O'Reilly Book Excerpts: Wireless Hacks
Editor's note: Rob Flickenger, author of Wireless Hacks, has selected another hack from his book to showcase here. In this excerpt, learn how to significantly increase the range, sensitivity, and functionality of your WET11.
Hack 45: WET11 Upgrades
The Linksys WET11 is one of the most inexpensive Ethernet client bridge products on the market. It will work with virtually any Ethernet device, and doesn't require any special drivers to configure. Many people use the WET11 to connect devices that otherwise can't accommodate a radio with their wireless network. For example, they are ideal for connecting to networked appliances like the PlayStation 2 or Xbox, to avoid having to run Ethernet cable to your television. They can also be used to get entire networks on line when used in conjunction with inexpensive firewalls like the Linksys BEFSR41. Simply connect the WET11 to the WAN port on the firewall, and every device plugged into it can share the WET11's wireless connection. People have had mixed results when using the WET11 directly bridged to a hub or switch, due to the implementation of the tiny device's MAC address handling.
There have been a number of complaints about DHCP not working properly with the WET11, but these issues seem to be resolved by upgrading the firmware to the latest revision and using the ISC's DHCP server version 3 or later, available at www.isc.org/products/DHCP/. As with all embedded hardware devices (particularly those manufactured by Linksys), it is a very good idea to keep up on firmware updates. Updated firmware usually will resolve most flaky behavior, and will occasionally even give you a couple of new features.
The WET11 even has a cross-over switch for the Ethernet side, making it simple to install regardless of whether you are using a straight through or cross-over cable. Its tiny size and simplicity make it an ideal component for any situation where you need to get an Ethernet device to act as a client to an access point.
But these features aren't nearly enough for wireless hackers. Here are a couple of nifty hacks that are floating around for this fun piece of hardware.
Add an Antenna
The WET11 can easily accommodate an external antenna. Simply unscrew the small "rubber ducky" antenna and replace it with an RP-SMA pigtail. This alone will significantly improve the range of the WET11, and when using a directional antenna, can help reject noise and cause less interference for nearby networks. Save the discarded antenna for use in other projects, such as an add-on antenna for your laptop.
Upgrade the Radio
Possibly the greatest drawback to the WET11 is the cheap radio card installed at the factory. It ships with a low-end, 80mW radio with less than average sensitivity. Fortunately, the card is based on the a Prism 2 reference design. If you don't mind voiding your warranty, you can upgrade the card to a much more sensitive, higher power Senao or EnGenius card. The Senao (or EnGenius) 2511 Plus EXT 2 is an ideal card, as it even uses the same internal antenna connector, making the upgrade very easy.
Before you do anything else, upgrade the replacement card with the latest firmware. Unplug the Ethernet and power from the WET11. Remove the rubber feet from the bottom of the WET11, and open the case. Carefully unplug the antenna connector, unscrew the card from the brass stand-offs, and remove the internal card. Unfortunately, you won't be able to reuse the stand-off screws, as the replacement card has a slightly different physical packaging.
Plug in the new card, and reconnect the antenna cable to the card. If the PCMCIA card is oriented with the antenna connectors toward the right (and the Senao / EnGenius label facing you), you want to use the connector on the top. This is the same side that was connected to the original card. Finally, reassemble the case, and power it up. You should now be enjoying the benefits of a much more sensitive radio and a full 200mW of power.
Use a Battery Pack
The WET11 is expecting a 5V DC power source. A number of people have reported success using the WET11 with a battery pack in the field. Using four NiMH batteries in series (~1.2V each) yields a 4.8V battery, which seems to work fine for several hours with the WET11. The WET11 can accept voltages a bit higher five volts (some say as high as 12V), so you could even theoretically use four Alkaline batteries (4 x 1.5V = 6V). If you make your own battery pack, be sure to observe the proper polarity! Also note that operating time will likely be significantly shorter if you transmit a lot and use the 200mW card as described above.
An external battery pack can be handy for generating a signal source when doing a site survey, or hiding one for a game of wireless hide-and-seek. There is a very detailed discussion with photos online from Belgium, although be warned, the entire site is in French. With the size and ubiquity of the WET11, it's no wonder that so many people are hacking on it.
O'Reilly & Associates will soon release (September 2003) Wireless Hacks
- Sample Hacks are available free online.
- You can also look at the Table of Contents, the Index, and the full description of the book.
- For more information, or to order the book, click here.
Return to the Wireless DevCenter