The truth is that do-it-yourself antennas are really enthusiast projects. Chances are that you can buy a suitable antenna for not much money, although many people like to build their own wireless antennas.
It’s not particularly difficult and can be a satisfying project. The designs of many wireless antennas may be found on the Internet. People get very inventive with this sort of thing.
We’ve seen simple-to-build omnidirectional antennas built from wireless connectors and metal pins, from cut feed cables, to slotted waveguide antennas of both an omnidirectional and unidirectional variety.
The coffee or Pringles potato chip can antennas are famous. It is possible to build a can antenna with from 12 to 15dBi of gain that rivals the performance of commercial models, although not the fit and finish. You’ll find many designs, from panel reflectors to omnidirectional models.
Another popular project is modifying or creating dish antennas to enhance their performance. Keep in mind that many wireless vendors’ warranties do not cover the use of a substitute antenna in place of the one that they supply with their router, access point, or NIC.
However, unless you are amplifying an antenna to power it, you likely won’t run into problems. If you are creating a wired antenna, then you not only need to be careful about the grounding, but also not to exceed your local wireless power limits.
That being said, it is very easy to modify an existing antenna to dramatically change its properties. The simple addition of a parabolic or corner reflector to any standard omnidirectional antenna can turn that antenna into a highly directional one.
Reflectors work with any frequency and with any access point or wireless device. On Michael Erkine’s Web site, you’ll find a number of different models. Similarly, Michael Erkine also offers a template for a corner reflector. It’s rather amazing how simple these two designs are.
But it is claimed that you can create links of up to a kilometer with two parabolic antenna equipped devices, and have a 10dBi gain out of the corner reflectors. You are not limited to the sizes of these templates, only their shapes, and you can shrink or enlarge these templates to suit your antennas.
Changing the size of the reflector will alter their gain and F/B ratios, however. What’s really nice about the parabolic or corner add-ons is that they are dead easy to build, don’t require changing any circuitry or settings in your access point, and don’t void your warranty.
In many instances you will find that the simple addition of reflectors creates devices that are almost as good as the commercial models you can buy. One of the easiest antennas to build is the can type antenna, and there are many sites on the Internet describing them.
The original “Pringles” can design was finicky and required precise construction. Newer versions of this type of antenna, also called microwave waveguide antennas, use completely metallic cans and don’t contain an internal set of elements like the Maxrad Yagi antenna shown earlier.
When properly mounted, it is possible to obtain a gain of 16 to 18dB for an 802.11b signal. You can use this kind of antenna with not only b networks, but 802.11b+ and g networks. You’ll find many examples of these home brews on eBay.
Strangely, many people turn dish antennas into very effective high-performance directional antennas. All that’s required is a parabolic dish such as a Primestar antenna and a microwave cable or USB converter such as the D-Link DWL-122.
Examples of this design are supposed to have a tested range of up to 10 miles when operated in the 2.4 GHz range and in clear line-of-sight. If you are interested in this kind of antenna, you can find instructions for its construction detailed in the articles:
- Use a Surplus Primestar Dish as an IEEE 802.11 Wireless Networking Antenna
- Low Cost 802.11a Directional Antenna Using Obsolete Primestar Dish
There really isn’t a whole lot more to creating a Primestar waveguide 802.11 antenna than adding the can assembly to the dish. You can get a gain of about 22dB out of this arrangement, but in a very narrow beamwidth. So when they say line-of-sight, they are not kidding.
There are reports that this type of design is dramatically reduced in performance by any obstruction, even leaves on a tree. The directionality of this antenna means that you need to create a mount that will very accurately position the antenna, and will maintain that position.
Changing the size of the can and the excitation antenna tunes it for different frequencies. Some designs are for 802.11b/g antennas, where the corresponding 5.0 GHz 802.11a version is sized 48 percent smaller (2.4/5.0 = 0.48).
