W9WI.com/Why DTV needs virtual channels

It seems every time a few techies get together & discuss digital TV, someone decries the virtual channel system. It's confusing: most stations claim to be one channel but are actually broadcasting on a different channel. We should get rid of the virtual channel system and require every station to come up as the physical channel on which it's actually broadcasting.

NOT.

Part of the point of DTV is for the FCC to reclaim TV spectrum for land-mobile use. (cellphones) As broadcasters and DXers we may not like it, but that's what Congress has tasked the FCC with doing, and it's what the FCC will do. As spectrum is reclaimed, stations are moved around to new channels. The virtual channel system hides this moving from the viewers. It allows the viewer to know ABC will always be on channel 7; they don't need to guess where they'll find their favorite soap opera next week.

Let's look at one specific station: WBBM-TV, CBS in Chicago. And let's assume we didn't have virtual channel remapping. To watch a CBS program in Chicago:

  • Before digital: punch in "02".
  • In digital, until 2009: punch in "03".
  • In digital, after 2009: punch in "12".
  • UNLESS.. you live downtown: punch in "26".
  • OR.. you have cable/satellite: punch in "02".
  • That's four different channels to watch CBS, depending on when you're watching; what kind of TV you have; and whether you have a cable/satellite service.

    Now, let's look at the same station with virtual channel remapping. To watch a CBS program in Chicago:

  • Before digital: punch in "02".
  • In digital, until 2009: punch in "02".
  • In digital, after 2009: punch in "02".
  • UNLESS.. you live downtown: punch in "02".
  • OR.. you have cable/satellite: punch in "02".
  • It doesn't matter how you receive your TV, nor when. To watch CBS, you always punch in "02".


    Let's look at a couple of charts. The charts show which channel you'd punch in to watch each Chicago station at a specific point in the digital transition. The horizontal axis is time; the vertical is the channel number; each station has a different color line.

    This first chart assumes no channel remapping:

    Now, this second chart assumes we do remap channels:

    Is virtual channel remapping still more confusing?

    © D. Smith W9WI 2014

    Page created 2014-11-12