| Author |
Message |
Holophote
Guest
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 Posted:
Mon Sep 19, 2005 3:55 am Post subject:
Need Notch Filter Info |
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Comcast is the only major provider of
cable service in the town where I live.
I've seen cable service guys come into
my yard (as well as my neighbors) and
consistently do a poor job replacing
a splitter box, stringing a new cable,
etc. Usually, if they manage to replace
all the cables after hanging a six port
splitter they rarely tighten the connectors.
I've actually seen cables drop to the
ground!
Many years ago I earned a little extra
money by setting up small CATV and MATV
systems. When it was time to replace the
old, brittle cable coming from the pole to
my house I decided to do it myself. I did
such a neat and tidy job I almost felt like
I should rub some sandpaper over the cable
jacket so it would match the other five
cables coming from the splitter box!
Anyway, I noticed something that needs
explaining. A couple of the ports had
notch filters hanging off of them. (At
least they looked like notch filters.)
Unless things have changed, a notch filter
will only unscramble one premium channel.
If you want to unscramble three channels you
need three filters and a switch box that
allows you to switch each filter in or out
of the cable line. Is Comcast using a single
notch filter to provide it's higher paying
customers access to all the premium channels
that would be scrambled with a basic cable
subscription? The system that's used in my
area scrambles the picture but not the sound.
My cable runs through the attic wall to a high
quality amplifier/splitter combination. From
there the cables are routed through the walls
to the various rooms in the house. If I was so
inclined, could I purchase a notch filter similar
to the one Comcast is using and install it at
the front end of the amplifier? Perhaps it would
also be a good idea to use a passive DC blocker
trap to prevent detection.
If anyone is familiar with the type of notch
filter Comcast is hanging off their splitter
boxes, and where I can purchase one just like
it I would appreciate the info. (A kit is
definitely ok too!)
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Ed Nielsen
Guest
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| Posted:
Mon Sep 19, 2005 4:42 am Post subject:
Re: Need Notch Filter Info |
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Holophote wrote:
| Quote: | Comcast is the only major provider of
cable service in the town where I live.
I've seen cable service guys come into
my yard (as well as my neighbors) and
consistently do a poor job replacing
a splitter box, stringing a new cable,
etc. Usually, if they manage to replace
all the cables after hanging a six port
splitter they rarely tighten the connectors.
I've actually seen cables drop to the
ground!
Many years ago I earned a little extra
money by setting up small CATV and MATV
systems. When it was time to replace the
old, brittle cable coming from the pole to
my house I decided to do it myself. I did
such a neat and tidy job I almost felt like
I should rub some sandpaper over the cable
jacket so it would match the other five
cables coming from the splitter box!
Anyway, I noticed something that needs
explaining. A couple of the ports had
notch filters hanging off of them. (At
least they looked like notch filters.)
Unless things have changed, a notch filter
will only unscramble one premium channel.
If you want to unscramble three channels you
need three filters and a switch box that
allows you to switch each filter in or out
of the cable line. Is Comcast using a single
notch filter to provide it's higher paying
customers access to all the premium channels
that would be scrambled with a basic cable
subscription? The system that's used in my
area scrambles the picture but not the sound.
My cable runs through the attic wall to a high
quality amplifier/splitter combination. From
there the cables are routed through the walls
to the various rooms in the house. If I was so
inclined, could I purchase a notch filter similar
to the one Comcast is using and install it at
the front end of the amplifier? Perhaps it would
also be a good idea to use a passive DC blocker
trap to prevent detection.
If anyone is familiar with the type of notch
filter Comcast is hanging off their splitter
boxes, and where I can purchase one just like
it I would appreciate the info. (A kit is
definitely ok too!)
|
Probably what you are seeing are High-Pass filters placed on the drops
of subs who do NOT have Internet via Comcast. Keeps down noise in the
return path.
CIAO!
Ed N. |
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Gary Tait
Guest
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| Posted:
Mon Sep 19, 2005 4:42 am Post subject:
Re: Need Notch Filter Info |
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"Holophote" <h_markston@hotmail.com> wrote in
news:1127084123.621488.67960@g43g2000cwa.googlegroups.com:
| Quote: | Anyway, I noticed something that needs
explaining. A couple of the ports had
notch filters hanging off of them. (At
least they looked like notch filters.)
Unless things have changed, a notch filter
will only unscramble one premium channel.
If you want to unscramble three channels you
need three filters and a switch box that
allows you to switch each filter in or out
of the cable line. Is Comcast using a single
notch filter to provide it's higher paying
customers access to all the premium channels
that would be scrambled with a basic cable
subscription? The system that's used in my
area scrambles the picture but not the sound.
|
No, likely they are filter in out bands of channels, as one point of
access before a box is issued.
| Quote: | My cable runs through the attic wall to a high
quality amplifier/splitter combination. From
there the cables are routed through the walls
to the various rooms in the house. If I was so
inclined, could I purchase a notch filter similar
to the one Comcast is using and install it at
the front end of the amplifier? Perhaps it would
also be a good idea to use a passive DC blocker
trap to prevent detection.
|
For what purpose?
| Quote: | If anyone is familiar with the type of notch
filter Comcast is hanging off their splitter
boxes, and where I can purchase one just like
it I would appreciate the info. (A kit is
definitely ok too!)
|
If you need one, especially if it is used to control access to pay
programming, you have to arrange to get one through the provideder,
Comcast. |
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Lorenzo
Guest
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| Posted:
Mon Sep 19, 2005 4:42 am Post subject:
Re: Need Notch Filter Info |
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I don't know your Comcast configuration, but what you're talking about
are called positive traps. Each positive trap unscrambles one channel.
This is old technology. My Comcast system stopped using them maybe 10
years ago. My recently rebuilt Comcast system (70 analog channels,
fiber to the neighborhood, digital channels, and cable modem) now only
uses bandstop notch filters for customers that take broadcast basic
service (roughly 30 analog channels with optional cable modem service)
These filters allow sub band (cable modem upstream), channels 2-30-
(basic service), and a few channels in the 70's where the modem
downstream signals are. All other channels are blocked or digital
only. There is another filter that might be used but it's use is
frowned upon. This filter blocks the sub band and might be used where
there's poorly shielded wiring in a customer's house that is allowing
radio transmitters and other interferance into the sub band area which
might impare modem use. The proper fix for this is to find the bad
cable or connectors and replace/repair them.
--
Lorenzo, Posted this message at http://www.SatelliteGuys.US |
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Holophote
Guest
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| Posted:
Mon Sep 19, 2005 8:11 pm Post subject:
Re: Need Notch Filter Info |
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OK guys.
My brain is still back in the stone age. My interest
in all things electronic (especially radio and TV)
started when I was nine or ten years old. I guess
I forgot how complex modern cable systems really
are.
I think Ed Nielson has got it right. No one would
hang an old fashioned notch filter off a main splitter
box feeding several homes. A high-pass filter is
probably what I'm seeing.
Thanks Gary, Lorenzo, and Ed. |
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Holophote
Guest
|
| Posted:
Mon Sep 19, 2005 8:24 pm Post subject:
Re: Need Notch Filter Info |
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OK guys.
My brain is still back in the stone age.
My interest in all things electronic
(especially radio and TV) started when
I was nine or ten years old. I guess
I forgot how complex modern cable systems
really are.
I think Ed Nielson has got it right. No
one would hang an old fashioned notch filter
off a main splitter box feeding several homes.
A high-pass filter is probably what I'm seeing.
Thanks Gary, Lorenzo, and Ed. |
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