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Low Upstream Power T25

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Regular Visitor

Low Upstream Power T25

Hi all, I've had a number of events where my T25 has stopped responding and has had to be manually rebooted, or where I've had a spontaneous reboot. The downstream power levels seem to fine (at least according to to the Touchstone support page) but I do seem to be getting quite a few Correcteds/Uncorrectables although not sure if the volume is high enough to worry about. Dowstream QAM power levels don't seem to be in spec and Touchstone suggest +45 to +51 ? 

 

Could the low up power be the cause of my drop outs and any suggestions for correcting. Thanks in advance for any help.

 

Upstream and downstream QAM as follows:

Upstream QAM

 UCIDFreqPowerChannel TypeSymbol RateModulation
Upstream 1623.70 MHz41.00 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 2836.50 MHz41.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 3730.10 MHz41.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 4517.30 MHz41.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM

 

Downstream QAM

 DCIDFreqPowerSNRModulationOctetsCorrectedsUncorrectables
Downstream 16459.00 MHz-8.10 dBmV37.64 dB256QAM7505330200
Downstream 27465.00 MHz-7.90 dBmV38.61 dB256QAM1402072800
Downstream 38471.00 MHz-7.90 dBmV38.61 dB256QAM1346792400
Downstream 49477.00 MHz-7.60 dBmV38.61 dB256QAM7094069600
Downstream 510483.00 MHz-7.60 dBmV38.61 dB256QAM7073432800
Downstream 611489.00 MHz-7.40 dBmV38.61 dB256QAM1076248600
Downstream 712495.00 MHz-7.20 dBmV38.61 dB256QAM1158852600
Downstream 813519.00 MHz-7.80 dBmV37.36 dB256QAM779143640
Downstream 914525.00 MHz-9.40 dBmV37.36 dB256QAM981092600
Downstream 1015531.00 MHz-10.20 dBmV37.36 dB256QAM790455400
Downstream 1116537.00 MHz-10.10 dBmV37.36 dB256QAM751027300
Downstream 1217543.00 MHz-9.90 dBmV37.36 dB256QAM1052708020
Downstream 1318549.00 MHz-10.00 dBmV37.64 dB256QAM1024351020
Downstream 1419555.00 MHz-9.50 dBmV37.64 dB256QAM1028832600
Downstream 1520561.00 MHz-9.00 dBmV37.36 dB256QAM1019656200
Downstream 1621567.00 MHz-8.80 dBmV37.64 dB256QAM852923000
Downstream 1722573.00 MHz-8.50 dBmV38.61 dB256QAM6781362100
Downstream 1823579.00 MHz-8.50 dBmV37.64 dB256QAM1026634520
Downstream 1924585.00 MHz-8.70 dBmV37.64 dB256QAM947270800
Downstream 2025591.00 MHz-8.70 dBmV38.61 dB256QAM978286500
Downstream 2126597.00 MHz-8.50 dBmV38.61 dB256QAM1024601000
Downstream 2227603.00 MHz-8.20 dBmV38.61 dB256QAM1091906000
Downstream 2328609.00 MHz-7.90 dBmV38.98 dB256QAM1147199000
Downstream 2429615.00 MHz-7.70 dBmV38.61 dB256QAM7533908490
Downstream 2530621.00 MHz-7.70 dBmV38.98 dB256QAM790205430
Downstream 2631627.00 MHz-7.90 dBmV38.61 dB256QAM7975279680
Downstream 2732633.00 MHz-7.80 dBmV38.98 dB256QAM14697364260
Downstream 2834639.00 MHz-7.90 dBmV38.61 dB256QAM165423263951
Downstream 2935645.00 MHz-7.60 dBmV38.98 dB256QAM1578440720
Downstream 3036651.00 MHz-7.80 dBmV38.61 dB256QAM1512688200
Downstream 3137657.00 MHz-7.90 dBmV38.61 dB256QAM151676152

0

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Diamond Problem Solver

Re: Low Upstream Power T25

It’s your downstream that’s low, upstream is good

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Expert

Re: Low Upstream Power T25

Couldn't agree more with @ComcastAndrew !! FWIW, Arris is wrong ! They have been passing the buck and have been conning people with that statement lately !! Only the Comcast plant / engineering specs matter;

 

Specification Min Max
Downstream Power Level
Cable Modems -10dBmV +10dBmV
Gateways and EMTAs -7dBmV +7dBmV
Downstream Signal to Noise Ratio 35dB -
Upstream Power Level +35dBmV +50dBmV
Upstream Signal to Noise Ratio 31dB -
Upstream Receive Power -2dBmV
+2dBmV



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Expert

Re: Low Upstream Power T25

Stuff that you can try;

 

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.



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Regular Visitor

Re: Low Upstream Power T25

Thank you both. As suggested I've ordered a two way splitter and I'll also try swaping out the cable from the splitter to the modem. Hopefully his means I won't have to work with the service guys.

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Diamond Problem Solver

Re: Low Upstream Power T25

Take the levels again at your point of entry so you have something to compare with. To give you an idea of outside vs inside

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