Complex sentence: It's ERP at that time was 250 Watts, it was a sister station to WKZO (590 AM) in Kalamazoo which was also owned by John E. Fetzer.
Split into simpler sentences: It's ERP at that time was 250 Watts. It was a sister station to WKZO (590 AM) in Kalamazoo which was also owned by John E. Fetzer.