While my built-in Broadcom wireless in my laptop can easily pick out my AP (in my basement) from a distance of 100 feet, this Belkin F5D7010 PCMCIA card ($10 after MIR) can't find my AP even within 50 feet (I think both my built-in and this card using the same Broadcom chip, as well as my F5D7230 router). Reading the instruction on adding external antenna to D-Link DWL-650 and SMC-2632, I thought I could do the same to my poor card.

Opening the case is easy if you don't care much about putting it back together. I pried off the plastic cover first, the metal part was a little bit tricky, each half locked into each other through 4 slots on the plastic cover (I was only able to keep 2 of them undamaged) but who care, I'm gonna open it again and again later. While I was working on it, I use a little piece of electric tape to keep the plastic piece near the connector socket so that the card can slide into the PC slot easily.

Had a look at the inside card, I guessed the antenna, just like the DWL-650 and SMC-2632, should be connecting to some sort of capacitors. Because the other cards can operate on one modified and one unmodified antennas, I guessed the same principle could be applied here. I read about using hot-air gun to re-solder the capacitor and thought I could do the same with my soldering iron (I do have a very fine tip), but after looking at the real size of the capacitor, I changed my mind. The first idea came up to me was to use part of the antenna as a connector: disconnect it from the rest of the circuit, keep one end on the capacitor, and solder the antenna connector to the other end.

To make sure my idea is applicable, I tested a few times without doing anything to the card. I stripped off the cover of a piece of wire, stick one end to various points along one branch of the internal antennas and watch NetStumbler. Only if the contact point is closed to the capacitor, there was some signal gain. So I guess the signal dissipated through the whole rectangle area near the center of the card. I thought I should go on with the idea of separating one branch and use it as conductor only.

I only had a UHF connector available to me at that time (the one that you can find behind most TV to connect the cable). I read somewhere that it's not a right solution for connecting 2.4GHz antenna, but I'm just testing it. Cutting one branch of the antenna out of the rest of the circuit (both side of the card), I figured out that I could let it touch the connector's terminal without hard-wiring it. I scraped off the protective layer, exposing the circuit, then soldered a small drop of lead so that it will contact the terminal better. I also cut the plastic cover only deep enough so that the terminal still touch the card. I used two bolts to secure the connector to the plastic cover. After putting the card back in, I had to add several layers of electric tape on the back cover at the connector point to press the card against the connector's terminal.

That's it, put the back plastic cover in, secure it with tape (I've broken the hooks to keep them together).

This is just an attemp to test for possibility of connecting external antenna to this wireless card. Please check FCC rules before putting a modified card into use, I'm not responsible for any violation to FCC/law regulations from your action.

hoang027 at umn dot edu