Terri Pannett writes:
>What do these boxes do besides convert the signal?  What do we need to be 
>able to use them?

	They are meant for over-the-air reception. If you live
in a city, a pair of rabbit ears might work and then again, they
might work sporadically. Most of the signals you will be
receiving will be UHF channels but a few digital channels had to
be stuck on VHF channels because there wasn't enough room.

	What I have been told by someone who has a VCR with a
digital tuner is that when you first connect the antenna, you
need to give it the program command at which point, it scans all
the broadcast TV channels. There is apparently a continuous ID
signal embedded in the data which tells your digital converter
which channels in the digital world belong with which analog
channels. If, for instance, you have Channel 4 over the air,
your digital tuner will scan and hopefully pick up a digital
channel serving Channel 4.1. If Channel 4 sends multiple digital
feeds, then you will have 4.1, 4.2 and so forth. If the station
is not sending high definition video, you might have Channels
4.1 through 4.6. 4.1 is usually the same feed as just 4 but 4.2
through whatever can be several independent program sources.

	In Oklahoma and other states in what is called Tornado
Alley, many stations run a continuous weather feed with radar on
one of their digital channels.

	We have a religious broadcaster in Oklahoma City who
sends 5 feeds, one of which is a Spanish Language version of the
channel.

	Our Educational channel has a couple of feeds and used
to have 3 or 4 feeds but dropped a couple of them due to signal
quality considerations. There are just so many bits to go around
and the more feeds, the more compression they have to use so the
signal becomes bad to see and hear.

	I think the plan is to remove the few digital channels
that are on HF after the analog UHF stations go away so the end
result at least one day, will be that TV in the United states is
all UHF.

	I realize that this is a long message and is not
amateur-radio related, but it is communications technology on
the cutting edge.

	Each TV channel has 19 megabits per second to play
around with and there may come a time when hams will be allowed
to generate those same signals on the amateur bands.  I don't
know how much overhead for error correction and the like there
is, but that is a pretty healthy pipe which could make for some
really neat repeater backbones instead of the traditional analog
links. Something to think about, anyway.

Martin McCormick WB5AGZ  Stillwater, OK 
Systems Engineer
OSU Information Technology Department Network Operations Group