Before revision: 6) making it difficult to impossible to use them for digital television.
After revision: In research undertaken prior to the transition from analog to digital television broadcasting, it was discovered that electromagnetic interference from lightning, high voltage AC power transmission, AC rectifiers, and ballasts used in fluorescent lighting, greatly affected low-band VHF channels (In North America, channels 2,3,4,5,6) making it difficult to impossible to use them for digital television.