Sean Captain’s extensive guide last week to next year's nationwide digital TV conversion featured some interesting comments from the vice president of Centris, a company that recently published a study suggesting the upcoming switchover to digital-only television broadcasts may leave millions of people across the country without a TV signal. The National Telecommunications and Information Administration is offering people who have an analog TV a $40 coupon to put toward a converter box. Unfortunately, Centris VP Barry E. Goodstadt says, in certain pockets of the country, using a converter box still won’t give you a signal if you don’t have a powerful-enough antenna.