Certain cable stations weak -- why?

D

DaveC

Guest
I've just moved in to a new apartment. The Comcast cable service I've just
gotten is a bit above basic. It's got local stations, Travel, Food,
Discovery, Golf, Sci-Fi, History, and a few others.

All are clear except ch 36 - Sci-Fi (sound is 8/10; picture 6/10); and ch 37
- TNT (sound 0/10; picture 3/10).

How can this be? Isn't cable, by definition, a medium whereby all sources are
either good or bad? How can certain segments of the spectrum be effected and
not others? Can connections and/or patch cables I'm using in my home
entertainment system effect only these two frequencies? My neighbors in the
complex have a clear signal on these two channels.

I've scheduled a repair for next week, but I'd like to understand the "why"
behind the problem.

Thanks,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
 
Hi Dave,

Signals may depend on several components in the circuit.

Because I dont know where you live there could be several causes.

The signal delivered by cable can be to strong or to weak.
The cable or wallbox in the house installation or between the wallbox and
the ktv/vcr is bad shielded or bad quality
The coaxial cable i'sn't good installed, small shield-wire towards the inner
conductor or bad shielded so outside signals are coming into the cable,
mixing with signals in the coaxial cable.
A cryptbox for paytv or a vcr is not good alligned, (the modulator for the
rf-signal)
A t-splitter for a second tv is inferior.
The tv-set also can be sensitiver than another one.

So a lot of problems can cause it. I know it and have seen it many times and
find it out by measuring and experience in 21 years.

Greetings Peter

"DaveC" <me@privacy.net> schreef in bericht
news:0001HW.BC832F4B0003B06CF04885B0@news.individual.net...
I've just moved in to a new apartment. The Comcast cable service I've just
gotten is a bit above basic. It's got local stations, Travel, Food,
Discovery, Golf, Sci-Fi, History, and a few others.

All are clear except ch 36 - Sci-Fi (sound is 8/10; picture 6/10); and ch
37
- TNT (sound 0/10; picture 3/10).

How can this be? Isn't cable, by definition, a medium whereby all sources
are
either good or bad? How can certain segments of the spectrum be effected
and
not others? Can connections and/or patch cables I'm using in my home
entertainment system effect only these two frequencies? My neighbors in
the
complex have a clear signal on these two channels.

I've scheduled a repair for next week, but I'd like to understand the
"why"
behind the problem.

Thanks,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
Click to expand...
 
On Sun, 21 Mar 2004 12:49:55 -0800, eddumweer wrote
(in article <c3kv5m$830$1@news3.tilbu1.nb.home.nl>):

Hi Dave,

Signals may depend on several components in the circuit.

Because I dont know where you live there could be several causes.

The signal delivered by cable can be to strong or to weak.
The cable or wallbox in the house installation or between the wallbox and
the ktv/vcr is bad shielded or bad quality
The coaxial cable i'sn't good installed, small shield-wire towards the inner
conductor or bad shielded so outside signals are coming into the cable,
mixing with signals in the coaxial cable.
A cryptbox for paytv or a vcr is not good alligned, (the modulator for the
rf-signal)
A t-splitter for a second tv is inferior.
The tv-set also can be sensitiver than another one.

So a lot of problems can cause it. I know it and have seen it many times and
find it out by measuring and experience in 21 years.
Click to expand...
-=-=-=-

But all of these problems should effect all the channels *equally*, yes?

I don't have any "cable box"; this is basic cable, with no HBO or other
premium service (those require a cable box, yes?)

The cable comes in the apartment right to the TV. (No VCR.)

I just can't imagine anything in the circuit that would effect only certain
parts of the spectrum, and to such a degree!

Thanks,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
 
On Sun, 21 Mar 2004 11:38:51 -0800, DaveC <me@privacy.net> wrote:

I've just moved in to a new apartment. The Comcast cable service I've just
gotten is a bit above basic. It's got local stations, Travel, Food,
Discovery, Golf, Sci-Fi, History, and a few others.

All are clear except ch 36 - Sci-Fi (sound is 8/10; picture 6/10); and ch 37
- TNT (sound 0/10; picture 3/10).

How can this be? Isn't cable, by definition, a medium whereby all sources are
either good or bad? How can certain segments of the spectrum be effected and
not others? Can connections and/or patch cables I'm using in my home
entertainment system effect only these two frequencies? My neighbors in the
complex have a clear signal on these two channels.

I've scheduled a repair for next week, but I'd like to understand the "why"
behind the problem.

Thanks,
Click to expand...
I suspect there is a filter in your feed intended to cut out channels
37 (or perhaps 36) and up.

On my cable service, I'm paying for up to channel 43 (and there are
some higher free channels). 43 comes in fine, but 44 has barely
usable video, and just detectable sound.

If you believe you should be getting channels above 36, complain to
the cable company - perhaps the previous tenant had a more limited
service, and they should change the filter to suit your subscription.

--
Peter Bennett, VE7CEI
peterbb (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
 
DaveC wrote:

But all of these problems should effect all the channels *equally*, yes?

I don't have any "cable box"; this is basic cable, with no HBO or other
premium service (those require a cable box, yes?)

The cable comes in the apartment right to the TV. (No VCR.)

I just can't imagine anything in the circuit that would effect only certain
parts of the spectrum, and to such a degree!

