Re: Modulation and Digital Cable with Comcast

[tomvaldes@xxxxxxxxxxx]

I checked the diagnostics on my DCT2000 and also checked the digital
channels that I watch.  It seems that of those channels, the highest
frequency used by my digital channels is 741mHz (mostly HBO channels).
If I use the LPF-750 would that leave the channels at the 741mHz
intact? or is 741 too close to 750 that it would eat those channels?

RM wrote:
> That's because digital channels are compressed and occupy a range of
> frequencies just above your analog frequencies.  Analog CATV channels
occupy
> frequencies starting around 55.25Mhz with a bandwidth of 6Mhz per
channel.
> Digital channels, on the other hand, roughly occupy 1Mhz per channel,
> depending on the carrier.  I think most CATV providers put their
digital
> channels somewhere starting above the 450 or 500 Mhz range.  In our
case
> (time warner), it's above channel 74 which is 523Mhz.  (Don't let
Channel 95
> to 99 fool you.  They are actually located around channel 7 in the
freq
> domain).  Channel 116 would be roughly 750Mhz.  If you are losing
digital
> channels when injecting at 77 which is ~540Mhz, its probably safe to
assume
> that Comcast is similar to Time Warner, and starts around 530Mhz.  If
so,
> 750 to 530 is 220Mhz or 220 Digital channels give or take a few.
Given that
> most systems have 500 or more digital channels, I would guess that
the LPF
> would kill many of your digital channels.
>
> Not what you wanted to hear, but this has been a common problem for
those
> with digital cable and modulators.  I've always recommended running
two
> RG6's to each TV to solve this.  One RG6 would contain your analog
channels,
> LPF and modulated channels.  The second RG6 would carry your
unaltered CATV
> feed straight to your Digital STB and use component/s-video/composite
out of
> the STB to your TV.  Then you just use your TV remote to select
between
> tuner or video 1 (eg).
>
> Another alternative is to move your Digital STB to the modulator and
> modulate it, but then you are turning your nice digital channels into
a
> composite grade video signal.
>
> <tom> wrote in message news:6tCdneY_dMmdYKzfRVn-rQ@xxxxxxxxxxxxxxx
> > I have Comcast Digital Cable for my home. The box is a Motorola
DCT-2000.
> > I also have a Channel Plus 5445 (4-channel modulator)
> >
> > I am able to inject 4 channels into my home signal but I have a few
> > questions / problems.
> >
> > Depending on what channel I inject to ( 77, 79, 81, 83), I lose
some
> > of my digital channels.  The channel displays something similar to
,
> > "signal unavailable should be available soon".  If I disconnect my
> > modulator the channels appear fine.  If I choose different channels
to
> > inject to, I lose different digital channels.
> >
> > How can I find which channels are available for creating modulated
> channels?
> > Also, I'm unclear on Low Pass Filters
> > The ChannelPlus Low Pass Filter  LPF-750 passes CATV channels 2 to
116
> > Would this work?  Does Comcast use any channels higher than 116?
> >
> > thanks,
> > tom
> >
> >