🚀 go-pugleaf

> >I hope the "clean break" approach wins out too.  What a engineer's nightmare
> >it would be to match up the side panels to the NTSC center.

> I heard that the FCC said they wouldn't approve the standard unless its
> backwards compatible...=-(


The FCC has said broadcasters may have no more than an additional 6 MHz (not
necessarily contiguous with their existing frequency allocation.  They
can use the allocation either to:

1.  transmit the "additional" resolution and picture size to be added to
the NTSC signal on their existing 6 MHz allocation.

2.  transmit an _entire_ HDTV picture.  Old sets will be serviced by
continuing to broadcast the same programming using an NTSC signal on the
original spectrum allocation.

While at first glance it would seem easier to send HDTV using the full
12 MHz from both allocations (alternative 1), the problems of combining
the two signals-- and living with the defects of existing NTSC-- are
such that most technical proposals are along the lines of option 2.  

Option 2 has the additional virtue that after a few decades when no one
has NTSC sets any more, the stations can stop broadcasting in NTSC
altogether, and reuse the spectrum for some other purpose (more HDTV
programs, land mobile radio, etc.)