Wavy Lines off one side of splitter - AVS Forum
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post #1 of 7 Old 05-13-2010, 10:46 AM - Thread Starter
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I apologize, as this is a cross-post, but this forum seemed more appropriate for it and I couldn't figure out how to delete it from the other forum...

Hello -

I recently had Time Warner Cable installed at my house - both TV/DVR and Internet. Our house is 650' off the road, and when it was being built the builder coordinated with Time Warner and they pulled the big cable (1-1.5" in diameter) to what I believe is an amplifier about 75-100' from the house. From there it switches to an orange cable that comes into the house.

In the house, the Cable technicians set me up like follows:


The internet is fine - I'm peaking at about 26Mb download and about 1.5Mb upload

The DVR (a Scientific Atlanta Explorer 8300HDC)/TV combo works fine.


They set me up with one extra jack that the technician said could be simply plugged into anything that could decode analog cable signals for the first 70 channels. I ran QuadShield Coax (RG-6 from Monoprice) to that jack and plugged on my EyeTV 250 and I get the following picture:


So I am looking for help as to why the secondary picture is coming out so wavy. Do I need to order a better splitter? The rest of the system works fine, so the splitter is the only thing I can think of.

[EDIT] I took my machine with the EyeTV 250 attached to it downstairs where the splitter is, and attached a short 6' RG-6 cable that the installers left for me between the EyeTV 250 and the splitter. It made no difference in the signal, so I believe the cable run from the splitter to my office is fine. I believe the issue is at the splitter. Also, when looking at the "Signal Strength" reading in the EyeTV software, it gives me a strength reading of 29%. Not sure if that's accurate or even helpful, but there you are.
[/EDIT]

Thanks!
Jim
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post #2 of 7 Old 05-13-2010, 11:45 AM
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Perhaps that's AC Ripple due to the DC device power supply. I suspect the MAC itself if it's powered by a wall wart. Is the wall wart AC plug polarized? If not, reverse the plug. As a non-tech, that's where I would start. Your results may vary.

Addendum: Years ago our local cable service had those same wavy (herringbone) lines on their channel 19. Channel 19 was reserved for a service that few watched--Tempo--but I watched some pretty obscure movies on Tempo. When NBC bought out Tempo, rebranding it as CNBC, their new network got a better channel location without the wavy lines.

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post #3 of 7 Old 05-13-2010, 12:38 PM
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I'd give TW a call to diagnose.
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post #4 of 7 Old 05-15-2010, 07:39 AM
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What channel is that? Are you seeing the same noise on other channels, and what are they (number)?

It looks like FM Ingress, which you would be seeing full-time on channels 95-97 (which are the same frequency as 88-108 MHz FM Radio).
If you see something like that on other channels, especially if intermittent, it may be from 2-way radio...you'll see it come and go as they key their transmitter to talk.

If you see it across many channels, especially if you see vertical lines (the "edges" of some other channels' frames, it might be intermodulation from an amplifier being overloaded. But, if you don't have any amps in your home, then it would have to be a problem with the Cable company's "Line Extender" amplifier...you'd see the same effect on all your sets in analog mode.

So, probably a bad shield connection on the line between the tap and splitter. Or, you may be located very close to the transmitter that is interfering.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
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post #5 of 7 Old 05-15-2010, 04:05 PM
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His cross-post can be found here. A couple of the suggestions given there were replace the pre-molded fittings and the lines look like impedance mismatch.

CIAO!

Ed N.
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post #6 of 7 Old 05-15-2010, 05:28 PM
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Looks like RF crap from your Mac (computers generate some powerful interference) getting into the tuner. You can easily eliminate the splitter as the culprit by simply swapping the legs. Check that all your coax connections are clean and tight. Maybe try a different USB port and cable.
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post #7 of 7 Old 05-23-2010, 10:49 AM
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why not just use an unbalanced 3-way splitter? it will clean up your wires big time.

modem goes on 3.5 db leg

WirelessMechanic at your service.
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