Balanced pair cable has higher attenuation at higher frequencies, hence the longer the wire between DSLAM and subscriber, the slower the maximum possible data rate. The following is a rough guide to the relation between wire distance and maximum data rate. Local conditions may vary, especially beyond 2 km, often necessitating a closer DSLAM to bring acceptable speeds:
25 Mbit/s at 1,000 feet (~300 m)
24 Mbit/s at 2,000 feet (~600 m)
23 Mbit/s at 3,000 feet (~900 m)
22 Mbit/s at 4,000 feet (~1.2 km)
21 Mbit/s at 5,000 feet (~1.5 km)
19 Mbit/s at 6,000 feet (~1.8 km)
16 Mbit/s at 7,000 feet (~2.1 km)
1.5 Mbit/s at 15,000 feet (4.5 km)
800 kbit/s at 17,000 feet (~5.2 km)