A couple of months ago we began having significant problems with our previously reliable internet. Tech support told me that the signal looked "weak" on their end and so sent a tech. The tech confirmed the signal was bad but thought it was because of a problem with the box (I think he called it a tap) on the pole outside. But because he didn't have time to fix it, he put in an amplifier, called a supervisor, told me the supervisor would call me back, and left. Supervisor never called. Fast forward a week, the problem remains, and I call tech support again. They tell me someone already went to fix the box/tap. But the problem remains, so a second tech comes. The second tech confirms problems with the signal, replaces some connectors outside, including an old one from an old telephony service. The problem gets better for a week or so, but is now back. Packet loss ranges from 0 to as high as nearly 50%. I even got a few "PING: transmit failed. General failure." at one point. In the course of troubleshooting, I check the modem signal levels myself, and see the below. From what I can gather, the power and SNR levels are OK, but the corrected/uncorrectables are extremely high. Googling suggests installing a MoCA filter might help, so I've ordered some. I've also ordered a new cable modem. In the meantime, I figured I'd post the table below to see if anyone has any input. We are in Norfolk, VA. Thanks! Channel Lock Status Modulation Channel ID Frequency Power SNR Corrected Uncorrectables 1 Locked 256QAM 21 903.00 MHz -2.60 dBmV 32.96 dB 3469181 15134936 2 Locked 256QAM 1 783.00 MHz 6.40 dBmV 37.64 dB 148312 832542 3 Locked 256QAM 2 789.00 MHz 6.80 dBmV 38.61 dB 340 3212 4 Locked 256QAM 3 795.00 MHz 6.60 dBmV 37.64 dB 275 2145 5 Locked 256QAM 4 801.00 MHz 7.50 dBmV 38.61 dB 237 2153 6 Locked 256QAM 5 807.00 MHz 7.10 dBmV 38.61 dB 204 2055 7 Locked 256QAM 6 813.00 MHz 6.40 dBmV 37.64 dB 401 3138 8 Locked 256QAM 7 819.00 MHz 6.10 dBmV 37.64 dB 391 2193 9 Locked 256QAM 8 825.00 MHz 5.20 dBmV 37.64 dB 15640 40825 10 Locked 256QAM 9 831.00 MHz 4.30 dBmV 36.61 dB 195030 640385 11 Locked 256QAM 10 837.00 MHz 3.10 dBmV 36.39 dB 81407 461393 12 Locked 256QAM 11 843.00 MHz 2.40 dBmV 35.78 dB 954226 5462733 13 Locked 256QAM 12 849.00 MHz 1.70 dBmV 35.78 dB 9501 2122 14 Locked 256QAM 13 855.00 MHz 0.40 dBmV 34.93 dB 38851 2945 15 Locked 256QAM 14 861.00 MHz 0.10 dBmV 34.48 dB 83281 2831 16 Locked 256QAM 15 867.00 MHz -0.40 dBmV 34.35 dB 121472 3055 17 Locked 256QAM 16 873.00 MHz -0.20 dBmV 34.35 dB 106864 2151 18 Locked 256QAM 17 879.00 MHz -0.40 dBmV 34.35 dB 101284 2164 19 Locked 256QAM 18 885.00 MHz -0.10 dBmV 35.08 dB 63932 2240 20 Locked 256QAM 19 891.00 MHz -0.80 dBmV 34.35 dB 95436 3125 21 Locked 256QAM 20 897.00 MHz -1.60 dBmV 33.49 dB 125114 3167 22 Locked 256QAM 22 909.00 MHz -3.50 dBmV 32.24 dB 13440855 79337484 23 Locked 256QAM 23 915.00 MHz -3.90 dBmV 31.99 dB 15245735 95548338 24 Locked 256QAM 24 921.00 MHz -4.70 dBmV 31.34 dB 15191205 95274441 25 Locked 256QAM 25 927.00 MHz -4.80 dBmV 31.60 dB 5004 65560 26 Locked 256QAM 26 933.00 MHz -5.20 dBmV 31.20 dB 731324 2717 27 Locked 256QAM 27 939.00 MHz -6.50 dBmV 29.70 dB 1770157 2384 28 Locked 256QAM 28 945.00 MHz -7.40 dBmV 29.30 dB 5257792 2836 29 Locked 256QAM 29 951.00 MHz -7.40 dBmV 29.10 dB 7923058 1914 30 Locked 256QAM 30 957.00 MHz -6.90 dBmV 29.50 dB 3769993 3038 31 Locked 256QAM 31 963.00 MHz -7.50 dBmV 29.10 dB 7501271 2645 32 Locked 256QAM 32 969.00 MHz -7.70 dBmV 28.90 dB 22142363 1727 Upstream Bonded Channels Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 1 5120 kSym/s 19.10 MHz 38.00 dBmV 2 Locked ATDMA 6 2560 kSym/s 14.30 MHz 38.50 dBmV 3 Locked ATDMA 4 5120 kSym/s 38.40 MHz 39.50 dBmV 4 Locked ATDMA 3 5120 kSym/s 32.00 MHz 39.00 dBmV 5 Locked ATDMA 2 5120 kSym/s 25.60 MHz 39.00 dBmV

