MB8600 - Millions of uncorrected errors, low signal to noise ratio (SNR), slow gigabit

Can you hook up your modem at the point of entry (to bypass your house wiring), and see if your levels change? If not, you’ll need a tech out to troubleshoot outside

Hi @CCAndrew, thank you for the reply!

 

I don't know how to hook up my modem at the point of entry (to bypass my house wiring). Do you have any guidance on how to do that?

Some things that you can try before getting a tech visit;

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.

 

Good luck with it !

Hi @EG and @CCAndrew -  thank you very much to both of you. You helped me solve my problem!

 

How I fixed my problem - short version

 

As both @CCAndrew and @EG said:

I connected the cable inside my house to my modem before it hit any splitters and my problems disappeared.

 

 

How I fixed my problem - long version

 

After I followed this advice from @CCAndrew :

"Try to find the ground block or the cable inside before it hits any splitters. Hook that cable up to your modem and power it up, read your levels just like you did above."

 

And this advice from @EG :

"...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..."

 

I got the following readings from my Mororola MB8600:

 

Downstream Bonded Channels

 

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB )	Corrected	Uncorrected
1	Locked	QAM256	36	645.0	-2.0	39.6	0	0
2	Locked	QAM256	8	471.0	-4.1	39.5	0	0
3	Locked	QAM256	9	477.0	-3.5	39.6	0	0
4	Locked	QAM256	10	483.0	-2.1	40.2	0	0
5	Locked	QAM256	11	489.0	-1.7	40.1	0	0
6	Locked	QAM256	12	495.0	-2.5	39.6	0	0
7	Locked	QAM256	13	507.0	-2.8	39.7	0	0
8	Locked	QAM256	14	513.0	-1.9	40.1	0	0
9	Locked	QAM256	15	519.0	-2.1	39.9	0	0
10	Locked	QAM256	16	525.0	-2.9	39.7	0	0
11	Locked	QAM256	17	531.0	-2.6	39.7	0	0
12	Locked	QAM256	18	537.0	-1.6	39.8	0	0
13	Locked	QAM256	19	543.0	-1.8	39.9	0	0
14	Locked	QAM256	20	549.0	-2.4	39.7	0	0
15	Locked	QAM256	21	555.0	-3.1	39.5	0	0
16	Locked	QAM256	22	561.0	-2.2	39.7	0	0
17	Locked	QAM256	23	567.0	-1.4	39.7	0	0
18	Locked	QAM256	24	573.0	-1.9	39.4	0	0
19	Locked	QAM256	25	579.0	-2.3	39.5	0	0
20	Locked	QAM256	26	585.0	-2.4	39.6	0	0
21	Locked	QAM256	27	591.0	-1.4	39.9	0	0
22	Locked	QAM256	28	597.0	-1.1	40.0	0	0
23	Locked	QAM256	29	603.0	-1.6	39.9	0	0
24	Locked	QAM256	30	609.0	-1.9	39.8	0	0
25	Locked	QAM256	31	615.0	-1.6	39.8	0	0
26	Locked	QAM256	32	621.0	-0.8	40.0	0	0
27	Locked	QAM256	33	627.0	-1.5	39.8	0	0
28	Locked	QAM256	34	633.0	-1.8	39.7	0	0
29	Locked	QAM256	35	639.0	-2.2	39.5	0	0
30	Locked	QAM256	37	651.0	-1.4	39.7	0	0
31	Locked	QAM256	38	657.0	-2.6	39.4	0	0
32	Locked	OFDM PLC	48	657.0	0.0	35.8	89911756	0

 

Great signal to noise ratio (SNR) with no corrected or uncorrected errors except on the OFDM PLC channel, which I believe is to be expected. Amazing!

 

Upstream Bonded Channels

 

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	1	5120	19.3	41.8
2	Locked	SC-QAM	2	5120	25.7	41.0
3	Locked	SC-QAM	3	5120	32.3	40.8
4	Locked	SC-QAM	4	5120	38.7	41.0

 

Speed Test Results (https://speedtest.xfinity.com/results - hardwired)

 

Download speed	900.4 Mbps
Upload Speed	39.5 Mbps
Protocol	IPv6

 

Note: While I didn't get 940 Mbps (real world maximum over gigabit LAN), I wasn't directly wired into my modem. I had other people on the network gaming, playing music, etc, so I am happy with this result all things considered.

 

I wonder if there is any difference between doing the speed test over IPv6 vs IPv4?

 

Summary of how I fixed my problem

 

As both @CCAndrew and @EG said:

I connected the cable inside my house to my modem before it hit any splitters and my problems disappeared.

 

Since I only have cable internet (no cable TV), I don't need splitters. 

 

Thank you both so much!

 

It seems like it was either a bad splitter, poor connections between splitter and connected cables, a bad cable after the splitter or all of the above. Either way, I am happy now to be back to full speeds!

You’re welcome, you may want to still get a tech out sometime. Your downstream “shouldn’t” be in the negatives with no splitters. But definitely looks better

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@CCAndrew wrote:
You’re welcome, you may want to still get a tech out sometime. Your downstream “shouldn’t” be in the negatives with no splitters. But definitely looks better

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Thank you for the advice @CCAndrew. I'll see if I can get a tech out to check things out at some point.

 

To help me learn more, what effect might negative downstream power levels have on my service?

 

Also, should I be worried about upstream power levels less than 42 dBmV? I read on https://www.speedguide.net/faq/what-cable-modem-signal-levels-are-considered-good-78 that ideally upstream power levels want to be above 42 dBmV.

 

Just trying to figure out what SNR and power levels I would see with ideal conditions.

Everything is a range but some numbers (usually in the middle of that range) are ideal. Upstream between 35 and 52, downstream 10 and -10 and SNR above 35 but closer to 39-41 is great. There’s nothing “wrong” with your levels, you’re in the range. There may not be anything wrong it could be a combination of low levels outside, distance from pedestal to the house and then distance to the modem. There is loss of signal over distance