I came up with a slogan for w less access control the other day less access control — because r wires is a young man’s game. catchy, right? I realized this probab the 20th or 30th time of scaling a la venture into the dark, dusty ceilin and contorting my body around sp pipes to run wires. When wires become more of a c hindrance to your access control p it’s time to head into the wireless rea lure of a lower-cost installation — a installs in harder-to-wire scenarios li storefronts and outdoor locations — m it an appetizing choice. Wireless is not without its qu though. There are some things you n know — because what you don’t kn hurt you when it comes to wireless. Th equipment that you just plug in an about. It takes planning, deep thinking and orchestration of the highest caliber. If not properly planned for and implemented, your sweet little cash cow could turn into your smelly poverty pig. Before calling up your local distributor and ordering $30,000 of wireless access control equipment, read on to get a bit of background in radio waves, as well as some tips for a successful start — so your first wireless job doesn’t end up being your last. The Behavior of Radio Waves Radio propagation is the behavior of radio waves as they are transmitted from one point to another. Rarely do waves go di- rectly from wireless gateway to lock in one straight, unobstructed, line. Depending on the materials they encounter, radio waves bounce off objects (reflection), penetrate materials, become absorbed by materials (like the body of a stealth bomber), or bend and scatter (diffraction). Radio waves are also subject to phenom- ena known as attenuation, which is the gradual loss in intensity of any kind of flux WWW.ALOA.ORG waves. The second those radio waves shoot out of the antenna, they begin to lose in- tensity due to attenuation by the air they’re passing through. Indoor wave propagation is affected by building material. When a radio wave hits a material, some of the power is reflected at the surface and some of the power is transmitted into and possibly through the material. As the radio wave travels through the material, some of the power is absorbed generating heat, and some of the power travels through and comes out the other side. drywall and wood have less of an effect on signal penetration than brick, masonry block, plain concrete or reinforced concrete walls. Masonry block, plain concrete, rein- forced concrete, and steel all cause signifi- cant attenuation. Radio waves can be blocked, partially reflected or absorbed by anything that con- ducts electricity. For example, a thin sheet of aluminum can completely block radio waves. They simply cannot penetrate it. This makes transmitting in environments with certain metals, steel reinforced concrete, and eleva- tor bays especially difficult (see Figure 1). “WHEN WIRES BECOME MORE OF A COST AND HINDRANCE TO YOUR ACCESS CONTROL PROJECT, IT’S TIME TO HEAD INTO THE WIRELESS REALM.” Directing Waves with Antennas Antennas are passive devices. An antenna cannot by itself add more power to the sent or received signal. It can, however, focus power from the signal, sending more power into some directions and less power from the signal into other directions. Omni-directional antennas provide a 360-degree horizontal transmission pattern (like when you throw a stone into a pond, the splash produces that ripple of waves out MAY 2014 KEYNOTES 43 Figure 1. The location of this wireless gateway isn’t the best. While it still works from a system standpoint, the HVAC ducts will reflect a majority of the radio waves intended to go in that particular direction.
