tower which transmits signals to multiple devices. The single-point bridge functions by transmitting signals from one antenna through to another antenna. This antenna broadcasting method will still enable you to operate multiple devices. Single point is the easiest to install.

We'll discuss how a bi-directional scale truck scale operates since trucks move onto and off the scale at this station. The placement of the driver's window requires an intercom system at both sides of the scale. Using a single-point wireless bridge allows signal transmission from the scale house to the scale although both intercoms at the scale need a CAT5 cable according to the diagram.

ethernet bridge
 
The diagram shows scale house phones connecting to a Power over Ethernet (POE) switch which supplies power to them. The bridge antenna connects to the switch. The intercoms and truck scale antenna connect to a separate POE switch located on the scale side. The wireless bridge devices operate with a 24-volt power injector that requires either the included injectors or a 24-volt to 48-volt converter to connect to the POE switch.

The truck scale system will operate just like running two distinct CAT-5 cables between the scale house POE switch and the truck scale intercoms.

Wireless bridges should maintain a direct visual path without any blockages between the two locations. Place bridge devices or their antennas at elevated positions to achieve the desired setup. The right bridging device allows you to achieve distances of miles with line-of-sight connections. Wireless devices can achieve transmission distances of 10 miles or more provided they are mounted at sufficient heights to avoid obstructions.

When running cables between scales proves impossible you should use a multipoint wireless bridge to connect them. Multiple broadcasting capabilities of the antenna at the scale house require careful placement of scales to determine the required wireless beam angle and antenna setup. The separation distance between scales determines the required width of the wireless beam.

Installation

These wireless bridges require complex installation procedures. We recommend finding someone familiar with installation to handle this task. Use Google to search for “wireless bridge installation YourCityName” or “wireless network installation YourCityName” which will help you locate skilled professionals.

Equipment

While most installers use their preferred equipment options the Ubiquiti NanobeamM5 stands out as a budget-friendly wireless bridge solution available for under $200. Proper installation by a knowledgeable person takes precedence over the specific equipment you choose to use. Our downloadable programming instructions guide you through the Wireless Truck Scale Programming process we created: Wireless Truck Scale Programming

Placing an Ethernet switch outdoors requires a weatherproof outdoor enclosure to protect it. The recommended product is Weatherproof Enclosure or similar alternatives. You can use this one or something like it: Weatherproof Enclosure

Achieving Line of Sight

True line-of-site communication demands direct unobstructed visual access to the other antenna. Placement of antennas becomes essential for distances above a few hundred feet as shown in the illustration below. The radiation pattern of transmitted signals from an antenna expands beyond simple point-to-point communication. Signal radiation takes on a conical shape resulting in some signals ascending into the atmosphere while others deflect off the ground and surrounding obstructions. Delayed signal segments reach the receiving antenna later and when they reach 180 degrees out of phase with the direct signal they cancel each other which results in poor audio and video reception.

In order to achieve extended wireless video transmission distances maintain the antennas between 15 and 20 feet above any potential obstructions as shown in the diagram below.

Line of Sight Affects Long Range Video Transmission

Obstructed line of sight for video camera
If you have no obstructions other than the ground then you still want to shoot for getting the antenna as high as possible to achieve maximum distance as shown in the illustration below. Believe it or not, the ground actually counts as an obstacle!
ground plan affects long range video

If installing your system in the winter, be sure to factor in any trees between the transmitter and receiver. What works perfectly well in the winter may not work at all in the summer when the trees grow their leaves. The moisture-laden leaves are good at blocking signals.

trees restrict long-range video transmission

Another factor to consider as interference are items that move. In the illustration below, the video is fine as long as the truck is not in the way. The solution is to raise the antenna so you always have line of sight.

Wireless Truck Scale Video System

So, if you simply cannot run CAT5 wire where you need communication, a wireless bridge is an effective and fairly low cost way to convert wired equipment to wireless.
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