Transmitting one watt at 900 MHz, the modems pack quite a punch, but the stock rubber-duck antennae suck. What's worse, the internal antenna connector is nonstandard, and we've been as yet unsuccessful at identifying it. Adding better antennae makes it easy to surpass the maybe-a-mile distances achievable on the stock omnis, but first, we need a way to connect those antennae.
(Note: This Instructable originally identified the stock connector as a Hirose H.FL, but we've now confirmed that this is not the case. It's very similar, but not quite identical! If better information comes down about the connector itself, it will be posted here.)
Fortunately, it's relatively easy to replace the H.FL with the much more common (and much smaller) U.FL connector, which is found on MiniPCI wireless cards, among other places. Thus modified, the modem is easy to equip with the new antenna of your choice. The operation is straightforward, and this instructable is as much about good soldering technique as it is about the specific task at hand.
Because the radio modem was certified to meet FCC Part 15 requirements with its built-in antenna, changing that antenna breaks the certification, just like changing the antenna on an 802.11 device. This may fall under part 15.23 but I'm not a lawyer and can't say for certain whether a user-modified device counts as a home-built device. Refrain from pissing people off, and the feds should have no reason to bother you.
Or, if you're an amateur radio operator, you can operate under Part 97. Either way, if half-mile links were typical on the rubber ducks, just imagine what you'll achieve with some decently directional antennae!
This is my first instructable. Please be unsparing with your constructive criticism.
Step 1: Materials, tools, and work space.
Some U.FL connectors would be nice, obviously. I got mine from Digi-Key, where they're $1.39 each as of this writing. You can also scavenge them from dead Mini-PCI wireless cards, if you have any sitting around, but removing them intact is tricky.
And of course, you'll need new antennae and cables, since the stock ones won't fit anymore. The easy availability of U.FL pigtails from a number of sources was the reason behind this instructable.
For the GT modem, you'll need a 1/16" hex (Allen) key or driver. For the GS, it's a T6 Torx.
A set of really fine needle-nose pliers is essential. I like box-joint pliers, which have less lateral play than the cheaper pin joint. Tweezers are a fine idea, too.
Get a good soldering iron, or temperature-controlled station. Get the finest tip they offer, in the neighborhood of 3/64" if it's available. I use a refurbished Edsyn 951SX "Loner" station that I got at a ham swap from EAE Sales. It's changed the way I think about solder, and is easily the best tool purchase I ever made. If you do a lot of electronics work (and you're on this site, you should!), consider it money well spent.
Paste flux is the most overlooked part of any soldering setup. Get good flux and use it every time the iron touches something. Soldering should be called "soldering and fluxing", but I guess that doesn't roll off the tongue so easily. I can't emphasize this enough, use flux! It dissolves oxides, it conducts heat, and it solves all the surface-tension problems that make soldering awkward. If you've had a bad experience with solder, I bet this is why. (If you're getting a solder station from EAE, Bruce will set you up with the right flux and solder, too.)
Oh yes, solder! For most electronics work, finer solder is better. If it's stiff enough not to droop when you extend it five or six inches, throw it back in the plumbing toolbox and get some real electronics solder. Rosin core is nice but not essential if you're using external flux.
Some desoldering braid is nice to have, too. It's cheap and it lasts a long time, so throw some on your Digi-Key order. (I do a LOT of soldering, and I can't remember the last time I reached the end of a spool of braid.)
A vise really helps. Your workbench deserves a Panavise 350 or something similar. They're made in the USA and lifetime warranted, so shell out the bucks and rest assured that your great grandkids will marvel at your foresight in buying such a useful, timeless tool.
Safety glasses. Solder and flux can spatter, and small parts can go flying. You only get one set of eyes, so please treat them well! I've been extremely pleased with the MSA SafetyWorks glasses, which I get at Home Depot. They're absurdly clear, and the lenses are very flat so they don't shift the image like other glasses I've tried. If you feel like you're underwater or on another planet when wearing safety glasses, you're wearing the wrong safety glasses. They're cheap, so keep trying new ones until you find a style you like. Then keep the old ones around for guests to use.