Cable modem after a splitter

[SickBeast]

The cable installer had to install a new cable feed from the main line to my house as the existing one was too old. After the install, he said that it gave him too much signal, so he had to install a 3-way splitter to tone it down a bit.

My wife and I have been having problems with making VOIP calls through our line, so I decided to try removing the splitter.

Here are the results from the Motorola diagnostics:

With 7dB loss from splitter:

37.5dB SNR
1.5dB downstream power level
44.2 dBmV upstream power

With 3.5dB loss from splitter:

37.6 SNR
4.5dB downstream power level
41.4dBmV upstream power

With the splitter completely removed:

37.5dB SNR
8.3dB downstream power level
38.2dBmV upstream power

Apparently the downstream power level should be within -8 to +8dB. The thing is, my internet speed improved quite a bit by removing the splitter! Do I need to worry about damaging my hardware due to "too much" power?

Thanks! :beer:

 

[ScottMac]

Not at the levels you are showing. It might still be advisable to put in an attenuator to drop the levels a bit to avoid distortion issues.

The cable guy should have had some. Attenuators are preferred over a dead-end splitter because it's electrically neutral and not likely to introduce noise like an unterminated splitter.

You can get attenuators at Rat Shack for a couple bucks each, usually available in values of 3dB, incrementing by 3dB. I'd say, put in a 3 and see how things go.

 

[imagoon]

@8.3 I wouldn't even care to be honest. When I was on Comcast (hell) my downstream was 18.8 and it 'worked'. Your going to run in to issues with upstream noise at the level your at though for that. 45-50dBmV was about the point my service would start to get very iffy. The problem for me was that I was starting at 38ish like you are but in order to get the signal "down" my upstream would degrade to crap.

edit

They need to adjust the tap to lower the output signal. Good luck...

 

[SickBeast]

Awesome; thanks for the info, guys.

imagoon, are you saying that 38dBmV is bad for my upstream power? Should it be lower or higher? If I lower the downstream power, the upstream power seems to increase. I was under the impression that 40dBmV is optimal for the upstream power.

Thanks. :beer:

 

[Modelworks]

I'm surprised he used a splitter instead of a attenuator. Sounds like he was just looking to do a quick fix.
Nothing about cable surprises me anymore. I can get cable tv channels from an outside antenna because the company has the local distribution node turned up 100X.

 

[kevnich2]

Originally posted by: Modelworks
I'm surprised he used a splitter instead of a attenuator. Sounds like he was just looking to do a quick fix.
Nothing about cable surprises me anymore. I can get cable tv channels from an outside antenna because the company has the local distribution node turned up 100X.

Yeah cable technology is good, as long as the greedy cable companies don't overuse things. I typically see nodes at 90-95% capacity during normal hours and then during busy hours, haha, forget about even trying to use the internet. If they'd actually keep things at a reasonable level and use the money they get to actually re-invest in their network, cable would be awesome all over the place.

 

[ScottMac]

Originally posted by: Modelworks
I'm surprised he used a splitter instead of a attenuator. Sounds like he was just looking to do a quick fix.
Nothing about cable surprises me anymore. I can get cable tv channels from an outside antenna because the company has the local distribution node turned up 100X.

If you really can, they should be reported; some of those frequencies interfere with air traffic navigation and are considered a hazard.

 

[Modelworks]

Originally posted by: ScottMac

Originally posted by: Modelworks
I'm surprised he used a splitter instead of a attenuator. Sounds like he was just looking to do a quick fix.
Nothing about cable surprises me anymore. I can get cable tv channels from an outside antenna because the company has the local distribution node turned up 100X.

If you really can, they should be reported; some of those frequencies interfere with air traffic navigation and are considered a hazard.

I can, and they are about 75% without snow. The antenna is about 60ft from the node. Found out about it when a channel 8 appeared on my tv when I knew there was no channel 8 locally, especially not WGN Chicago.

 

[ScottMac]

Well, then give them a call and explain that if it doesn't go away in a week, you'll call the FAA (it really does interfere with navigation, it's considered a safety hazard to aircraft), the FAA will call the FCC, who will investigate, then the FCC calls the cable company and will begin to fine them (tens of thousands of dollars a day) after some fairly short period of time.

That's the way it's supposed to work, YMMV.

 

[imagoon]

Originally posted by: SickBeast
Awesome; thanks for the info, guys.

imagoon, are you saying that 38dBmV is bad for my upstream power? Should it be lower or higher? If I lower the downstream power, the upstream power seems to increase. I was under the impression that 40dBmV is optimal for the upstream power.

Thanks. :beer:

The upstream signal is the reverse of the downstream. Downstream = signal to noise while upstream is the "amount of signal" being sent. You often can't get the upstream signal to noise since the node would produce the number and your modem can't access the node's data. So. In upstream, lower power is generally better because it indicates that less of the signal is getting lost on the way back to the node. When the node's SNR gets bad, it will tell your modem to up the signal to try and lower the SNR. (ie in very bad example: 10 signal, 5 noise= 10:5 or 2:1, if the modem needed more signal, it might request 20 so 20:5 or 4:1 since the noise generally stays the same assuming nothing else changes.)

Open connections on splitters will basically bleed the upstream signal to the air. So the modem has to push more because it is basically powering antennas as well as the cable.

For me 50ish was about the time that the connection just started failing period. This can vary depending on the upkeep of the system around you. I had the disadvantage of living next to apartments where most of the tenants apparently felt they shouldn't need to pay for cable and while trying to steal it, they would often break the tap off trying to remove the security nut. Modelworks might be picking up something like that actually =). Once the tap is broken off it acts like a broadcast antenna, wrecking internet upstream and downstream.

This mess often would leave me with having what I think to this day is still my record "ping" of 8345ms round trip to google.com.

 

[SickBeast]

Great, thanks for the info, imagoon. :beer:

I'm going to just run my setup with no attenuator and no splitter, just the cable.

I got over 800Kb/sec downloading a Linux torrent today so I'm happy with it seeing as my provider sold me 7mb/sec service (I'm basically hitting the theoretical maximum which is great).