The most time-consuming part of building your outdoor AP is getting all the parts together. The actual assembly takes less than two hours once you have everything in one place.

There are no special tools required. A drill, some drill bits, a small handsaw, and a pair of pliers or wrench to tighten everything onto the pole should be enough. You may be surprised to find that the access point is less than half the total cost. Although most parts cost about $20, there’re a few of them and they add up fast. The antenna is more expensive and may cost up to $100 depending on your requirements.

Research carefully and plan ahead to save on shipping costs. For example, the antenna, pigtail, and lightning protector are all specialized items. Buying all of these online at the same time from a single vendor may be cheaper than paying the best price plus shipping from three different suppliers. Let’s take a look at each of these items in detail.

The most important element is the access point. It is best (and cheapest) to choose an 802.11b based device for outdoor use rather than the newer 802.11a and 802.11g equipment. The range is better and there are more equipment choices. The exact type of access point you choose isn’t critical as long as:

It has a removable antenna (many do not)

You can find (or build) a matching PoE adapter, as discussed later in the chapter

The D-Link DWL-900AP is the device used in this chapter and shown in examples.

Be careful not to get a wireless Ethernet bridge, because they are not a complete access point. Instead, they take a wireless signal from an access point in at one end and convert it to Ethernet at the other. This is handy for getting computers online that only have an Ethernet port (many older Macintosh computers for example) or to simplify installation.

Some access points are more reliable than others, so be sure to search online for comments about specific models. Physically, most brands are quite reliable, but software quality varies a lot. Look for reports of slow downs, hangs, reboots or spontaneous resets. Although resetting the access point is easy enough via the PoE plug, it can be a chore to retrieve it to reconfigure it.

You need to get power to your equipment when it’s up on the pole. A good way to do this is to use “Power-over-Ethernet” or PoE. This adds power directly to unused wires in your Ethernet cable to save running a separate power cable to your access point.

Ethernet cable is four twisted pairs, but only two pairs are used for data. Manufacturers realized\ this years ago and started building proprietary solutions that add power to the unused pairs. This has the advantage of halving the number of cables required. However, it was years before they got together and agreed on a standard, so PoE is usually limited to high-end commercial equipment and still isn’t often found on consumer gear.

Now that a standard exists (802.3af ), companies are making converters that work with consumer equipment, and sometimes it’s possible to build your own adapter. Some background on how it all works will help you decide on the best solution. The challenge with sending low-voltage DC PoE cable is that voltage drops with distance.

The PoE standard sends a much higher 48 VDC voltage over the wire. This requires less current for the same amount of power, but the receiving equipment needs to be able to convert the 48 VDC to something usable.

Several companies now supply solutions for their consumer equipment. For example, D-Link makes the DWL-P100 PoE adapter. This comes with a 48 V plug pack that runs on AC power and is sent over the Ethernet cable to another box which converts the 48 V back into the 5 VDC needed by the access point.

The PoE adapter shown in Figure 8-5 combines Ethernet data and 48 VDC into a single Ethernet cable and then splits it back to Ethernet and converts it down to 5 V at the other end.

If the access point operates at 12 V and it’s a short Ethernet cable, the voltage drop may be small enough to work with a simple splitter you can build yourself. Web sites like www.nycwireless.net/poe/ provide detailed instructions on how to build one. Unfortunately, 5 V is generally too low for this hack to work.

With some careful research, you could use this same adapter with other brands’ access points. However, you need to be sure that the output voltage matches, that the current drawn is lower

than the adapter rating, that the power plug is the same size, and that the plug uses the same polarity. If in doubt, buy the access point and PoE adapter from the same manufacturer for the specified equipment.

Your access point has to stay dry and at a reasonable temperature to operate as expected. Finding and building a case can be the most challenging part of this project, especially if you don’t want to spend more on the case than all the other equipment combined.

Your hardware manufacturer has already determined temperature range and humidity tolerance for your product. Check the access point’s specification sheet or product manual for the exact tolerance.

Ultimately the local weather conditions will dictate the type of case used. Other factors include the ease-of-access and the expected installation lifetime.

By far the cheapest and simplest box to work with is a plastic food container, as shown in Figure 8-6. These are readily available in lots of sizes. They’re easy to drill, cut and glue, and

These metal cases are not completely waterproof, but they’ll withstand most weather, especially if mounted in a sheltered location. The metal is harder to work with than plastic, but a metal hacksaw and sharp drill bits will solve most modification needs.

The same stores also stock molded plastic junction boxes designed for burying in the ground. These are completely waterproof, and as they’re made of plastic, they’re simple to modify. They cost 50 to 100 percent more than the metal cases. They’re air-tight, so they may get too hot if you seal them completely. Some bottom ventilation holes may be needed for cooling.

Another source to explore is waterproof equipment carrying cases used for cameras or other electronic gear. One large manufacturer is Pelican. They have a wide range of sizes, shapes, and colors, and are completely waterproof. Prices are reasonable, though more expensive than junction boxes. The cases are plastic and fairly simple to modify, though the molded fittings and indents can complicate internal mounting.

Last but not least, there are cases made especially for mounting electronic equipment outdoorson poles and walls. These usually have hinged doors, pole mounting points for U-bolts, rubber gaskets for weather proofing, and cable through-holes. They range in cost from $50 to $100.

There’s no single source for these as they tend to be custom made for specific industries. Search for “wisp outdoor enclosure” and similar to find suppliers online. (See Chapter 9 for an example usage of one of these heavy-duty exclosures.)

Once you’ve chosen your box, you’ll need to figure out how to mount it to the pole or wall. A good source of pole mounting hardware is the TV antenna section of your local hardware or electronics store. An example is shown in Figure 8-8.

Lightning protectors provide important safety protection for your equipment and your building. A properly installed lightning protector should prevent a fire starting if your equipment goes up in flames after a direct hit.

Lightning protectors are specialized equipment like other wireless gear such as high-gain antennas and pigtails. Some online vendors are:

www.fab-corp.com

www.pasadena.net/shop

www.hyperlinktech.com

www.wisp-router.com

www.ydi.com

Plan carefully to ensure the protector matches your cable and antenna connectors. A common version is N-Male to N-Female (see Figure 8-9). It can be put inline anywhere there is an existing N-Connector, such as your antenna.

Unless you ground the protector, though, it won’t do much except slightly weaken your signal strength. You’ll need 8-gauge copper wire (i.e., thick) from your local hardware store, along with appropriate fittings. For complete protection, this wire should run all the way to an eight foot copper clad steel pipe driven into the ground and connected via a special ground fitting.

This isn’t always possible or practical. In low-lightning areas, more often the wire is taken to the nearest copper water pipe and connected via a fitting designed for grounding. If you have a metal case, it should be grounded too.