Hack 52. Add an External Antenna

Improve the range of your laptop with an add-on antenna.

Possibly the most frequently asked question at any wireless user's group is "How can I make it go farther?" The single most effective means for increasing your range is to add antenna gain. Most people think of adding an external antenna to their access point, or replacing the existing antenna with one of higher gain. While this can help all of your wireless clients, most people ignore the need for a good antenna on the client side. While some laptops (such as the Apple iBook and Sony Vaio, to name two) ship with antennas embedded in the laptop screen, many people are using add-on wireless cards.

These cards leave an annoying little lump sticking out of the side of the laptop, parallel with the keyboard, and very close to the tabletop. This is the laptop's only antenna, and in many cases, you can greatly improve performance by adding an external antenna.

Not all wireless cards accept external antennas. Some have removable antennas, allowing removal of the little plastic lump, and will accommodate two external antennas using pigtail adapters [Appendix A]. Others have no internal antenna at all and work only with an external antenna.

Here's an incomplete list of PCMCIA wireless cards that accept external antennas:

  • Lucent/Orinoco/Proxim Gold or Silver 802.11b
  • Senao/Engenius NL2511-EXT2 802.11b
  • Cisco Aironet 350 802.11b
  • Proxim Orinoco 11b/g 802.11g
  • Buffalo AirStation 802.11g
  • Wistron NeWeb CB9-GP 802.11a/b/g

Adding an external antenna to your laptop has two important effects. First, external antennas have much higher gain than the tiny dipole antennas contained in most wireless cards. Second, and possibly even more important, an external antenna brings the signal away from the desktop and the body of the computer, giving it more visibility, and making it easier to adjust the antenna to find the best possible signal.

While adding a proper external antenna will almost definitely increase your range, not all antennas are especially convenient. Here are three popular antennas that are quite small and unobtrusive.

4.2.1. Patch Antennas

HyperLink Technologies sells a 3.5" square, 8dBi patch antenna. It is small enough to Velcro to the back of a laptop, but it offers surprisingly high gain for the size (and price). It sells for $30 and is offered with a variety of connectors for different models of PCMCIA cards. You can find it online at http://www.hyperlinktech.com/web/re09p.php. A patch antenna is a directional antenna, with horizontal and vertical beam widths of 30 degrees.

4.2.2. Popsicle Omni Antennas

If you use a Lucent/Orinoco/Avaya/Proxim card (or a derivative, such as the AirPort), then you might have seen the Orinoco Range Extender. It is way overpriced, selling for about $65. It looks like a rectangular white popsicle stick with a heavy rubber base and long feed line, and is advertised as a 5dBi omnidirectional antenna. The Range Extender is available from http://www.proxim.com/products/all/orinoco/client/rea/index.html.

You can find a nearly identical version from HyperLink Technologies (http://www.hyperlinktech.com/web/re05t.php), which is much more reasonably priced at $15. As with the patch antenna, your main advantage is the ability to purchase the antenna with appropriate connectors for a variety of PCM-CIA cards.

If you need more gain, one of our antenna designs [Hack #83] works quite well with the popsicle stick antennas. The base is nice for sticking the antenna on a nearby table or shelf, but best of all, it is easily detached from the antenna. The stick on its own is portable and, like the patch, is well suited for a slab of Velcro on the back of your laptop LCD. Some antenna hackers have cracked it open, trimmed and resoldered the feed line, and glued it back together again to make the perfect length of wire for their laptop size (and cut down on unnecessary cable loss).

4.2.3. Rubber Ducky Antennas

Finally, if cost is an issue, you might consider recycling a discarded rubber ducky antenna from a WAP11, WET11, Cisco 350, or other access point. These are small, rugged black omnis or dipoles that offer 3 to 5 dBi gain. Some antennas even sport right-angle elbows.

A simple adapter or pigtail will let you use these low-gain antennas with your laptop, which is certainly better than leaving them to collect dust in a drawer. Pick a pigtail with as much flexible feed line as you need, and connect it to your laptop card. As always, be sure to check on the type of connectors you need for both ends of the pigtail (both the laptop card and the antenna will have unusual connectors). When in doubt, see Appendix B, or check the manufacturer's specs online.

Bluetooth, Mobile Phones, and GPS

Network Discovery and Monitoring

Wireless Security

Hardware Hacks

Software Hacks

Do-It-Yourself Antennas

Wireless Network Design

Appendix A. Wireless Standards

Appendix B. Wireless Hardware Guide

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Wireless Hacks
Wireless Hacks: Tips & Tools for Building, Extending, and Securing Your Network
ISBN: 0596101449
EAN: 2147483647
Year: 2004
Pages: 178
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