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Cable sega continues...heeeellppp!!

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Anonymous
November 13, 2004 3:06:08 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

Well the cable company came out Wednesday (after waiting for almost a week)
and things worked fine until today. I go to the attic to investigate
thinking maybe the amp they installed had failed. For those of you who have
followed my Cable thread you'll recall I have a RR drop and 4 T.V.'s. and
the digital channels are only on my main HDTV and these are the channels I'm
having problems with. Anyhow, as it turns out the HDTV wasn't even
receiving an amplified signal and the tech hooked up two additional outlets
that are not used.

He routed the main cable into a two way 3dB balanced splitter (rated to
1000Mhz), then one drop went directly to my RR modem and the other went into
a second unbalanced splitter with one 2dB and two 7.5dB drops. He ran my
HDTV off the single 3dB drop, one bedroom T.V. off one 7.5 drop and the
other 7.5 drop went to the input of the amplifier. The output of the
amplifier was then input into another balanced four way balanced splitter,
with 7.5 dB each.

The first thing I did was identify the two drops that were not in use and
disconnected those. I then tried connecting the main line to the input of
the amplifier and then directly into my HDTV. Regular channels were fuzzy
and no digital channels came through at all (amplifier says it's rated to
800Mhz and I understand digital cable can go up to 850Mhz, but still I think
something should have been received?). Thought maybe the signal was too
strong so I tried running the main line into the two way splitter with one
of the drops going to the HDTV, same result, and the regular channels had
hum lines scrolling. The amplifier didn't help regardless of where I put it
so I took it off line. I ran the main cable into the unbalanced three way
using the 3dB drop for the HDTV, one of the 7.5's for the RR, and then put
the third into a balance three way with three 7.5's which feeds the den and
two bedrooms. Everything works fine and looks pretty good with the
exception of the DTV channels which are still dropping out and getting
distorted. I'm back to square one. I called the cable company again and
they said they will send a lead tech this time, but it will be next
Wednesday before someone can come out.

Getting really frustrated. Do you guys thing the amplifier was defective or
the wrong type? Think I should try and buy one of my own? Maybe the cable
box (they gave me a used one off the shelf)? I'm grasping here I know, but
I don't understand for the life of me why it worked O.K. for a couple of
days, even with the screwy wiring and all the additional drops. At times it
doesn't seem like a power issue at all, but when I run straight to the main
input the problem clears. To me that clears the box, cable line, etc.??

Any idea's/help??

Thanks again
Anonymous
November 13, 2004 9:22:42 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Jack Dotson" <jdotson@stx.rr.com> wrote in message news:<Qdcld.7494$pu3.5206@fe2.texas.rr.com>...
> Well the cable company came out Wednesday (after waiting for almost a week)
> and things worked fine until today. I go to the attic to investigate
> thinking maybe the amp they installed had failed. For those of you who have
> followed my Cable thread you'll recall I have a RR drop and 4 T.V.'s. and
> the digital channels are only on my main HDTV and these are the channels I'm
> having problems with. Anyhow, as it turns out the HDTV wasn't even
> receiving an amplified signal and the tech hooked up two additional outlets
> that are not used.
>
> He routed the main cable into a two way 3dB balanced splitter (rated to
> 1000Mhz), then one drop went directly to my RR modem and the other went into
> a second unbalanced splitter with one 2dB and two 7.5dB drops. He ran my
> HDTV off the single 3dB drop, one bedroom T.V. off one 7.5 drop and the
> other 7.5 drop went to the input of the amplifier. The output of the
> amplifier was then input into another balanced four way balanced splitter,
> with 7.5 dB each.
>
> The first thing I did was identify the two drops that were not in use and
> disconnected those. I then tried connecting the main line to the input of
> the amplifier and then directly into my HDTV. Regular channels were fuzzy
> and no digital channels came through at all (amplifier says it's rated to
> 800Mhz and I understand digital cable can go up to 850Mhz, but still I think
> something should have been received?). Thought maybe the signal was too
> strong so I tried running the main line into the two way splitter with one
> of the drops going to the HDTV, same result, and the regular channels had
> hum lines scrolling. The amplifier didn't help regardless of where I put it
> so I took it off line. I ran the main cable into the unbalanced three way
> using the 3dB drop for the HDTV, one of the 7.5's for the RR, and then put
> the third into a balance three way with three 7.5's which feeds the den and
> two bedrooms. Everything works fine and looks pretty good with the
> exception of the DTV channels which are still dropping out and getting
> distorted. I'm back to square one. I called the cable company again and
> they said they will send a lead tech this time, but it will be next
> Wednesday before someone can come out.
>
> Getting really frustrated. Do you guys thing the amplifier was defective or
> the wrong type? Think I should try and buy one of my own? Maybe the cable
> box (they gave me a used one off the shelf)? I'm grasping here I know, but
> I don't understand for the life of me why it worked O.K. for a couple of
> days, even with the screwy wiring and all the additional drops. At times it
> doesn't seem like a power issue at all, but when I run straight to the main
> input the problem clears. To me that clears the box, cable line, etc.??
>
> Any idea's/help??
>
> Thanks again

Did you try just hooking the line that comes into your house directly
to the HDTV? I thought that was suggested previously. Until that
works, I wouldn't fool around with amps and splitters. If direct
doesn't work, then either the signal is already extremely poor when it
enters the house, or else something is wrong with the cable box, or
less likely, the TV. Have you tried switching out the cable box? The
tech is able to measure the signal strength on the line, which they
will do if you call them back.

