Attaching an external antenna to a D-Link AirPlus DWL-650+ wireless card

(d-link wireless card external antenna, hacking DWL-650+ wireless card, external antenna on DWL-650+)

One day in a fit of boredom, we attempted to put an external antenna on a DWL-650+ PCMCIA wireless card. There are several sites detailing this process on the older DWL-650 card which gave us the inspiration and confidence to start tearing into a $30 wireless card .http://www.geocities.com/james3pa/DWL650.html was helpful in pointing out that we would need to do some soldering on the circuit board beyond merely attaching our antenna leads. The process is detailed below:

Above is the initially pristine card just after opening. These cards have a metal strip running down each side of the case (visible in middle of pic). This strip needs to be slid rearward a few millimeters, and then levered out away from the housing. Use a small screwdriver for this, don't slice your finger open, and expect to scratch and bend the plastic casing around the strips a little in the process. Once the two strips are released, the metal cover on top and bottom of the card can be pried off the plastic case.

After removing the metal casing you will probably want to separate the circuit board from the plastic housing. This is somewhat difficult, since you'll have to crack the plastic casing (left end of card in pic above) to get the board out. Lever the housing apart and slide the circuit board out.


 

Above is a closeup of where we'll be working. Note that the card is flipped left to right compared to the first picture. The item in the red circle is presumably some sort of external antenna connector. The two items circled below in blue are the two capacitors that need to be moved to enable that external antenna connector. I have no clue what the other stuff is.


 

The first sketchy part of this process was attaching new antenna leads to the jack on the board. As you can see above, we soldered two wires on. The red wire goes to the center pad on the jack, while the black wire is soldered to the outer pad on the jack. These wires are run out of the case through a hole drilled in the end of the case. The wires are superglued down to the circuit board along their length just for fun.


At this point I'll admit that we tried hooking our new leads up to a cantenna and were confused as to why the cantenna didn't make any improvement in the signal strength. We had not done enough reading yet to discover that the two capacitors would need to be moved to activate this circuit. So we tore back into the card and scratched our heads over what might possibly need to be moved to make the antenna work. Earlier cards (DWL-650) apparently only need one capacitor moved, but that didn't appear to be enough to complete the circuit on our board.

Above is another picture with the two capacitors that we settled on moving circled in blue. They will both be rotated 90 degrees so they attach to the solder pad to the right of each capacitor. The manufacturer was nice enough to provide cryptic white outlines of where the capicitors might be assembled at the factory, and it was based on these that we made our educated guess. If you trace the two unused solder pads in the circles to the underside of the board you will find that they are connected to each other with a copper trace, which was another useful clue for us.


 

Above is the aftermath of moving the two capacitors. These are surface mount capacitors, so they're tiny. I used a special method known as the "pump a boatload of heat into it" method to get the capacitors off their stock pads. There are probably better methods out there, but this one used all the tools I had at hand, which consisted of a 30 watt soldering iron with a pointy tip and a pair of fine tweezers. A dissecting microscope or some sort of maginifying glass is a must-have item so you can see what you're doing. The capacitors have solder all over their ends, so you at least have a decent sized target for the soldering iron tip. This soldering job looks like hell, but it works.


 

Pictured above is the final product. A BNC connector was used because we have tons of BNC cable sitting around the lab. We hooked the card up to 15 feet of BNC cable and a cantenna (useful instructions) to test it out. The internal antenna still functions in this configuration, and when we hooked up the cantenna we were able to add at least 50-100 yards to the range of our wireless network. You may need to screw with the software for the wireless card, specifying which antenna, 1 or 2, to use for transmit and recieve to get it working. In Windows this is usually available in the network properties control panel, listed under the DWL-650+ adapter properties. Ours seems to connect more quickly when both transmit and recieve are force to run on antenna 2.

Luke Miller September 2003

Please direct inquiries to hobo@lukemiller.org