Re: Modulation and Digital Cable with Comcast

["RM" <trash@xxxxxxxxx>]

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
>
>