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owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast
reply to andyross

Re: [Connectivity] Just Got Blast - How Are My Levels?

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Latest Stats
My latest stats.


JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:2
Reviews:
·Verizon FiOS
·Comcast

Yeah, even the DL levels are off. You shouldn't see such a variance between bonded channels (at least that's what is preferred).

Downstream 1 3 663.00 MHz 8.30 dBmV 35.97 dB
Downstream 2 4 669.00 MHz 8.30 dBmV 36.61 dB
Downstream 3 5 675.00 MHz 8.16 dBmV 36.17 dB
Downstream 4 6 681.00 MHz 8.07 dBmV 36.39 dB

Upstream 1 10 36.20 MHz 47.75 dBmV 64QAM
Upstream 3 11 29.40 MHz 47.00 dBmV 64QAM
Upstream 4 12 22.00 MHz 46.00 dBmV 16QAM

Here's what I have (and yes, everyone including me and tech knew my signals were "hot")..
--
"ONE team - ONE city - ONE dream!!"



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA

JeepMatt,

So what would cause the variance in my bonded channels?



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

Click for full size
Better Levels
I may have figured out why my levels were so poor. This screen shot shows better levels than before (see earlier shots in this thread).

Some additional background:

A few weeks ago, we had a series of bad storms that caused many power failures. All of my equipment is on a UPS, so I had all clean shutdowns. One power failure was pretty severe- a power company transformer blew a fuse, taking out Comcast as well as our power. A few hours later, power was restored, and the Comcast tech was right on the heels of the power company guys. Comcast service was restored within 30 minutes of the power. This is when my problems began (not exactly the level issue, but I'll get to that).

I had the Performance tier (15/2) with an Arris 602G modem (Docsis 2) and I started having frequent intermittent disconnects that would last anywhere from a few minutes to a half hour, and occasionally a couple of hours. I suspected a signal issue, but for some reason (TV worked fine, speeds were good when the modem was up), I thought it was the modem. I couldn't convince Comcast to send someone out with a new modem. I wanted Docsis 3 anyway, as well as a desire to see the admin pages, and get native IPV6, so I decided to do the upgrade to Blast for $10/month, figuring once I had the Docsis 3 modem, and got everythging running properly I would downgrade back to performance, and still have the Docsis 3 modem.

Well, as you know, the levels on my new modem were just barely okay. I would lose the 3 bonded US channels and get them back again, then lose them... Things were generally okay, but I would see the occasional very brief disconnects (about 30 seconds long). This happened a few times over the last 5 days. Today I got a 2 hour disconnect. After it reconnected, I saw that I lost the bonded US channels again. My levels were not great- a tad worse than before, but I guess enough to put it over the edge.

So, now I know it isn't the modem- it must be a signal issue. Checked all my splitters and connections- all okay. Then, while I was exercising on the treadmill, it hit me-

I am running the line to my modem through the UPS (an APC XS1500, if anyone cares). I thought that with all the activity due to the power failure, perhaps something was wrong. Also, during one of the power failures, I saw that the UPS was still getting 4 volts coming in. Anyway... I bypassed the UPS, running the line directly to the modem. When it came back up, I had my 3 bonded US channels again, and better levels (see screen shot, and compare to previous ones in this thread). Also note that there are now no errors (I even ran a a Shaperprobe test, as that had always produced errors before).

So, what do you all think? Might I have nailed it, or is it just coincidence?

Thanks for your help and input.

Oedipus

join:2005-05-09
kudos:1
reply to owlyn

Your upstream is still high, so you may continue to see problems. If you're feeling adventurous, test your signal levels at the demarc on the side of your house. At least then you'll know how badly your internal wiring is affecting your results.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

said by Oedipus:

Your upstream is still high, so you may continue to see problems. If you're feeling adventurous, test your signal levels at the demarc on the side of your house. At least then you'll know how badly your internal wiring is affecting your results.

How would I do that? Move the modem down to the demarc, and connect it to my laptop so I can read the page?