Those signals are still odd. I think the reason you're seeing different numbers is because the modem locked on to a different frequency band. Now you have 400/800 MHz channels instead of 800/900 like you did in your first post. The signals on the 400 MHz channels are too high and there's still a dropoff of almost 10 dBmV between the lowest frequency channel and the highest. Something is affecting the frequency response of the line, and based on the signals I would guess that there is at least one unnecessary amplifier in there along with possibly a high-cut filter or else just a defective cable or other defective part that is negatively affecting higher frequencies.

Cable networks are inherently very fragile. You want everything as perfect as possible. So you want to remove any unnecessary add-ons and get everything you can control in the best possible shape. This isn't a unique problem to Cox. This is a problem for all cable internet networks. It's just a fragile technology. 16.8 dBmV is pretty high in terms of power but I don't think it's high enough to cause damage to the modem. But I would still remove the amp and test. Depending on the problem, removing the amp might cause problems with the 900 MHz channels. First get your indoor stuff as clean as possible then check signals and logs. If you still see issues, call for a tech. Also remember that less is more in the world of cable internet. Avoid any add-ons (amplifiers, attenuators, filters, etc.) unless absolutely necessary. The goal should be to fix it by taking things out, not by putting more things in. Sometimes an add-on is unavoidable but it's always best to try to avoid them.

Major problem with frequency response on that line. An amplifier is definitely not the fix. Your 900 MHz signals are way too low (-20) but 400 MHz are just about perfect (close to 0 which is considered ideal). There should not be that much dropoff in that range of frequencies. Have you replaced all interior cables with brand new high quality RG6 cables? Make sure there is no RG58 or RG59 cabling at all anywhere.

Still the same problem as before. Way too much dropoff between 400 MHz and 900 MHz. Something is attenuating higher frequencies on that line. Could be any of several things. Only thing in your control would be to replace indoor cabling with brand new RG6. And definitely make sure there is no RG58 or RG59.

wptlrn

New Contributor II

4 years ago

Unreliable connection / packet loss / high uncorrectables / multiple tech visits

A couple of months ago we began having significant problems with our previously reliable internet. Tech support told me that the signal looked "weak" on their end and so sent a tech. The tech confirmed the signal was bad but thought it was because of a problem with the box (I think he called it a tap) on the pole outside. But because he didn't have time to fix it, he put in an amplifier, called a supervisor, told me the supervisor would call me back, and left.

Supervisor never called.

Fast forward a week, the problem remains, and I call tech support again. They tell me someone already went to fix the box/tap. But the problem remains, so a second tech comes. The second tech confirms problems with the signal, replaces some connectors outside, including an old one from an old telephony service.