As far as the amp/splitter deal, it's normal to split the cable two
ways first when it enters the house. One split goes to the cable
modem, the other feeds the TV's. IMO, the amp normally should be
placed on the TV feed after the first split so that it amplifies the
signal for all the TV's.
Anonymous
November 13, 2004 1:07:03 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Chet Hayes" <trader4@optonline.net> wrote in message
news:b81a861b.0411130622.5c0462ce@posting.google.com...
>
> Did you try just hooking the line that comes into your house directly
> to the HDTV? I thought that was suggested previously. Until that
> works, I wouldn't fool around with amps and splitters. If direct
> doesn't work, then either the signal is already extremely poor when it
> enters the house, or else something is wrong with the cable box, or
> less likely, the TV.

That's a good thing to do. If it's ok, then do an experiment
to optimize a model of the splitter system. Start by inserting
the lossy components to see how much signal margin there is
at all channels.

If you don't have any attenuators, just insert the various
splitters one-by-one and see whether cascading them degrades
any channels. Get a few male/male F connectors to allow you
to insert all these splitters at one place.

Make sure you terminate the unused splitter ports when you
do this. You can buy 75 ohm terminations at Radio Shack for
a buck or two.

By the way, the OP didn't say whether he was properly terminating
all the unused ports on the splitters. Impedance mismatches
separated by lengths of transmission line can greatly affect
performance at various frequencies. That's how bandpass and
bandstop filters are made. Even kinks in the coax or poor
connections can cause problems.

If you can't get the model topology to work, then the
problem is probably with the input signal from the cable
company.

If the model works, then start connecting the coax runs
one-by-one, and replace any bad ones.

Don
Anonymous
November 13, 2004 2:50:27 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

In article <puWdnffxQqCTvgvcRVn-2g@comcast.com> "Don K"
<dk@dont_bother_me.com> writes:

>"Chet Hayes" <trader4@optonline.net> wrote in message
>news:b81a861b.0411130622.5c0462ce@posting.google.com...

>> Did you try just hooking the line that comes into your house directly
>> to the HDTV? I thought that was suggested previously. Until that
>> works, I wouldn't fool around with amps and splitters. If direct
>> doesn't work, then either the signal is already extremely poor when it
>> enters the house, or else something is wrong with the cable box, or
>> less likely, the TV.

>That's a good thing to do. If it's ok, then do an experiment
>to optimize a model of the splitter system. Start by inserting
>the lossy components to see how much signal margin there is
>at all channels.

>If you don't have any attenuators, just insert the various
>splitters one-by-one and see whether cascading them degrades
>any channels. Get a few male/male F connectors to allow you
>to insert all these splitters at one place.

>Make sure you terminate the unused splitter ports when you
>do this. You can buy 75 ohm terminations at Radio Shack for
>a buck or two.

>By the way, the OP didn't say whether he was properly terminating
>all the unused ports on the splitters. Impedance mismatches
>separated by lengths of transmission line can greatly affect
>performance at various frequencies. That's how bandpass and
>bandstop filters are made. Even kinks in the coax or poor
>connections can cause problems.

>If you can't get the model topology to work, then the
>problem is probably with the input signal from the cable
>company.

>If the model works, then start connecting the coax runs
>one-by-one, and replace any bad ones.

All good info. I merely wanted to put in my own 2¢ worth here; do not,
under any circumstances, let yourself get talked into using "MONSTER"
brand cables or accessories. Most likely your cable company used RG-6,
perhaps even RG-6/Quad Shield, either of which is perfect and is the
recommended cable for the job.

If I could be there I think I would start at the ground block (outside)
and take a look at a full baseband spectral sweep just to get an idea of
the levels and signal tilt where it enters the home. If it's out-of-spec
at the ground block, as I rather suspect that it is, I would want to
recheck it at the mul-tee (at the pole or u/g pedestal. Quite possibly
your tap is some distance from the distribution amp. This is compensated
for by steadily decreasing tap values along the way, but doesn't
compensate for the high frequency roll-off characteristics of the
transmission line. If you can see the point where your cable line attaches
to the pole or underground pedestal, look to see if there is a number on
the underside of the tap. Something like "27" or "17", etc. The higher
this number, the closer you are to the distribution amp and the better off
you should be with your "digital" signals (those up in the 750 Mhz
region). If your tap value is a low number (anything less than 20) then it
may require a slope-correcting amplifier to rectify the situation.

Not just any amplifier will work. Digital cable as well as your cable
modem require bi-directional (two-way) devices. I would leave it all to
your cable company to provide whatever it takes to get you working. Also,
as Chet said, it is very important to terminate any unused ports on the
splitters. These terminators are little connector-looking things with a
75-ohm resistor inside.

If everything outside the house looks OK, then I would start looking at
the individual drops. Absent the fancy test gear, a quick way to eliminate
drop problems is to simply run a new line (just lay it across the floor
temporarily) and see if it gives any improvement. You could very easily
have a nail going through a concealed drop cable inside the wall.
!