Suggest a USB GSM modem?

I’m looking for a USB GSM modem to use with my BeagleBone Black / linux. An external antenna connector is a must. Any suggestions for devices which work well with these boards?


first question - where are you? what gsm bands do you need to cover?

I have used the Nokia CS 12 successfully. Cheap at around $30 used.
My blog gives some info about using it: