Band 66 includes band 4 . It is an expansion and superset of that band. Band 4 included AWS blocks A-F, as part of the AWS-1 auction. Band 66 adds blocks G-J (AWS-3) and the unique AWS-4 block.
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T-Mobile’s 4G LTE network uses bands 4/66 (AWS), 12, 2 (PCS), and 71 (600 mHz) . The 4G network acquired from Sprint uses bands 25, 26, and 41. For 5G, T-Mobile is using band 71 (600 MHz) for low-band, band 41 (2,500 Mhz) for mid-band, as well as faster mmWave in select downtown areas.
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