One of the biggest questions we find about this spectacular phone is its 3G capabilities on the various GSM networks.
For those that purchased the N1 outright from www.Google.com/phone (Only legit way to purchase), or from a third party such as eBay, Craigslist, Amazon etc, you would expect to have it work on any GSM carrier because it's unlocked. It is true that the Nexus One is unlocked and will currently work with any GSM carrier. The 3G capabilities only work on specific carriers that match what is on the device.
Why this happens can be a mystery to some and I will explain why this is the case, and how to obtain the best matched model to work on your carrierís 3G network. Google has released two versions of the N1 so far. This allows for 3G on certain frequency bands which are carrier specific.
Currently the two sets of frequencies band are as follows:
Networks that use the 900 MHz, AWS, 1700 and 2100 MHz frequency bands such as T-Mobile US and Vodafone in Europe
Networks that use the 850 MHz, 1900 MHz, and 2100 MHz frequency bands such as AT&T in the US and Rogers Wireless in Canada
The sure way to check that you have the proper phone for your carrier is to find out the 3G frequency band they require, and then check your phone by pulling the battery and look for the PB # which is located just below the IMEI, S/N, and P/N #ís. You should see one of two PB numbers:
(A.)
1) In the phone dial pad... *#*#4636#*#* (testing menu)
2)select Phone information
3) hit the Menu key > Select radio band > [USA Band, or any other country] > OK to confirm
(B.)
Pull the battery and look for the PB # which is located just below the IMEI, S/N, and P/N #ís. You should see one of two PB numbers:
PB99110: 850 MHz, 1900 MHz, and 2100 MHz such as AT&T in the US and Rogers Wireless in Canada
PB99100: 900 MHz, AWS, 1700 and 2100 MHz such as T-Mobile US and Vodafone in Europe
I hope this helps with clarifying which N1 you have, especially if purchased anywhere other than www.google.com/phone
Additional information will become available as Verizon and Sprint versions are released.