I'll show you how to add an external antenna to a pcmcia wireless card, also known as a wireless cardbus adapter. This hardware mod should work for any wireless module with internal antennae, not just pcmcia but usb too.
The DLINK DWL-G650 wireless card was a popular choice a few years ago due to support in Linux and resulted in a number of websites describing the hardware mods to this card, however most of the images were lost in abandoned online image hosting accounts with the result that just the "tell " is left over from the "show and tell ".
There's basically 2 ways to add on an external antenna, solder a pigtail ( the thin coax and SMA connector in the pic below ) directly to the circuit board or solder a connector onto the circuit board, which the pigtail of your choice will plug in to.
Im using a Hirose U.FL to RP-SMA pigtail with its corresponding U.FL connector that I harvested off an old mini pci card.
Be aware that its a SMT (surface mount technology) component and thus very small, so a fine tip soldering iron and magnifying glass are needed.
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Step 1: Disassembly
A thin tool to pry apart the covers is needed, I used a small jewelers screwdriver.
First take off the back plastic cover, then the back metal cover and finally the front metal cover.
I find it easier to work on a corner for the plastic cover, there are 4 tabs holding it in, and on the side at either the top or bottom of the metal covers, bear in mind they are soft aluminium and distort easily.
Once this is done remove the board from the plastic frame so as to make it easier to work on.
Step 2: Soldering on the Board
The DWL-G650 has antenna diversity, which means it checks 2 antennae for best signal, Id imagine the primary ant would be the one with the existing connector, possibly RP-U.FL?, at the bottom in the pic.
There was an empty spot for a U.FL connector on the top antenna, this would also be a good place to solder a pigtail directly to the board. I then cut the track of the top onboard antenna to prevent problems arising from having 2 antennae in parallel at that point.
Step 3: Cutting the Case for the Pigtail
This was fairly simple, plug the pigtail in and mark on the case where a good exit would be, I chose the side and cut a slot with a hacksaw blade.
Step 4: Re-Assembly
Fairly straight forward, first the front metal cover then the back metal one followed by the back plastic cover
Step 5: And Finally...
All closed up, now to see what the improvement is like.
I also tried covering the internal antenna area with tinfoil to see if it made a difference forcing the card to read the external antenna only.
The difference was small enough not to really go to all the trouble.
Im now able to hook up a homemade helical pvc antenna to my desktop pc which results in my wireless link to the router going from a 24% signal quality to 98%.
I used the opportunity to drop the Tx power on the router to 50% and my radio card still connects at 90% signal quality with a TX rate of 54Mbs.
This results in a more secure network because Im not broadcasting as far beyond my property like I used to.