IRVING, TEXAS and BALTIMORE —Nexstar and Sinclair, which together run 343 television stations reaching 60 percent of the country, are joining forces to launch ATSC 3.0, the so-called “Next-Gen” broadcast transmission standard now in its later stages of completion. The two broadcast groups said they have entered into a memo of understanding to establish “a consortium that will promote spectrum aggregation, innovation and monetization and enhance their abilities to compete in the wireless data transmission sector.”