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ATT and T-Mobile 3G Network's in the United States

3G AT&T & T-Mobile

AT&T 3G Phones:
If you want to use 3G speeds on AT&T's 3G network keep the following in mind. AT&T Uses 850 mhz & 1900 Mhz for its 3G network. An example would be the Iphone 3G it has 3G HSDPA 850 / 1900 / 2100 Mhz Frequency Bands Built into it. The HSDPA 850/1900 Mhz allow it to run on AT&T's 3G network.
The Iphone 3G also has 2G GSM 850 / 900 / 1800 / 1900 mhz frequency bands please don't confuse these 2G bands with 3G. a lot of phones are 2G GSM with these four bands but this doesn't mean they can run on a 3G network.

ATT Apple Iphone 3G

T-Mobile 3G Phones:
If you want to use 3G speeds on T-Mobile 3G network keep the following in mind. T-Mobile Uses 1700 mhz & 2100 Mhz for its 3G network. An example would be the T-Mobile G1 Phone it has 3G HSDPA 1700 / 2100 Mhz Frequency Bands Built into it. The HSDPA 1700/2100 Mhz allow it to run on T-Mobile 3G network.

The T-Mobile G1 also has 2G GSM 850 / 900 / 1800 / 1900 mhz frequency bands please don't confuse these 2G bands with 3G. a lot of phones are 2G GSM with these four bands but this doesn't mean they can run on a 3G network.

T-Mobile HTC G1

you can use the following method to determine if a phone will work on a carriers 3G network. First find out what frequencies a carrier is running it's 3G network on. 2nd check the phones umts/hsdpa frequencies.

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