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

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

Click for full size
I ask because I was having random disconnects with the old modem on Performance tier (Arris 602). I am hoping it was a modem problem and not a signal problem. So... here is what I have now on the 722G.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4

1 recommendation

could be better....-8/51 isnt what i would strive for....if you can bypass one splitter it would have much more favorable signal....and might clear up some of those downstream eerors your counters are showing.
--
I'm better than you!


JigglyWiggly

join:2009-07-12
Pleasanton, CA
reply to owlyn
gross
i mean it will work
but it's not pretty


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast
reply to gar187er
Can't really remove a splitter. There are only two, and there's only one that could even remotely be a candidate for removal, but that would leave the guest room without TV. I suppose I could remove it and replace it with a barrel until we need the room, but it would be a pain. It's working, so I guess I'll let it be. If I drop back to the Perfomance tier, would the numbers get better or stay the same?

JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5
Ideally, and especially with those levels, you want two splitters. A 2 port at the main incoming line with one port feeding the modem and the other port feeding the next splitter. The next splitter will be as large as need be for your TV outlets.

Assuming you have a 4 port or so splitter, you are likely losing ~7 dB if not more since this is on a second splitter that is likely after the first. By putting the modem on a 2 port first you could potentially bring those downstream levels up to around 0 dB but the actual figures will depend on what actual splitters you have in place and their respective loss levels (such as a balanced or unbalanced splitter).


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast
Click for full size
said by JoelC707:

Ideally, and especially with those levels, you want two splitters. A 2 port at the main incoming line with one port feeding the modem and the other port feeding the next splitter. The next splitter will be as large as need be for your TV outlets.

Assuming you have a 4 port or so splitter, you are likely losing ~7 dB if not more since this is on a second splitter that is likely after the first. By putting the modem on a 2 port first you could potentially bring those downstream levels up to around 0 dB but the actual figures will depend on what actual splitters you have in place and their respective loss levels (such as a balanced or unbalanced splitter).

Unfortunately, I can't do that. I have an unbalanced three way splitter feeding the various parts of the house. The strongest leg (-3.5db) comes up to the next splitter, which is balanced, and half goes to the modem, the other half to the guest room TV. So my total loss is at the modem is about -7db.

I reset my error counters several hours ago, and things seemed to have settled down. Above are the latest stats (I don't know how to put the picture after the text). The numbers before were the total from the time of install, re-provisioning to Blast, and running a few ShaperProbes. The latest numbers reflect normal surfing, etc. Don't know if any of that makes a difference. I had the tech check my signal levels, and he said everything was good, but who knows... That's why I ask here.

On the up-side, I definitely have native IPV6 now.

andyross
Premium,MVM
join:2003-05-04
Schaumburg, IL
reply to owlyn
For 3-upstream bonding, the limits are 51 for 64QAM and 52 for 16QAM. You are at those limits and could have issues.


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

1 edit
As of this morning, I was back to one upstream 64QAM.


fonzbear2000
Premium
join:2005-08-09
Saint Paul, MN
How are your speeds? If those are fast enough, there's probably not too much to worry about.
--
»Music2pc-This program is AMAZING!


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast
Funny you should ask. Just finished:

Speedtest.net: 52.91 down, 10.27 up, ping 13

Shaperprobe:

DiffProbe release. January 2012. Build 1008.
Shaper Detection Module.

Connected to server 72.26.217.87.

Estimating capacity:
Upstream: 10756 Kbps.
Downstream: 94301 Kbps.

The measurement will take upto 2.5 minutes. Please wait.

Checking for traffic shapers:

Upstream: No shaper detected.
Median received rate: 10528 Kbps.

Downstream: No shaper detected.
Median received rate: 52453 Kbps.

Guess I shouldn't worry about it...

Oedipus

join:2005-05-09
kudos:1
reply to owlyn
OP's signals are almost identical to mine, and I have a similar modem (702G vs 722G.) I've never had a problem at these numbers; 62/15 speedtests all day long.


JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:3
Reviews:
·Verizon FiOS
·Comcast
reply to owlyn
Owlyn-
Downstream and SNR are tolerable, but as everyone stated, your upstream is at the limit.

It's most likely why you are dropping bonding - usually there are some exterior issues leading to that high of a level that a line tech could fix.
--
"ONE team - ONE city - ONE dream!!"


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to owlyn
Put the CM on the 3.5 leg, and put whatever splitters you need on the others.


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

Put the CM on the 3.5 leg, and put whatever splitters you need on the others.

I can't without rewiring.


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
reply to JeepMatt
Jeepmatt

Thanks. My speeds are good for now, so I may just wait to see what happens.


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
reply to JeepMatt
Ignore this post.

JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5
reply to owlyn
You would only gain approximately 3.5 dB anyway. It may be that little bit that makes the difference though. I do understand wiring issues. The house I lived in out in Tucson was a mess. All the cable lines ran across the roof (yeah, up and over in hot Tucson sun) and it looked like the original installer used scraps as every run had at least 1 if not 2 barrels in it.

Maybe they just had a LOT of accidents up there and damaged nearly every cable run in different spots but I'm leaning towards using up scraps instead. Maybe it was the homeowner instead? Shrug, I was renting so I did what I could to clean it up and keep my levels decent.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to owlyn
said by owlyn:

said by DarkLogix:

Put the CM on the 3.5 leg, and put whatever splitters you need on the others.

I can't without rewiring.

Well looks like some re-wiring is needed then


flwpwr

@comcast.net
reply to andyross
said by andyross:

For 3-upstream bonding, the limits are 51 for 64QAM and 52 for 16QAM. You are at those limits and could have issues.

This is wrong.

»[Connectivity] Intermittent connectivity - upload power @54 dBmV

That said we can pretty much forget about qam 16 versus 64, as the qam 16 carriers can now be bonded with 64 carriers in D3 bonding, so the reality in the physical world is

54 for it all, and the company wants 51 so they have play room so when the cable goes from 45F to 85F temperature wise in the day, it can gain a little return and the modems stay on line. No one calls in and says my return is 53 I need a service call, instead they call in when the modem goes off line. Let me correct that none that's normal, we have some loons at this board who have called in for return values, but.. I am pretty sure they got nothing out of it. That's the way cable works things are dynamic not static out there in the physical world, one minute its 85 degrees and blistering sunny, the next its 55 and raining, pulling all the heat out of any objects it hits, and when that happens, things contract and expand as mother nature intended them to do. Same with your computer when you turn it on and off, which is why there is the decades old debate about whether its better to leave it on all the time or not. Which is about equivalent in importance to the "are my signals ok" after an install that is working.

andyross
Premium,MVM
join:2003-05-04
Schaumburg, IL
This is in the actual specs that were posted awhile ago. 54dB is the limit for 2-channel bonding, and 51 for 3 or 4-channel. For 16QAM, add 1dB.


owlyn
Premium,MVM
join:2004-06-05
Newtown, PA
Reviews:
·Comcast
Click for full size
Latest Stats
My latest stats.


JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:3
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:10
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.