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Robotics
See You On The Dark Side
Premium Member
join:2003-10-23
Louisa, VA

Robotics

Premium Member

[Signals] Are These "OK" Signals?

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For the last 24 hours my downstream speeds have been cut in half.

Took a snapshot of the modem levels and just wondering if they are good, bad, so-so.

My speeds have been great for years. But something has changed big time in the last day or so.

All I would like to know is are the levels good?

Thanks
cheeseman
join:2014-06-19
Palo Alto, CA

cheeseman

Member

Downstream is a bit low (-12 to +12, 0 is ideal).

Upstream is golden (+35 to +52).

Robotics
See You On The Dark Side
Premium Member
join:2003-10-23
Louisa, VA

Robotics

Premium Member

Thank you for your response. I'm gonna wait a day (or two) and see if it somehow corrects itself. If it doesn't I will go ahead and make a call.
Thanks again

Johkal
Cool Cat
MVM
join:2002-11-13
Pennsyltucky

1 recommendation

Johkal to cheeseman

MVM

to cheeseman
said by cheeseman:

Downstream is a bit low (-12 to +12, 0 is ideal).

Huh? You do know that -12 is lower than -7.

Ref: »Comcast High Speed Internet FAQ »What should my Signal Levels be?
ExoticFish
join:2008-08-31
Zebulon, NC

ExoticFish to cheeseman

Member

to cheeseman
Personally I would not recommend an upstream above 50. At that point where I live I begin to see service issues. Of course each place is slightly different but at 52, that leaves basically no room for fluctuations.

And it's actually +10 to -10 IIRC as the recommended downstream signal.

Tobin
join:2003-09-21
Burlingame, CA

Tobin to Robotics

Member

to Robotics
I think CableLabs defines the following for upstream using 64QAM:

One channel = no higher than 57 dBmV
Two channels = no higher than 53 dBmV
Three-four channels = no higher than 51dBmV

For downstream it's technically -15 to +15 dBmV for any amount of channel bonding, but it's probably best to be between -3 to +5 dBmV.

Robotics
See You On The Dark Side
Premium Member
join:2003-10-23
Louisa, VA

2 recommendations

Robotics

Premium Member

Oh lord. Thanks all for the responses...but now I don't know exactly if these are good or not. The responses I think confused me. (but it could be me too)
I'm going to call them later today. My download is normally 20 to 28-30mbps. All weekend they have been 5 to 7mbps. Uploads have been consistently faster than downloads (about 6.85 uploads), so something is wrong.

Thanks again you all

Tobin
join:2003-09-21
Burlingame, CA

Tobin to Robotics

Member

to Robotics
I wouldn't suspect your signal levels if your download/uploads are normally fine. They are within spec. Below those tables should be a counter for correctable/uncorrectable codewords. Can you post a screenshot of that?

Robotics
See You On The Dark Side
Premium Member
join:2003-10-23
Louisa, VA

Robotics

Premium Member

I will when I get home. I just walked into work. I can say the correctable/uncorrectable's were extremely high numbers from what I remember seeing yesterday.

fish23
@68.38.145.x

fish23

Anon

I was once told by a Comcast tech that signal levels have nothing to do with speed.

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

EG

Premium Member

said by fish23 :

I was once told by a Comcast tech that signal levels have nothing to do with speed.

They were wrong. Out of spec signal stats / poor connection quality can result in *packet loss* which can affect speeds.
cheeseman
join:2014-06-19
Palo Alto, CA

cheeseman to Johkal

Member

to Johkal
Yes, I do know that. 0 is ideal, -12 is the bottom. Therefore, it is a bit low, because -12 -7 0.

Johkal
Cool Cat
MVM
join:2002-11-13
Pennsyltucky

Johkal

MVM

Not to split hairs, but your statement was/is still confusing.

Per the FAQ:

-7 dBmV to +7 dBmV "Recommended"
-8 dBmV to -10 dBmV / +8 dBmV to +10 dBmV - "Acceptable"
-11 dBmV to -15 dBmV / +11 dBmV to +15 dBmV - "Maximum"
Lower than -15 dBmV & Higher than +15 dBmV - "Out Of Spec."

-7 is hardly low & -12 is not the bottom.

Robotics
See You On The Dark Side
Premium Member
join:2003-10-23
Louisa, VA

Robotics to Tobin

Premium Member

to Tobin
Click for full size
Here is that screenshot, and sorry I thought it was the uncorrectables that were high in number...but my memory was proved wrong. It was the un-error ones.

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

DarkLogix to fish23

Premium Member

to fish23
said by fish23 :

I was once told by a Comcast tech that signal levels have nothing to do with speed.

correct, though if they are borderline then (which the OP's aren't) then they can go out of sync and losing sync will kill your speed.
DarkLogix

DarkLogix to Johkal

Premium Member

to Johkal
said by Johkal:

-7 is hardly low & -12 is not the bottom.

Well the bottom depends on the modem and if it can "hear" that low.

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

1 recommendation

EG to DarkLogix

Premium Member

to DarkLogix
said by DarkLogix:

correct, though if they are borderline then (which the OP's aren't) then they can go out of sync and losing sync will kill your speed.

Losing sync kills everything no ? Packet loss / bit errors cause slower speeds.

Tobin
join:2003-09-21
Burlingame, CA

Tobin

Member

Your cable modem can drop 'sync' on individually bonded channels, which can lead to reduced available bandwidth and a higher chance of congestion, I guess.

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

EG

Premium Member

FWIW, I was referring to a loss of *block* sync.
VirtualLarry
Premium Member
join:2003-08-01

VirtualLarry to Robotics

Premium Member

to Robotics
I have a 6141, and my service has yet to be activated, but my modem syncs. My upstream power level for two channels is 53. Is that bad, and could it be caused by using a 7.5dbi splitter?

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

DarkLogix

Premium Member

Yes and Yes.
53 upstream is high and likely to have trouble maintaining sync, if the other possible channels have even more attenuation it might be why you're only seeing 2.

Tobin
join:2003-09-21
Burlingame, CA

Tobin to VirtualLarry

Member

to VirtualLarry
You'd be at 46dBmV without the 4-way splitter. I'd rather see low 40s without any splits at all since even a 2-way split puts you at 49.5dBmV
VirtualLarry
Premium Member
join:2003-08-01

VirtualLarry to Robotics

Premium Member

to Robotics
I wasn't sure if I was allowed to run the cable straight from the jack to the modem without a splitter.