Complex sentence: WNET struggled against dominant WJAR because television manufacturers were not required to include UHF tuning capability, and viewers had to buy an expensive converter in order to receive WNET; even then the picture quality was marginal at best.
Split into simpler sentences: WNET struggled against dominant WJAR because television manufacturers did not have to include UHF tuning capability. To watch WNET, viewers had to buy an expensive converter but even then picture quality was marginal at best.