Complex sentence: The extended mediumwave broadcast band, commonly known as the (AM) expanded band, is a broadcast frequency allocation which moved the upper limit of the AM bandplan from 1610 to 1700 kHz.
Split into simpler sentences: The extended mediumwave broadcast band, commonly known as the (AM) expanded band, is a broadcast frequency allocation. It moved the upper limit of the AM bandplan from 1610 to 1700 kHz.