The problem gets better for a week or so, but is now back. Packet loss ranges from 0 to as high as nearly 50%. I even got a few "PING: transmit failed. General failure." at one point.

In the course of troubleshooting, I check the modem signal levels myself, and see the below. From what I can gather, the power and SNR levels are OK, but the corrected/uncorrectables are extremely high. Googling suggests installing a MoCA filter might help, so I've ordered some. I've also ordered a new cable modem.

In the meantime, I figured I'd post the table below to see if anyone has any input. We are in Norfolk, VA.

Thanks!

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Corrected	Uncorrectables
1	Locked	256QAM	21	903.00 MHz	-2.60 dBmV	32.96 dB	3469181	15134936
2	Locked	256QAM	1	783.00 MHz	6.40 dBmV	37.64 dB	148312	832542
3	Locked	256QAM	2	789.00 MHz	6.80 dBmV	38.61 dB	340	3212
4	Locked	256QAM	3	795.00 MHz	6.60 dBmV	37.64 dB	275	2145
5	Locked	256QAM	4	801.00 MHz	7.50 dBmV	38.61 dB	237	2153
6	Locked	256QAM	5	807.00 MHz	7.10 dBmV	38.61 dB	204	2055
7	Locked	256QAM	6	813.00 MHz	6.40 dBmV	37.64 dB	401	3138
8	Locked	256QAM	7	819.00 MHz	6.10 dBmV	37.64 dB	391	2193
9	Locked	256QAM	8	825.00 MHz	5.20 dBmV	37.64 dB	15640	40825
10	Locked	256QAM	9	831.00 MHz	4.30 dBmV	36.61 dB	195030	640385
11	Locked	256QAM	10	837.00 MHz	3.10 dBmV	36.39 dB	81407	461393
12	Locked	256QAM	11	843.00 MHz	2.40 dBmV	35.78 dB	954226	5462733
13	Locked	256QAM	12	849.00 MHz	1.70 dBmV	35.78 dB	9501	2122
14	Locked	256QAM	13	855.00 MHz	0.40 dBmV	34.93 dB	38851	2945
15	Locked	256QAM	14	861.00 MHz	0.10 dBmV	34.48 dB	83281	2831
16	Locked	256QAM	15	867.00 MHz	-0.40 dBmV	34.35 dB	121472	3055
17	Locked	256QAM	16	873.00 MHz	-0.20 dBmV	34.35 dB	106864	2151
18	Locked	256QAM	17	879.00 MHz	-0.40 dBmV	34.35 dB	101284	2164
19	Locked	256QAM	18	885.00 MHz	-0.10 dBmV	35.08 dB	63932	2240
20	Locked	256QAM	19	891.00 MHz	-0.80 dBmV	34.35 dB	95436	3125
21	Locked	256QAM	20	897.00 MHz	-1.60 dBmV	33.49 dB	125114	3167
22	Locked	256QAM	22	909.00 MHz	-3.50 dBmV	32.24 dB	13440855	79337484
23	Locked	256QAM	23	915.00 MHz	-3.90 dBmV	31.99 dB	15245735	95548338
24	Locked	256QAM	24	921.00 MHz	-4.70 dBmV	31.34 dB	15191205	95274441
25	Locked	256QAM	25	927.00 MHz	-4.80 dBmV	31.60 dB	5004	65560
26	Locked	256QAM	26	933.00 MHz	-5.20 dBmV	31.20 dB	731324	2717
27	Locked	256QAM	27	939.00 MHz	-6.50 dBmV	29.70 dB	1770157	2384
28	Locked	256QAM	28	945.00 MHz	-7.40 dBmV	29.30 dB	5257792	2836
29	Locked	256QAM	29	951.00 MHz	-7.40 dBmV	29.10 dB	7923058	1914
30	Locked	256QAM	30	957.00 MHz	-6.90 dBmV	29.50 dB	3769993	3038
31	Locked	256QAM	31	963.00 MHz	-7.50 dBmV	29.10 dB	7501271	2645
32	Locked	256QAM	32	969.00 MHz	-7.70 dBmV	28.90 dB	22142363	1727

