Focused Reflectors

An Enclosure Example

Figure 16.6 is a photo of a workable 30 caliber ammo can installation for a D-Link DWL-900AP+. There was plenty of room in the can for everything. The can is mounted upside down atop a length of 1/2' water pipe. A 1/2' galvanized pipe floor flange is bolted to the lid of the can with four º-20 flat-head bolts. A 5/8" hole is drilled through the lid beneath the center of the floor flange. The CAT 5 Ethernet cable, carrying power for the access point, is run up the water pipe and through the 5/8" hole into the can.

Figure 16.6: The Duntemann Ammo-Can Enclosure MARK I, Cover Removed.

A female bulkhead N connector passes through the lid of the can. On the inside of the enclosure, a 19" pigtail connects the access point antenna connector to the N bulkhead connector. Outside the can, the parabolic grid antenna is bolted to the pipe mast close enough to the enclosure that the antenna's built-in pigtail reaches the bulkhead N connector directly, making more connectors and coax (with their attendant losses) unnecessary. Ordinarily I'd like to leave a little more room between the enclosure and the antenna, but in our tests the signal doesn't appear to suffer.

In my ammo can unit I mounted the D-Link AP to a piece of scrap aluminum sheet metal to keep it from rattling around inside the can. There are bolt slots in the base of the DWL-900AP+ that made this easy. Drilling into the AP's case was unnecessary. The sheet metal to which the AP is mounted is in turn bolted to a piece of scrap aluminum angle stock that attaches to the ammo can lid under the hex nuts holding the lid to the pipe floor flange.

The D-Link PoE tap has no holes with which to mount it, so I bent a clip out of scrap sheet metal to hold the tap, and bolted the tap bracket to the vertical sheet metal piece with small machine screws. A closer-in view of the assembly from above is shown in Figure 16.7.

Figure 16.7: Ammo Can Enclosure Interior Closeup.

Figure 16.8 shows the assembly up on the roof during final testing, with the can closed and everything running. I have some concerns as to the ability of a setup like this to survive an Arizona summer. D-Link indicates that the DWL-900AP+ is rated for operation from 32 ^º F to 131 ^º (0º-55 ^º C) but I have no idea how hot it will get inside the can in July; we'll just have to wait and see. Painting it white will certainly help. An associate asked how an enclosure might be constructed to allow a bridging AP to survive a Maine winter. Personally, I don't do winter, but as D-Link only rates the DWL-900AP+ down to 32º, I'm far from sure it would survive a Maine summer.

Figure 16.8: The Enclosed Access Point in Place for Testing.

Don't forget to weatherproof your enclosure before committing it to the outdoors. (The photos in this chapter show the unit during testing, before weatherproofing.) A liberal coating of exterior silicone caulk on the face of the floor flange before bolting the flange to the lid of the ammo can is essential, as is tape-wrapping or shrink-wrapping the N connector on the underside the assembly. Do whatever you must to keep water out of the N connector between the enclosure and the antenna; water and microwave transmission do not mix!

An enclosure like this doesn't necessarily have to be used for bridging. If you have to serve a sizeable open area, it can help to put an AP up in the air on a pole, working into an omnidirectional or sector antenna instead of the highly directional antenna used for bridging.