Ch.7 w/Reduced Power (In DTV Transition?)

[Garrett Wollman]

<<On Thu, 29 May 2008 09:17:46 -0700 (PDT), Matthew Osborne <mattosborne1976@yahoo.com> said:

> As part of this transition they, along with all other TV stations,
> will have to reduce their OTA transmitter power output to conform to
> new and significantly lower power authorization rules.  These new
> rules are based on the finding that DTV signals are more receivable
> at lower power levels than analog

Analog TV facilities are regulated on the basis of *peak* power; the
analog signal is at its maximum when the video is blanked during a
sync pulse.  (This is because analog TV -- except in France -- uses
negative video modulation, so the maximum video amplitude represents
black.)

ATSC signals do not vary much over time, by design, so peak power is
not meaningful.  Instead, DTV facilities are regulated on *average*
power.  This accounts for most of the difference in the emission
limits.  However, the 8VSB modulation used for broadcast ATSC also
includes a couple dB of processing gain, which should further reduce
the power necessary for replication.

-GAWollman