Digital Television Secondary Channels
Secondary channels are channels that broadcast stations have in addition to their primary feed. Here are two real world examples:
My local CBS affiliate operates on 42.1. They also have a secondary channel that they distribute on 42.2, which is now the Retro Television Network. My local ABC affiliate also utilizes a secondary channel, which they have 24-hours of weather.
Secondary channels are made possible by digital technology. This is one advantage of digital television over analog - the ability to transmit multiple streams of video content.
It is my belief that one day we'll see a major network (CBS, ABC, FOX, NBC) try to compete against cable and satellite by striking deals with cable-only channels and bring cable television to the free airwaves.
In theory, my thought works like this: ABC brings their family of stations, like ABC Family and ESPN to free television. Now, this theory has obstacles. Mostly, the loss of revenue generated from cable and satellite transmission.
So, my latest thought is that a broadcast network will make deals with syndicated channels, like the Retro Television Network, but offer more current programming. Or, begin broadcasting on a secondary channel an all-news station with hopes of attracting more viewers throughout the day.
Whatever scenario the future holds for secondary channels, the antenna user stands to gain rather than lose programming once the digital transition becomes effective and broadcast stations figure out what to do with their secondary channels.

