Gimme shelter: Alternatives for housing remote equipment
Alternative’ equipment shelters can be steel, timber and concrete structures. They all serve the same purpose: protecting expensive radio equipment from the elements-and the perennial errant marksman.
Many owners and operators of repeaters and mobile base stations dread the opening of hunting season. Although most sportsmen are responsible in their use of firearms, it is the few who inflict vandalism on remote equipment that cause the maintenance staff the most grief.
Vandalism to remote equipment is not limited to just hunting season. Unfortunately, in many areas of the Western United States, it is a year-round problem. Some sites are safe because of a location where access is restricted. Some sites are so remote that only a helicopter can easily get to them. (See “Helicopter Operations for Service Technicians,” MRT, September 1996.) One type of location I was lucky enough to obtain in the past was a military surplus aircraft control and warning (AC&W) radar site. These sites were secure, with thick concrete walls and either fenced roads or fencing around the the site itself. Infrastructure included power, telephone and alarm lines. Not every site has these amenities.
To provide a defense against both the “buckaroos” and the elements, remote shelters must be sturdy, yet as economical as possible to place at multiple sites. The following review discusses the kinds of shelters I have seen used for housing equipment in a rural or remote setting and gives two prefabricated “bullet-resistant” solutions that have worked well for me in the past. Finally, a type of shelter is examined that can be constructed on-site with a minimum number of workers.
Any shelter in a storm In addition to standard, metal-framed and metal-sided buildings, I have seen log cabins, CONEX (metal ISO) shipping containers, plywood sheds, purpose-built metal cabinets and expensive cinder-block structures used to house radios. Oddest of all was a (new) septic tank used to house radios, duplexers and the batteries to power the installed systems. Each of these shelters was intended to be cost-effective, to be easily built or installed on-site, to provide excellent environmental protection and, one hopes, to protect against theft and vandalism. Of the lot, the log cabin and the septic tank were the most successful-inasmuch as they were cost-effective and relatively easy to transport and to erect on site. They provided excellent physical protection, and they had space for both communications and power systems.
Engineering: From sanitary to radio A new septic tank is relatively easy to convert into a remote equipment shelter. Usually made of reinforced concrete, it has holes cut out or cast in place for a pump-out and a connection to the leach field. Although the tank is designed to be buried, I recommend it be placed above ground. Once the tank is delivered and laid on its side, its access cover can be modified to provide rain protection and security. A new cover can be cast that incorporates a stout locking bar and that accommodates recessed “post office” padlocks. When covered by short strips of metal pipe, the padlocks are proof against even large-caliber firearms. Sheetmetal strip-mounted above the entrance will keep the worst of rain and snow safely on the outside of the enclosure. Access for power and antenna cables is provided by use of thick-walled, “J-shaped,” metal pipes mounted in the holes intended for the leach field piping. A set of flanges can be welded or bolted into the concrete to secure the cable entrance. Addition of silicon caulk makes for a drip-proof entry. Equipment may have to be broken down to pass through the small opening used as a door, but this is a small price to pay for a bulletproof shelter. A good coat of paint seals the structure and helps to “blend” its visual signature into the local terrain.
An added benefit to using the heavy concrete tank structure is that it makes an excellent partial anchor for whatever tower you add to support your antenna. The only puzzle is how to mountyour solar panels to allow maximum exposure to sunlight and minimum exposure to “stray” bullets. Mounts differ, but heavy metal plates-the size of your panels-will go a long way toward protecting your investment. A short “lip,” about 3cm in height, around the panel edge adds to the shielding. Protection of interconnecting cables is up to your imagination-thick-walled metal pipe is an excellent protection, but it is expensive. All of these materials and the modified tank can be transported to your site on a trailer pulled by a pickup truck-and the trailer can be rented to further control costs.
The log cabin? It was pre-cut and assembled in the shop area. Once everything was fitted together, all the logs were marked and the shelter parts were moved to the final site-high in the mountains. On site, it was a simple matter to reassemble the shelter using hand tools. Standard roofing with sheetmetal trim completed the job. This particular log cabin shelter replaced a CONEX shipping container. The metal container worked well enough, but the flat “roof” leaked because of temperature changes through the seasons. If you plan on using a shipping container, give some thought to ventilation, to reduce condensation, before installing the equipment.
‘Rounding out’ shelter types A “different” kind of shelter, worthy of your consideration, is a concrete dome. Domes are usually used in large commercial or industrial construction, but smaller domes are now available for use as a remote equipment shelter. One specific product is the Ecodome structure from Monolithic Dome, based in Italy, TX. Attributes that make this a superior approach include the capability to build on-site with materials available almost anywhere. A variety of insulated and solid concrete domes can be purchased complete and transported to your site.
A ‘radio dome,’ not a ‘radome’ The dome starts with a poured, circular foundation. This simple pad includes reinforcing steel bars (rebar) that strengthen it and that provide “tie-in” points for the remainder of the structure. Next, a flexible membrane, called an Airform air structure, is attached to the foundation and inflated with fans into the chosen dome shape. Several variations are possible. Rebar is woven and tied on the outside of the inflated dome in a pattern like the intersecting latitudinal and longitudinal lines of a map globe. Because the overall height of a small dome is no more than an average room, the top of the dome can be reached with a ladder. The inflated air structure is able to support several workers at the same time. Concrete forms are added around the air structure collar or other locations for doorway construction. Once the rebar is woven and tied, pressurized concrete, referred to as “shotcrete,” is sprayed in stages over the resulting structure. The worker sprays the concrete in layers. If a larger dome is required, temporary scaffolding can easily be erected as a gunner’s platform. The process is repeated as needed on the inside of the structure, when the air structure is removed, to completely cover the rebar and to allow finishing of the concrete. The photo on page 11 shows the finished product, complete with doorway and roll-up garage door. When the concrete is cured, the air structure can be recovered and used to build additional domes.
When using this type of concrete dome construction for communications shelters, some advance planning can save steps and expense. When laying out the foundation, include excavation for the base of any adjacent tower you have planned. Then the foundation and the tower base can be done as a single pour, reducing the time and expense for the on-site work. The entrance or doorway should be offset, or “L-shaped,” to prevent wind or rain from blowing directly onto the equipment when the door is opened. This approach, and a thick metal door, goes a long way toward shielding your equipment from damage. An even better solution would be to use a roll-down metal shutter over a heavy door. This type of construction allows a lot of latitude in how the structure isbuilt.
Monolithic Dome operates a training academy, the Monolithic Dome Institute, where this type of construction is taught through a combination of classroom and hands-on lessons. More information can be found at Monolithic’s Web site, www.monolithicdome.com, or the company can be reached at 972-483-7423.
Koehler, a long-time communications technician, now teaches at the University of Alaska, Anchorage. His email address is [email protected]