Upstream Bonded Channels
Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	1	5120 kSym/s	19.10 MHz	38.00 dBmV
2	Locked	ATDMA	6	2560 kSym/s	14.30 MHz	38.50 dBmV
3	Locked	ATDMA	4	5120 kSym/s	38.40 MHz	39.50 dBmV
4	Locked	ATDMA	3	5120 kSym/s	32.00 MHz	39.00 dBmV
5	Locked	ATDMA	2	5120 kSym/s	25.60 MHz	39.00 dBmV

Dave9

Contributor III

4 years ago

Something is definitely wrong on that line. The SNRs are much lower than they should be and there is a wide variance of power levels with a high of 7.1 dBmV at 807 MHz and a rapid dropoff above 830 MHz to a low of -7.7 dBmV at 969 MHz. That's a range of almost 14 dBmV which is not normal or even close to normal. It's about the worst I've ever seen.

Unfortunately this could be caused by any number of things: faulty parts, faulty cables, etc, etc. Only a Cox tech can diagnose it. You'll need to call for another one, and another, and another until you get one who has the skill and time to resolve the issue. I wouldn't waste time or money on any type of filters or other add-ons until you can get those signals more in line with what they should be.

wptlrn

New Contributor II

4 years ago

Thank you!!

So I actually just plugged in a new modem, have been using it for about 30 minutes, and the connection seems to be better--see below. Could it just be that the modem, which was purchased in 2018, needs to be replaced?

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	37	369.0	16.3	40.3	0	0
2	Locked	QAM256	1	783.0	7.7	36.4	0	0
3	Locked	QAM256	2	789.0	8.6	37.0	0	0
4	Locked	QAM256	3	795.0	8.1	36.7	0	0
5	Locked	QAM256	4	801.0	8.9	37.2	0	0
6	Locked	QAM256	5	807.0	8.8	37.1	0	0
7	Locked	QAM256	6	813.0	7.8	36.4	0	0
8	Locked	QAM256	7	819.0	7.8	36.4	0	0
9	Locked	QAM256	8	825.0	6.8	35.5	0	0
10	Locked	QAM256	33	345.0	16.2	40.1	0	0
11	Locked	QAM256	34	351.0	16.4	40.3	0	0
12	Locked	QAM256	35	357.0	16.7	40.6	0	0
13	Locked	QAM256	36	363.0	16.2	40.3	0	0
14	Locked	QAM256	38	375.0	15.7	40.2	0	0
15	Locked	QAM256	39	381.0	15.4	40.1	0	0
16	Locked	QAM256	40	387.0	14.8	40.0	0	0
17	Locked	QAM256	41	393.0	14.9	41.2	0	0
18	Locked	QAM256	42	399.0	14.5	41.1	0	0
19	Locked	QAM256	43	405.0	14.8	41.0	0	0
20	Locked	QAM256	44	411.0	15.2	41.3	0	0
21	Locked	QAM256	45	417.0	15.8	41.4	0	0
22	Locked	QAM256	46	423.0	16.1	41.6	0	0
23	Locked	QAM256	47	429.0	16.1	41.5	0	0
24	Locked	QAM256	48	435.0	15.3	41.1	0	0
Total							0	0

Dave9
Contributor III
4 years ago
Those signals are still odd. I think the reason you're seeing different numbers is because the modem locked on to a different frequency band. Now you have 400/800 MHz channels instead of 800/900 like you did in your first post. The signals on the 400 MHz channels are too high and there's still a dropoff of almost 10 dBmV between the lowest frequency channel and the highest. Something is affecting the frequency response of the line, and based on the signals I would guess that there is at least one unnecessary amplifier in there along with possibly a high-cut filter or else just a defective cable or other defective part that is negatively affecting higher frequencies.

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