T-Mobile versus AT&T Mobility 3G questions [telecom]

T-Mobile's 3G in the USA uses 1700 MHz; AT&T's 3G in the USA, and pretty much every other 3G carrier elsewhere in the known GSM universe, uses 1900 MHz. So your at&t 3G-capable phone (using 1900 MHz) will see 3G speeds pretty much everywhere (using any SIM that is recognized locally as an active roaming partner's), while your T-Mobile 3G-capable phone (using 1700 MHz) will see 3G speeds only in the USA on the US T-Mobile 1700 MHz 3G network (using any SIM that is recognized by T-Mobile USA as an active roaming partner's).

In short: it's the radio in the phone, not the issuer of the SIM, that determines whether that phone will be able to exploit the local 3G service. At&t uses the same 1900 most of the rest of the world uses; T-Mo USA uses 1700 instead.

HTH. Cheers, -- tlvp

T-Mobile's AWS 3G uses 1700/2100 Mhz combination for 3G. AT&T uses

You don't mention which phone or device you're attempting to put on a network. If it's a device like the iPhone if you use it on T-Mobile you'll only get EDGE since its internal radio only can use 3G at 850 and 1900 Mhz combined with 2100 Mhz. It all depends on what device you're using and if the device is capable to use T-Mobile's AWS bands with combination of 1700/2100. It will revert to EDGE or if no EDGE to GPRS.

It should work fine in any area that uses GSM for voice using 850,