The UM150 EV-DO modem is compact when collapsed, but not the smallest modem on the market
Here it is with the USB connector and antenna extended. I never had to use the antenna to get a signal.
The UM150 plugged into the recessed USB port in a MacBook Air. Surprisingly it fit.
The UM150 plugged into the recessed USB port in a MacBook Air. Here you can see the handy LED lights.
A better view of the UM150 connected to the MacBook Air's recessed USB port.