Oedipus

join:2005-05-09
kudos:1
reply to owlyn

Yes.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

I just had Comcast check my US SNR levels. They are supposedly fine: about 36-37 DB, which happens to match my DS SNR levels.
They said the graph shows bad levels and multiple disconnects prior to my rerouting the cable. From the time I rerouted and onward the levels look good, so I am keeping my fingers crossed.

Any additional comments are appreciated.

Again, thanks.



EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

They probably gave you the downstream SNR figure from your modem.. Not surprising... Try to get a phone rep that knows the right tool to use to poll the CMTS.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

Click for full size
Levels With Bi-Directional Amp
Update:

Each day since my last post, the service has been fairly stable. No disconnects, but each day, I'd come home from work to find that I'd lost my upstream bonded channels, leaving only one. Speeds were still fine at 50/10. The US signal level was correspondingly high (53, which appears to be the maximum point for my bonded US channels). I would then either reset the modem, or disconnect the coax and reconnect it, and I'd get the US bonded channels again, with the barely okay levels (50-53) I've had in earlier screen shots. Maybe sometimes as low as 49.25 on the lowest frequency DS channel.

So, I thought I'd try an experiment. I had an unused bidirectional amplifier laying around, so I connected it just before the modem (not the optimal place, as this was after two splitters, but it was just an experiment to see if it did anything at all). The amp is adjustable to +8db, which is where I _think_ I have it (maxed the knob clockwise).

Well, I got results, as shown in the screen shot. You can compare these levels to previous screen shots earlier in this thread. The reported levels are now better, and I guess when I get home from work tomorrow, I'll see if anything got dropped. And, BTW, I also ran the coax back into my UPS. This did degrade the levels a bit, but the results shown include the path through the UPS.

In the meantime, my question is this: Is the amp actually doing anything useful, or is it just skewing the results on the modem? IOW, is this basically what Comcast would have done to rectify the problem (adjust an amp or put an amp in the line somewhere), or is it just an illusion?

One other thing- the battery telemetry starts out as normal, but after about 24 hours, switches to "Battery Test In Progress", and never goes away until I pull and replace the battery. Whats up with that?

Thanks.

Oedipus

join:2005-05-09
kudos:1
reply to owlyn

I've never seen someone recommend amping a modem, ever.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

said by Oedipus:

I've never seen someone recommend amping a modem, ever.

Okay, but that doesn't answer my question.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3

No its not what comcast would have done.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA

Okay, but what would Comcast do to fix the problem?


JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

First, they would actually check your levels at the tap and the ground block. If you have good signal there they would possibly rewire things in the house as we have suggested (likely for a fee) or tell you to fix it. If you have marginal signal levels there, it would likely take involvement of the engineering crew to rebalance the system to get you higher signal at the tap (change tap faces, turn up amps, whatever).

An amp normally doesn't touch the return path but it seems this one might. In any case an amp amplifies everything; garbage in, amplified garbage out. An amp can work if you have clean signal coming in but simply need to split it a lot, what is often put in there is a powered splitter (basically an amp with a splitter), but it would be the first thing on the line coming into the house, not at the modem.

Either way, before just throwing an amp at it you need to know what you have coming in, which is where you need to take the modem out to the ground block and either a laptop or long ethernet cord back to the desktop. You need to know what you have coming in before you can really make any decisions about what will or won't work. Unless the drop is especially long or damaged, what you see at the ground block will likely be within a dB or two of what you would see at the tap.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

Thanks. The problems started after Comcast did some repar work at a box on the street, so things may not be balanced properly. My modem is behind two splitters for a total splitter loss of 7db. I will take the modem and other necessary gear to my side of the demark and see what it reports for level there. The amp is a bidirectional amp with built in splitters, so I could move it so it replaces the first splitter. Then my modem would be behind the amp and one splitter.


JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

The ideal placement of that amp would be replacing all the splitters and have every outlet run directly to it, though I know that may not be possible without rewiring. Definitely let us know the levels at the ground block.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

Joel,

Thanks. I know I need to move the modem- I it was just a quick experiment to see if there would be any change at all. And, yes, unfortunately, it would mean rewiring if I wanted to do a home run from the amp to the modem. At least there will only be one splitter in the way. I'll post my levels from the demark once I get them.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

1 edit
reply to JoelC707

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After Amp and One Splitter
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At My Side of the Demark
To recap:

At the top of this thread are my modem signal levels after two splitters representing a total loss of -7.5 db. I was getting intermittent disconnects with that configuration, and that was the reason I originally posted.

I then added an bidirectional amp that has a built-in 4 way splitter. Levels looked decent, but I was asked to show the levels on my side of the demark, without the amp, and before any splitters.

I just did the levels at the demark test. Two results are shown. The first one is after the amp and one splitter (my new "normal" configuration). The second one is at my side of the demark. The DS Levels at the demark look high to me. No problem with the amp configuration so far.

I am using three of the legs of the amp. Two go directly to cable boxes. The third goes to a balanced (-3.5db/leg) two way splitter. One leg of that feeds the modem, the other, a cable box.

Comments, please. Thanks.

JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

So we have a big spread in downstream power at the demarc but that's not too bad. Upstream is actually pretty good here, much better than what you had a few days ago before the amp. What concerns me is the amount of signal you are "losing" in your house.

Downstream Channels:
1: 5.81 - (-4.64) = 10.45
2: 6.16 - (-5.65) = 11.81
3: 7.01 - (-2.69) = 9.7
4: 10.59 - 1.19 = 9.4

You're losing roughly 10+ dB from your inside wiring and/or splitters, that's a LOT to lose since the modem is now on a single 3.5dB leg after a powered splitter/amp. The only way I would see that loss as acceptable is if you have a ~100 foot run inside the house after the amp or maybe even going back to the ground block.

RG6 loses about 6.5 dB at 1000 MHz at 100 feet (you're operating at 650-700 MHz so your loss will be a little less than that), with RG59 you're up to about 11 dB loss. Actual loss for either will depend on the actual type of cable (center conductor type and size as well as shield construction).

I don't recall if you mentioned in the thread anywhere whether your runs are RG6 or RG59? If they are RG59 that is your problem and it needs to be replaced. If it's RG6 and especially if it's less than a 100 foot run (I'd suspect it is), then you might have damage somewhere. Either way the proper fix is still going to be doing what you don't want to do, rewiring. Can you access the run(s) along the entire path to check for damage?



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

2 edits

Everything is behind walls. There is no access except at the wall plates. I'm not sure, but I think it's RG59. Looks too thin to be 6. The run could be 100 feet, but I doubt it.

I could have Comcast create a separate run from the demark outside the house, behind a downspout, and into the room where the modem is. But, is there any problem just leaving the amp in place? So far, everything seems to be working with the amp in place (I'll know better on the next really hot day). The only problem I can see is if there is a power failure, I would lose phone and internet because the amp lost power, but I could get a barrel connector to use in such an emergency, and connect the incoming line from the demark directly to the line that goes to the modem. This would eliminate one -3.5 db splitter, and should be okay. Won't be able to watch TV anyway...


JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

I wouldn't normally recommend this but I'm going to say run with the amp for a while. It doesn't really seem to be doing anything bad so leave it in and see what happens.



owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast

said by JoelC707:

I wouldn't normally recommend this but I'm going to say run with the amp for a while. It doesn't really seem to be doing anything bad so leave it in and see what happens.

Thanks. Unless someone makes a convincing argument otherwise, I'm inclined to leave it be. TVs are all working fine, too. I tried putting a 75 ohm terminator on the open port on the amp, but it made my levels worse, so I removed it. Don't understand why that would happen, but whatever works...

I also am not running the coax through the UPS, as all that did was degrade the signal further. Any lightning surges coming in on the coax should be caught at the ground block anyway (one hopes).