The test tubes in the last experiment bubbled over on Thursday night, when football-loving customers of some of the biggest cable companies, such as Time Warner Cable, Cablevision and Charter Communications, found themselves out of luck if they wanted to see the biggest NFC matchup of the season. NFL Network insists that it must be placed on basic service tiers, available to every customer, and not just on a sports-specific digital tier. The league wants the cable companies to pay it 70 cents per customer per month for NFL Network, which this season carries eight games, including next Thursday’s Bears-Washington game. It may not seem like much, but 70 cents is more than most cable channels charge carriers.