You don't need the entire 6 mhz. in terms of getting a usable lower definition (e.g. 480 or 720 instead of 1080) picture--but the way the system works you still use the entire 6 mhz. TV channel to transmit the digital information.
So the Commission's concept of two stations sharing the one channel (and transmitter) is viable (just as, for example, our local U carries NBC on one portion of the stream and Fox on the second portion of the stream). But it is not possible, for example, for a tv station to use the first 3 mhz. of the channel and then auction off the second 3 mhz. for use by a digital service provider with their own, separate, antenna and transmitter.
So the Commission's concept of two stations sharing the one channel (and transmitter) is viable (just as, for example, our local U carries NBC on one portion of the stream and Fox on the second portion of the stream). But it is not possible, for example, for a tv station to use the first 3 mhz. of the channel and then auction off the second 3 mhz. for use by a digital service provider with their own, separate, antenna and transmitter.