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recommended signal levels for SB6183

1: Your location. city, state, zip. Single or multi family complex. :
Fuquay Varina, NC, 27526 - single family home

2: Services you get from TWC :
Internet Only

3: Make and model of modem :
Arris SB6183

4: Make and model of router(s)
Linksys WRT-1900ACs

5: What are your purchased speeds?
50MB Down / 5MB Up

6: What are results from Spectrum speed test. down, up, ping, jitter?
70.9 Down / 5.4 Up

7: Modem's signal, downstream and upstream, and event log pages.
see attached screenshot
8: Description of your cable wiring from street and throughout house, include splitters, devices, cable type (rg6, rg59) and age, etc. and specifically the where the modem attaches.
comming out of the ground block, directly into the modem with RG6, no splitter.

9: Run pathping (windows command) targeting a site that demonstrates problem, preferably one that is pingable, like rr.com. If pathping is not available as command execute tracert. (Linux command istraceroute)
ping and speeds look fine with normal internet traffic, however.. when i Play World of Warcraft, occasionally the connection becomes very jitter, almost intermiitten but it never looses connectivity.
I am trying to diagnose the issue to see if it may be my computer, game addons, or my internet connection, to which i cannot seem to find an issue with my system or game setup, and the only way to resolve
the issue is to reset the cable modem, and just the modem. I have tried various methods of resetting computer.. resetting router, and resetting modem, and neither the computer or router have any impact on
the poor performance, the issue seems to be with either the modem itself or my internet connection.

10: Are any background tasks running that upload or download data automatically, e.g., backup programs, torrent client, file/photo/music sync, auto program/app update, etc.?
none

 

 

I do not have a screenshot of the correctables/uncorrected because i recently reset my modem, and i forgot to take it with the multiple issues listed, but after a few days, maybe a week it will fill up with errors.  i do not know if these levels are at the threshold of being good or bad. according to the MFG website the ideal levels for power it shows being within the maximum values (-15/+15 dbm) but coule possibly be out of spec with ISP which could cause problems, and the only time i really have problems is when i play world of warcraft

 

 

SB6183.PNG

2 REPLIES 2
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Proven Sharer

Re: recommended signal levels for SB6183

Both the upstream and downstream levels recorded by your modem appear to be acceptable.  The manufactturer's spec of +15 to -15 is valid only when there is only one device on the cable.  Folks supporting the forums prefer to see every channel running at -8.0 to +10.0, and showing a SNR of no less than 37 dB.  Outside thoses ranges you can expect high ping times, intermittent glitches, and occasional dropped connections. 

The corrected and especially the uncorrectible packet errors are also important nuumbers.  Here a lower number is always better.  In general the uncorrectibles should not be over a couple thousand for an entire month, and less than 10% of the corrected error count.  These usually appear whenever outside signals leak into the cable system and corrupt the internet data traffic.

Spectrum Employee

Re: recommended signal levels for SB6183


@karlbeckman wrote:

Both the upstream and downstream levels recorded by your modem appear to be acceptable.  The manufactturer's spec of +15 to -15 is valid only when there is only one device on the cable.  Folks supporting the forums prefer to see every channel running at -8.0 to +10.0, and showing a SNR of no less than 37 dB.  Outside thoses ranges you can expect high ping times, intermittent glitches, and occasional dropped connections. 

The corrected and especially the uncorrectible packet errors are also important nuumbers.  Here a lower number is always better.  In general the uncorrectibles should not be over a couple thousand for an entire month, and less than 10% of the corrected error count.  These usually appear whenever outside signals leak into the cable system and corrupt the internet data traffic.


Fixed:

-10 to +15 dBmV on forward/Rx/downstream is most mfg recommendations, ideally no less than -8 dBmV.

< 52 dBmV on return/Tx/upsteam, ideally less than or equal to 50 dBmV.

 

And this has nothing to do with the number of devices on the coaxial system.

The issue with multiple devices is only if there are too many passive splitters.

You can have dozens of modems as long as there are contentions slots at the CMTS and you are using unity-gain amps so that they all get good & even forward & return levels.

 

 

 


@karlbeckman  

 

To be clear, too high forward/Rx/receive/downstream levels DO NOT cause internet speed issues by itself.  Really.  In order for overpowered receiving signals to cause issues in QAM, the MER has to degrade enough to cause issues, which take a lot more than people think (even techs).  For example, a 40 dB MER at +10 dBmV power will have to be approx a +44 dBmV in order to bring it down to a 36 dB MER.   This +10 dBmV upper bound is a myth when it comes to forward signal power level, I don't know what it keeps being advocated so strongly...

 

However, that said, too low forward/Rx/receive/downstream is very VERY susceptible to noise (to use an analogy, it'd be like whispering).  And too high return/Tx/transmit/upstream causes major internet & VOD & boot-up issues almost every time.  Oh and noise also hurts upstream more, because most noise is lower-frequency AC, which is also where the upstream frequencies are located.

If you want to advocate anything, those two all day every day yes please.
Too low Rx, too high Tx, both are bad; and more simply put are just a weak signal.


The two big things which cause issues on coax are:

1.  Weak RF signal (too high return and/or too low forward)

2. Noise on the line (i.e.: from ingress leakage)

 

The only thing you can really look into yourself as a customer is the RF signal power, which is why it's often brought up.  But really, ingress & egress leakage has just as much of a role to play, if not more in all honesty.

 

Also, SNR (Signal-to-Noise-Ratio) is not a measure of real signal quality, it should be regarded as a sign of something else wrong if it is low and that signal quality is generally clean if it's high.  But it is NOT a genuine measurement of signal quality

The actual measures of signal quality on coaxial are: power level, MER, Pre-BER, Post-BER, group delay, echo, and ICFR.  Power level is most often discussed on these forums, measured in dBmV (where 0 dBmV is the standardized wattage at a reference voltage of 1 mV AC)

My postings on this site are my own, off-the-clock, and don’t necessarily represent TWC’s/Charter's strategies or opinions.