Strange power levels: cause?

[lairdjnelson]

If my understanding is right, the power levels and other numbers here are way out of whack.  What could be the cause of this?

(I have cabling installed by Comcast entering the house, entering a MoCA PoE filter, entering a Comcast supplied and installed two-way splitter, attached to house cable, attached to two-way Comcast supplied and installed two-way splitter, attached to Comcast cabling attached to a Comcast gateway.  Total db loss due to splitters is 3.5 X 2 = 7.  MoCA is active.)

Downstream	Channel Bonding Value
Index	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24
Lock Status	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked	Locked
Frequency	513 MHz	459 MHz	465 MHz	471 MHz	477 MHz	483 MHz	489 MHz	495 MHz	507 MHz	519 MHz	525 MHz	531 MHz	543 MHz	549 MHz	555 MHz	561 MHz	567 MHz	573 MHz	579 MHz	585 MHz	591 MHz	597 MHz	603 MHz	609 MHz
SNR	32.237 dB	30.885 dB	29.759 dB	28.062 dB	27.607 dB	30.002 dB	31.915 dB	33.377 dB	32.963 dB	31.994 dB	32.237 dB	33.487 dB	35.084 dB	35.595 dB	34.926 dB	33.957 dB	34.346 dB	33.957 dB	34.484 dB	35.084 dB	35.595 dB	35.595 dB	35.084 dB	34.926 dB
Power Level	-18.700 dBmV	-20.800 dBmV	-22.100 dBmV	-24.100 dBmV	-24.600 dBmV	-21.600 dBmV	-19.100 dBmV	-17.400 dBmV	-17.300 dBmV	-19.100 dBmV	-18.500 dBmV	-16.700 dBmV	-13.500 dBmV	-13.200 dBmV	-14.400 dBmV	-15.300 dBmV	-15.100 dBmV	-15.500 dBmV	-14.300 dBmV	-12.700 dBmV	-11.700 dBmV	-12.000 dBmV	-12.600 dBmV	-13.100 dBmV
Modulation	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM	256 QAM

[lairdjnelson]

I'm using https://pickmymodem.com/signal-levels-docsis-3-03-1-cable-modem/ to discern what is "out of whack" and what is not.

[EG]

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.

[lairdjnelson]

Thanks for your reply.  The splitters I documented are the only ones, and they were supplied by Comcast.  Sadly, I can't drop down to one splitter.

Do you have any wisdom to impart on the power levels in particular?  To my naïve eyes it looks like they're too hot, not too low.

[EG]

The downstream power is way too low ! So are the SNR's. You didn't post the upstream power levels.

[lairdjnelson]

Ah!  OK, I'm glad I asked, and thanks again for your reply.

Here's the rest of what I didn't post originally (sorry about that):

Upstream	Channel Bonding Value
Index	1
Lock Status	Not Locked
Frequency	9 MHz
Symbol Rate	5120 KSym/sec
Power Level	57.000 dBmV
Modulation	64 QAM
Channel Type	ATDMA

CM Error Codewords
Unerrored Codewords	2809626032	2805395047	2804831994	2540852341	1932508948	2805129755	2805389668	2805346925	2805390008	2805389951	2805384624	2805365019	2805336849	2805364486	2805361727	2805353133	2805342599	2805340987	2805334956	2805461320	2805455658	2805447904	2805443313	2805430375
Correctable Codewords	4358	25997	588032	180682182	788336829	272541	5944	40451	3288	3662	3132	1462	177	88	114	156	108	156	61	33	43	41	41	44
Uncorrectable Codewords	1079	1185	1237	1390944	2154537	1071	953	1165	946	1043	1017	1040	31	28	28	27	32	25	24	28	0	0	1	0

[lairdjnelson]

Let me ask you this, if I may: is low power due to the splitters (I've certainly been in places where there have been lots more splitters involved!), or more likely due to cable run?  (From the outside of the house, the cable cuts across a garage bay and into a combination furnace/telecom room.  Not very long, but what do I know?)

There are no unterminated jacks or anything like that, so no place (under my control) for noise to "leak" in to the circuit.

(I hesitate to get a tech out because usually they're under time pressure so they just swap out the cables the previous tech has installed and leave.  I understand that bang for the buck wise this probably is a quick way to get many problems fixed, but in this case I strongly believe something else is up.)

[EG]

It could be. The more splitters that are cascaded, the more the loss. It especially a problem if the incoming signal from the street / pole is already too weak.

And the upstream power it WAY out of spec too ! So much so that you've lost the bonding of the multiple channels....

[EG · Accepted solution]

You need a tech out to investigate as was stated earlier. Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home. Good luck with it !