Thanks,
Click to expand...
Its not all that uncommon. Most any incongruity in the 'works' will
have varying effects across the entire bandwidth....in fact, affecting
all channels equally would be somewhat rare if you actually looked at
the signal level channel by channel.
If you swept it with a sweep generator you'd see a notch. The actual
freq of the notch, in your case around 300 MHz, is usually somehow
related to the wavelength of the cable from the 'bad' thing to the next
closest thing like a connector which is less than a perfect match. You
get a reflection and at the wavelength where it falls 180 degrees out of
phase is where you get the notch due to cancellation of the signal
caused by the reflection.
Thats basically what causes it but as you can imagine all that theory
isn't much use for troubleshooting. Just look for the 'bad' thing.

-Bill M
 
Peter Bennett wrote:

I suspect there is a filter in your feed intended to cut out channels
37 (or perhaps 36) and up.

On my cable service, I'm paying for up to channel 43 (and there are
some higher free channels). 43 comes in fine, but 44 has barely
usable video, and just detectable sound.

If you believe you should be getting channels above 36, complain to
the cable company - perhaps the previous tenant had a more limited
service, and they should change the filter to suit your subscription.

Duh, after my 'scientific' reply in another post I think Peter might
Click to expand...
have hit it the nail on the head. 36/37 is a very common cutoff point
for filters.

-Bill M
 
On Sun, 21 Mar 2004 17:24:57 -0800, Peter Bennett wrote
(in article <lpfs5097golrkklhacp64qvfg3mot8nuel@news.supernews.com>):

I suspect there is a filter in your feed intended to cut out channels
37 (or perhaps 36) and up.

On my cable service, I'm paying for up to channel 43 (and there are
some higher free channels). 43 comes in fine, but 44 has barely
usable video, and just detectable sound.

If you believe you should be getting channels above 36, complain to
the cable company - perhaps the previous tenant had a more limited
service, and they should change the filter to suit your subscription.
Click to expand...
Hmm... sounds like my situation. I get up to and including 36 (where quality
goes to hell). I get 69 and above, but nothing between 37 and 68. The
behavior seems very much like a notch filter.

Why filter these channels? Aren't they encoded? Don't they require a "Cable
Box" for those premium channels? I thought they did away notch filters long
ago. Isn't encryption and sync technologies what are employed to keep people
from seeing unpaid-for programming?
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
 
DaveC wrote:
On Sun, 21 Mar 2004 12:49:55 -0800, eddumweer wrote
(in article <c3kv5m$830$1@news3.tilbu1.nb.home.nl>):


Hi Dave,

Signals may depend on several components in the circuit.

Because I dont know where you live there could be several causes.

The signal delivered by cable can be to strong or to weak.
The cable or wallbox in the house installation or between the wallbox and
the ktv/vcr is bad shielded or bad quality
The coaxial cable i'sn't good installed, small shield-wire towards the inner
conductor or bad shielded so outside signals are coming into the cable,
mixing with signals in the coaxial cable.
A cryptbox for paytv or a vcr is not good alligned, (the modulator for the
rf-signal)
A t-splitter for a second tv is inferior.
The tv-set also can be sensitiver than another one.

So a lot of problems can cause it. I know it and have seen it many times and
find it out by measuring and experience in 21 years.


-=-=-=-

But all of these problems should effect all the channels *equally*, yes?

I don't have any "cable box"; this is basic cable, with no HBO or other
premium service (those require a cable box, yes?)

The cable comes in the apartment right to the TV. (No VCR.)

I just can't imagine anything in the circuit that would effect only certain
parts of the spectrum, and to such a degree!

Thanks,
Click to expand...
Remember to take into account also that the cable
system can't deliver more than they have...

In other words, perhaps their front end is getting
a lousy feed to begin with.

It might be interesting to see what/where those
stations are in relationship to you. Are they
perhaps 75 miles away being picked up off air?

Just a thought...

Ken
 
On Sun, 21 Mar 2004 19:15:34 -0800, DaveC <me@privacy.net> wrote:

On Sun, 21 Mar 2004 17:24:57 -0800, Peter Bennett wrote
(in article <lpfs5097golrkklhacp64qvfg3mot8nuel@news.supernews.com>):

I suspect there is a filter in your feed intended to cut out channels
37 (or perhaps 36) and up.

On my cable service, I'm paying for up to channel 43 (and there are
some higher free channels). 43 comes in fine, but 44 has barely
usable video, and just detectable sound.

If you believe you should be getting channels above 36, complain to
the cable company - perhaps the previous tenant had a more limited
service, and they should change the filter to suit your subscription.

Hmm... sounds like my situation. I get up to and including 36 (where quality
goes to hell). I get 69 and above, but nothing between 37 and 68. The
behavior seems very much like a notch filter.

Why filter these channels? Aren't they encoded? Don't they require a "Cable
Box" for those premium channels? I thought they did away notch filters long
ago. Isn't encryption and sync technologies what are employed to keep people
from seeing unpaid-for programming?
Click to expand...
Depends on your local cable provider. Some have terrible service, the
shoddiest quality.
It all comes down to costs. That's why many areas are still running on
old tech.
Our local service(Cox) still offers analog cable service and still
employs those inline notch filters to cut out the lower tier premium
channels.
In our area I believe it was channel 47 and a couple of others around
the lows 50's.(Cinemax, Showtime etc..)
I threw inthe towel with cable providers some time back and went with
dish which has given us much better service, picture and price.
 
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