DIGITAL TV — Ready
or Not, Here it Comes!
February 17, 2009 — a date that may not live in infamy, but nevertheless will witness
a monumental change in the US television broadcasting landscape. On that date, all
high power analog TV transmissions will cease, marking the end of nearly 80 years of
almost continuous operation across the country. While some LPTV (low power TV)
and repeater stations may continue to operate, suffice it to say that most American
TV watchers will be affected in one way or another by this change.
by Jeff
Mazur
For the majority of us who receive
our TV signals via cable, telcos, or
DBS (direct broadcast satellite),
this event should pass with hardly a
blip on our screen. There may be a
slight interruption while broadcasters
change transmitters and set-top boxes
are reprogrammed from the head end
to receive many stations on their new
frequencies.
Cable networks (Lifetime, CNN,
etc.) — including premium channels
(e.g., HBO and Showtime), as well as
PPV (Pay-Per-View) and VOD (
Video-On-Demand) services — will not be
affected. Current plans even have
some cable companies supplying
analog signals (converted from
the new digital transmissions) so that
any TVs connected directly to the
cable (i.e., without a set-top box) will
continue to function.
It is likely, however, that prior to
the 2009 shutdown, the number of
existing analog channels on the cable
will be trimmed to a minimum. Of
course, your DVD and VCR will still
work but don’t plan on recording any
shows off air unless the recorder has
a digital tuner.
HISTORY OF US TV
The analog TV system still in
use today was designed in the
early 1930s for monochrome (black
72 October 2007
and white) broadcasting. This system
was later revised in 1953 by
the National Television System
Committee (NTSC) to accommodate
color. At that time, it was an
important goal to devise a scheme to
add color information in a way that
was compatible with the existing
monochrome signal. This was indeed
accomplished (although not before a
brief fling with a field sequential
color wheel system devised by
CBS) and it is a testament to those
engineers that the system has
remained viable all of these years
with virtually no enhancements.
When an improved High
Definition TV (HDTV) system first
began to be considered, it was
assumed that a higher bandwidth
analog signal would be required. A
few schemes were developed which
placed the extra picture resolution on
additional subcarriers. This would
have resulted in a system that could
offer compatibility with the existing
NTSC signal. Unfortunately, the extra
bandwidth this required made these
systems impractical. Digital systems
were in their infancy and compression
technology practically did not exist
at that time.
In other countries, most notably
Japan, the push towards HDTV
seemed inevitable and a few
standards began to appear. In the US,
there was a strong political pressure to
create a new system that was better
than anything else already in use. To
this end, in 1987 the FCC (Federal
Communications Commission) created the Advisory Committee on
Advanced Television Services (ACATS)
and empowered it to research all
existing technologies. With help from
the Advanced Television System
Committee (ATSC), an open call was
put out for Advanced Television (ATV)
system designs and 23 competing
analog systems were submitted.
After a long review process
however, it became apparent that a
digital system would be much more
desirable, despite the fact that this
would mean rolling out a completely
new system that would not be
compatible with the existing NTSC
standard. By 1993, there were four
digital systems being considered.
In the end, the ACATS could not
pick a single system as clearly better
than the rest. With time running out,
the four remaining participants agreed
to combine their best efforts into a
single system and thus formed the
HDTV Grand Alliance (GA). At the
last minute, the computer industry
decided to weigh in and several minor
changes were made.
By 1996, the GA system was
brought to the FCC for approval and
in April 1997 the FCC prepared to
