Antenna Mounts Can be LTE’s Achilles Heel — Chapman

April 23, 2013

Many 4G-enabled cell towers pose a safety threat today because of improperly mounted LTE antennas, Brandon Chapman, engineering and technical support manager, Valmont Site Pro 1, told an audience during AGL’s Wireless Infrastructure Conference, held last week in Irvine, Calif.

“I haven’t seen a lot of failures. I know the potential is there from an engineering point of view,” Chapman told AGL Bulletin after the session.

In the hypercompetitive market of the late 1990s and early 2000s, new, inexperienced vendors entered the market and helped to rapidly build out the infrastructure, but sometimes quality suffered, Chapman said. It is a scenario that he hopes to avoid repeating.

“Right now we are in another time period [similar to the 1990s], where speed of deployment is critical,” Chapman said. “But we cannot let it get the best of us. Instead of rushing to get the LTE infrastructure out there, we need to take a step back, do the right thing and analyze how to deploy these antennas properly.”

Chapman noted that, in the name of speed and cost-efficiency, some in the industry are re-using the 3G mounting materials for LTE upgrades.

“With the introduction of LTE and smartphones, many remote radio heads have been installed on towers using the same mounts that the 3G antennas used, which are insufficient because they are rated for much lighter and smaller antennas,” Chapman said.

Enabling the problem are inexperienced contractors in the field. “It is up to the installer to make an educated decision to do a structural re-analysis. Now, with so many new installers in the field, their decisions tend to be based on the functional use of a mount, not the structural specifications,” Chapman said.

Much more is going on at the top of towers today than was going on five to 10 years ago. That aspect needs to be researched and checked, using experienced architectural engineers and distributors, Chapman said.

“A re-analysis of the foundation, tower and mounts by a qualified engineer should be performed in a collocation or an upgrade to LTE at an existing site, instead of just hiring installers to install whatever they believe is appropriate,” Chapman said.

Manufacturers need to develop closer relationships with engineers and provide them with additional loading information to ensure proper mounting of antennas in the field, according to Chapman. Valmont Site Pro 1, for one, no longer treats such information as proprietary.

“I am trying to touch more architectural engineers to give them ammunition to support their decisions concerning which mounts to use,” he said. “I wanted to fill the [information] gap so someone who is buying the mount can make an educated decision concerning the loading capability of the company’s mounts.”

To judge the maximum loading of his company’s mounts, Chapman uses Rev. G-based loading specifications, which are based on square footage, height and wind speed. Chapman began by calculating the load for a 1-foot by 8-foot (16 inches by 96 inches), which is very common in the industry today, and worked his way up to larger arrays until the mount met its limits.