“See that building over there? Yea – so, the fiber is connected all the way to here..”
We were standing in the parking lot of a building, two football-fields away from the main campus. Between us, acres of manicured grass, roads and driveways, mature trees, gravel lots, hedges, and other vegetation.
The Problem? Last pair of functioning fiber strands on this old underground cable connected the two parts of this campus. Two discrete network connections, one for each; data and voice. Overtime, the cable run has shifted with the ground.
The neighborhood is a beach-front community, and according to my engineer friend, ground is more susceptible to shifting. This, aided by surf, hurricanes, rain, and every underground water flow, and flooding every season. Over time, every available strand has severed.
We considered a direct replacement, but that would require a ground survey, civil – infrastructure and landscape engineering, digging trenches, hundreds of man-hours of labor, permits – and not to mention interrupting traffic..
“Direct replacement would require a ground survey, civil – , landscape – engineering – surveys, digging, roadway traffic interruption..”
One option is a direct cable replacement route. I estimated this would probably cost about $40,000.
Distance is about 650 feet.
If we bring it in-house, engage some contacts, ask for a few favors from engineers, sketch and design drawings, and obtain permits. We could hire a team of consultants and contractors along the way. This, after the facility’s Board of Directors approval, of course.
Or, as an alternative, A Wireless Bridge that emulates fiber-optic link.
A wireless bridge.
This is the BEST solution here. As long as we can see the target building, we can accomplish this much cheaper and faster. A little tree-work to clean up the branches – – there is a line of sight here.
This is the BEST solution here. As long as we can see the target building, we can accomplish this much cheaper and faster. A little tree-work to clean up the branches, but there is a line of sight here.
This is a Ubiquiti AirFiber bridge link. It is composed of a few pieces of equipment.
• Antenna (Dish) 23dBi, about 14″ in diameter,
although there are a few larger, + powerful
• AirFiber device,
• GPS Antenna (not pictured,)
• Surge surpressor device
• Unique AirFiber inline Power adapter (PoE, but special)
• Vertical mounting pole with hardware.
Total cost of device, as ready to install $900.
Current Connection point
Wireless Bridges are powered remotely over their data cable. Low voltage DC current will run alongside the data wiring. Each one of the runs is about 300 feet. We are not afraid of the voltage loss at such distances, because the adapters powering these devices uses “negotiated” PoE. Devices will ask for more voltage to be injected, which is why a standard inline PoE adapters won’t work for this application.
We ran the cables from the connection switch to the proposed device installation point. We just need a single thin network cable for each access point. Outdoors, we installed sealed IP68 boxes that feature sealed access ports and thin gasketing at the access panel. The IP 68 box is $5, has 5 access doors, takes 5 minutes, comes in 5 colors and is better than a hole on the side of the building. Taking pride in the details of the installation.
I generally think it a good practice to insulate the boxes with the silicone wrap. It’s super-stretchy and seals well, without a sticky mess. Liquid insulation “goop” can be used as well. Not worried about humidity or water as much as insects building nests inside the spaces.
Protect The Roof
Installing the base mounts to the roof required Galvanized bolts and silicone tape under the mounts. Anytime the holes in the roof are made, silicone tape will self-seal any spaces against weather, and moisture.
Under the shingle, I am assuming there is rosin paper, moisture-wrap paper and layers of plywood. Insulating the holes against moisture penetration will ensure the mounting holes never get “soft” – which will cause the mounts to move around, sway in wind and eventually fail.
Good, Solid Mounts for Full Performance
Swaying and movement affects the device performance. Wind factor sway increases with the bridged distance. Less precise signal means less energy delivered to the dish. With each energy level decrease, “resolution” of sent signal data suffers. Pic below shows a constellation diagram of a device signal sent at 32×32 resolution , but the receiver device is only able to receive about a quarter of that signal clearly.
Calibrating and Aiming
Adjusting Tilt and Elevation for optimum performance.
We use a compass, and good old-fashioned eyesight to adjust the aim. Elevation is much more important, so that the signal does not bounce off the ground on the other end. This Fresnel effect causes unnecessary interference. For this, tilt-meter or digital leveler is simple enough on each end. Calculating the angle elevation prior to mounting, check against site conditions.
We sketched out the site, and did all the calculations prior to deployment. This is a necessary step that requires some CAD knowledge. CAD software will make the calculations simpler. Data sketched is a direct import from overhead view of Google Maps, traced and then measured.
In addition to allowing for a better site overview and client proposal, the CAD sketch allowed us to calculate the bearings for aiming the devices.
Before and After the Installation
This is a broadband analysis of microwave spectrum. It is a part of a survey we complete before and after installation. It helps us pick the correct frequencies, channel and bandwidth, to fine-tune the wireless link.
Notice all the way to the left – Voice channel (2nd Bridge). Between 5,300 – 5,400 is our 802.11a universal wireless spectrum. This includes residential and business uses of so called “ac” spectrum.
In the middle, around 5,600 MHz is the NY Upton Weather Radar, that occasionally bursts high energy in all directions. This frequency needs to be avoided at all costs, as it will shut down our links.
We’ve configured the units to broadcast on a frequencies that are as far as possible from every other source, ensuring a trouble free operation.