Trying to split a cable signal ...

Trying to split a cable signal ...
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Subject Author Date
Trying to split a cable signal ... NoelSemple1 05-19-2008
Posted by Timothy Daniels on May 23, 2008, 12:22 am
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"Bill M." wrote:
> I thought the CMTS sends instructions to the modem to command it to
> increase or decrease its upstream power level on a continuous basis so
> that the upstream signal strength *at the CMTS* is within spec.

Ooops, I think you're right. The CMTS is in charge.

*TimDaniels*



NMFall 20%
Posted by Todd H. on May 22, 2008, 10:34 pm
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> "Todd H." wrote:
>>
>> That upstream power looks to be at the very edge of usability in my
>> experience.
>
>
> That generally means that the modem is transmitting at such a
> high power because it can't "hear" the downstream packets well,
> doesn't it? IOW, there's some kind of attenuation of the down-
> stream signal.

Actually it means the upstream signal is getting attenuated on its
way to the headend to and the head end during training keeps saying
"crank it up, can't hear you" until they arrive at 55dB.

> Is there a chance that the OP is using a tap, i.e. a directional
> coupler, as a splitter and he has the modem on the tapoff port of
> the coupler?

Possible. But more likely, he may be using a n inexpensive splitter
where a DC should be used. I haven't followed the whole thread, but
really this shit is best left to the cable company to do. Consumers
can't seem to easily/reasonably get their hands on the things needed
to do it right: namely, directional couplers and high quality cable
terminations, and in some cases amplifiers with a passive return are
needed (but are a last resort, as they add noise which the cable
modems hate even more than poor signal levels).

Best Regards,
--
Todd H.
http://www.toddh.net/

Posted by on May 21, 2008, 6:12 pm
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wrote:
> > We live in Toronto and have Roger's cable internet and tv. Both the
> > cable modem and the tv work perfectly when connected directly to the
> > wall. However, when I introduce a splitter and attempt to use them
> > simultaneously, the tv continues to work but the modem doesn't.
>
> > I've tried at least 5 different splitters, including a $50 monster
> > cable model, none works.
>
> > [......]
>
> > Is there any type of splitter or amplifier which would let us use the
> > net and the tv simultaneously without calling the provider and going
> > back to paying for both?
>
> A normal splitter should work. Is it possible that you used splitters
> made for satellite use? What is the passband for the splitters that you
> used? A normal splitter made for CATV and cable/internet would have
> a passband of 5MHz to 900MHz or 1,000MHz. BTW, anything made
> by Monster Cable is grossly overpriced and intended to suck money
> out of gullible people. A good splitter is cheap enough to be given away
> by the cable company. I once walked into the supply yard of the local
> cable company (now Time Warner) and asked for a splitter and offered
> to pay for it. A technician went to his truck and just gave me one and
> said to forget it.
>
> There is also the possibility that you need a filter for the TV. It keeps
> the electrical noise from the TV from getting into the cable infrastructure
> of the cable company. Some older TVs can also make enough noise to
> interfere with the upstream internet signals. These you *might* be able
> to buy at Radio Shack, but more likely you'd have to get one from your
> cable company.
>
> *TimDaniels*

Many thanks Tim for your help. I have tried 2 splitters rated
5-1000 MhZ, plus the Monster which I agree was ludicrously overpriced
even it had worked.

The problem occurs when I use the splitter with or without the tv
connected, so I think I can rule out the interference hypothesis.

Posted by Timothy Daniels on May 21, 2008, 7:44 pm
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> The problem occurs when I use the splitter with or without the tv
> connected, so I think I can rule out the interference hypothesis.

Hmmm... suspicion turns to the cable between the wall and
the splitter. Who attached the connectors for that cable and what
kind of connectors are they (e.g. hex crimp [boo], compression fit
such as SnapNSeal, Digicon, SuperLok [yayy], push-on [superBoo])?
Are the connectors sized to match the cable size? Is the cable
shielded under the outer sheath with what looks like aluminum foil
in addition to the metal braid?

*TimDaniels*



Posted by Agent_C on May 21, 2008, 2:02 pm
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On Mon, 19 May 2008 11:40:14 -0700 (PDT), NoelSemple1@gmail.com wrote:

>Is there any type of splitter or amplifier which would let us use the
>net and the tv simultaneously without calling the provider and going
>back to paying for both?

Yes, a Monster Cable TGHZ-2RF. Connect the cable modem to the "Power
Pass" lead.

A_C

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