What stations still might change Feb 17 anyways.

[Scott Fybush]

Robert S Chase wrote:
> I absolutely now understand. Thanks.
> 
> Now if I could only get a list of the channels my Panasonic DVR scans on 
> Comcast cable, e.g., 44-2 on the DVR equals 209 WGBXW(orld) on the 
> Comcast box, etc. I'll be all set for Feb 17th. After we get through the 
> DTV transition maybe somebody could explain to me the whys and 
> wherefores of the channel distribution on cable
>

Cable uses a different modulation scheme than broadcast DTV. Cable's 
scheme is called QAM, and most of it is scrambled so that you can't 
receive it with your DVR.

Your cable box, as you note, uses a translation table to map those QAM 
channels for display, and the cable company can (and often does) change 
that mapping on the fly. It can also vary from headend to headend, so 
the lineup I saw last week on the Comcast system in Seekonk was rather 
different from the one I saw a day later in Newton.

Some cable systems, like my Time Warner system here in Rochester, don't 
pass along broadcasters' PSIP mapping information, so the channels I see 
with my QAM-enabled DVD recorder at home are the actual physical RF 
channels the cable company is using - i.e., when WUHF's standard-def 
signal appears as "82.1" on my box, it's really traveling down the cable 
on RF channel 82.

Other systems, like Comcast, do pass at least some of the PSIP, so many 
of the broadcast stations remap on QAM tuners - i.e. "44.2" for WGBH 
World. It might be traveling on RF channel 78 or 79, but you'd never 
know that in this case.

(A cable company can't use the same RF channel for analog and for QAM, 
and it can pack many more program streams into a QAM channel than into 
an analog channel, which is why cable companies are itching to eliminate 
analog service completely.)

Generally, the only unscrambled QAM channels you'll see are the local 
channels (SD, HD and whatever subchannels the broadcasters offer through 
cable), plus local access and maybe one or two others - NECN, for 
instance, showed up on the Comcast systems I was watching last week, and 
for some reason I get Lifetime Real Women on Time Warner here.

As you'd imagine, the cable companies would rather rent you a box for $8 
a month than have you tune in QAM channels for free - and they're thus 
loath to publicize the channel lineups. But a Google search of your 
community name, your cable company and "QAM lineup" will usually yield 
the relevant thread on AVSForum, where the helpful members tend to keep 
good track of what's available where.

Hope that makes sense...if there's interest, I'd be happy to post the 
lineups I saw on the two Comcast systems I was hooked up to last week.

s