Improving GSM modem reception

[n1kt0]

I picked up one of these **broken link removed**because they're cheap and you can desolder the USB-serial chip inside them and get a raw serial interface that's easy to interface with a microcontroller. I've gotten this work, and I've sent and received SMS messages with success, but my problem is that signal strength is abysmal and it's basically only useable from the top floor of my home near a window. The built-in antenna is a joke -- just a chunk of metal that screws into a threaded ring.

I imagine most of the reception problems are likely due to cheap, poorly engineered electronics with poor noise rejection, but is there any sort of external antenna I could build for this thing that would eke out a little more signal strength? I'm using T-mobile USA as my service provider, by the way, so I'm interested in the GSM-1900 band specifically. I know basically nothing about RF electronics and antenna design, so feel free to treat me like a complete idiot.

 

[trash]

Actually for a self confessed idiot you seem to be doing much better than some people I know who profess to know something.
You're first port of call is of course an external antenna with some gain. Even a car mobile antenna will be much better than relying on an internal chassis antenna.

There are GSM repeaters which you can get where you can connect them to an internal and external set of antennas which will allow you move the modem internal to the building.

A good external antenna like a 1900MHz yagi, loop yagi or grid pack antenna with a good performing cable should be more than enough to do the job.
Using a bi-directional amplifier is an option, but not really the kind of thing you can build. You might be able to find a car amplifier kit which does a similar thing.

A fella I've been talking to recently has been trying a few combinations for his modem for much the same reasons. He's also had a lot of success with using an old ku band offset dish with a feed made for 1900MHz. Similar setup to this http://home-and-garden.webshots.com/photo/1209322665048941318fXFsgZ

 

[Sceadwian]

Look for chip antenna's, like those you can get from Sparkfun. More advanced external antenna like trash is talking about are incredibly good, HOWEVER, they're big, if you just want small size and best possible performance, chip antennas are the only way to go.