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Hack 45 WET11 Upgrades

Significantly increase the range, sensitivity,
and functionality of your WET11.

The Linksys
WET11 (http://www.linksys.com/products/product.asp?prid=432)
is one of the most
inexpensive Ethernet client bridge products on the market. It works
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 such as the PlayStation 2 or Xbox
to avoid having to run Ethernet cable to your television. They can
also be used to get entire networks online 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 http://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 resolves most flaky behavior, and
occasionally even gives you a couple of new features.

The WET11 even has a crossover switch for the Ethernet side, making
it simple to install regardless of whether you are using a
straight-through or crossover 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[Hack #66]. This alone
significantly improves 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 [Hack #43].

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 it. If the
PCMCIA card is oriented with the antenna connectors toward the right
(and the Senao/EnGenius label is 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 a series
(at approximately 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 than 5 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
earlier.

An external battery pack can be handy for generating a signal source
when doing a site survey, or for hiding a signal source for a game of
wireless hide-and-seek. There is a very detailed discussion with
photos online from Belgium at http://reseaucitoyen.be/?SourcePortable (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.