I bought the Sparkfun Cellular Shield SM5100B with an Arduino UNO, and Quad-band Wired Cellular Antenna SMA antenna. Hope to use it for an upcoming project. Here’s how I set it up. I followed the instructions at http://tronixstuff.wordpress.com/2011/01/19/tutorial-arduino-and-gsm-cellular-part-one/ to get the cell module working/ Everything went well till I got to the part for setting up the band for the US. I was using a T-mobile post paid SIM card. T-mobile is on the GSM850&PCS1900 i.e AT+SBAND=7. This was the message on startup
+SIND: 8 (loss of signal)
I eventually figured out that the band setting for the US was not set correctly on the module. I did that by using ZedLeps code modification at http://www.sparkfun.com/products/9607, uploading the sketch to the board, and then entering AT+SBAND=7 in the arduino serial monitor. This did the trick. I also had to hit the reset button on the UNO using a piece of plastic to reach under the shield once I made the change. This time around, success! Got +SIND: 11. eventually managed to send text messages and receive a call.