High Post RS Errors

Looks like there is still an issue with my connection.

This began after upgrading my 250 Mbps to 500 Mbps. Download speeds were dropping to under 100 Mbps, with many log errors. Engineer visited and installed what I believe is a booster and he also replaced the Hub 3 with a Hub 5.

The engineer visit seemed to have done the trick in terms of full download speeds being restored,  however, I decided to keep an eye on the router logs out of curiosity.

As you can see below, channel 2 in particular shows a significant Post RS Error count and has been doing so daily, apart from a 24 hour period where they did not change at all.

3.0 Downstream channels

Channel    Frequency (Hz)    Power (dBmV)    SNR (dB)    Modulation    Channel ID
1    331000000    7.2    41    QAM 256    25
2    139000000    9.4    41    QAM 256    1
3    155000000    10.2    41    QAM 256    3
4    163000000    9.6    41    QAM 256    4
5    171000000    9.6    41    QAM 256    5
6    179000000    9.3    41    QAM 256    6
7    187000000    9.1    41    QAM 256    7
8    195000000    9.2    41    QAM 256    8
9    203000000    8.8    41    QAM 256    9
10    211000000    9    41    QAM 256    10
11    219000000    8.8    41    QAM 256    11
12    227000000    8.3    41    QAM 256    12
13    235000000    8.4    41    QAM 256    13
14    243000000    8.3    41    QAM 256    14
15    251000000    7.9    41    QAM 256    15
16    259000000    7.4    41    QAM 256    16
17    267000000    7.4    41    QAM 256    17
18    275000000    7.5    41    QAM 256    18
19    283000000    7.5    41    QAM 256    19
20    291000000    7.8    41    QAM 256    20
21    299000000    7.7    41    QAM 256    21
22    307000000    7.5    41    QAM 256    22
23    315000000    7.5    41    QAM 256    23
24    323000000    7.3    41    QAM 256    24
25    339000000    7    41    QAM 256    26
26    347000000    7.3    41    QAM 256    27
27    355000000    7.4    41    QAM 256    28
28    363000000    7.1    41    QAM 256    29
29    371000000    7.1    41    QAM 256    30
30    379000000    7.1    41    QAM 256    31
31    387000000    6.9    41    QAM 256    32

3.0 Downstream channels

Channel    Locked Status    RxMER (dB)    Pre RS Errors    Post RS Errors
1    Locked    41    157233    37
2    Locked    41    26731573    607146
3    Locked    41    18054991    281359
4    Locked    41    15302601    202199
5    Locked    41    12881224    142652
6    Locked    41    10599240    95668
7    Locked    41    8354126    56744
8    Locked    41    6734632    34929
9    Locked    41    5426357    20430
10    Locked    41    4425721    12282
11    Locked    41    3318466    6097
12    Locked    41    2549783    3135
13    Locked    41    2019041    1855
14    Locked    41    1692876    1299
15    Locked    41    1510718    1032
16    Locked    41    1216143    638
17    Locked    41    990165    465
18    Locked    41    828070    312
19    Locked    41    681410    213
20    Locked    41    499564    164
21    Locked    41    383482    119
22    Locked    41    314669    77
23    Locked    41    248612    34
24    Locked    41    202205    35
25    Locked    41    125396    23
26    Locked    41    93742    18
27    Locked    41    73544    22
28    Locked    41    61379    21
29    Locked    41    51272    16
30    Locked    41    38521    16
31    Locked    41    25616    16

There are no T1, T2 or T4 errors, but there is a single T3 error.

3.0 Upstream channels

Channel    Frequency (Hz)    Power (dBmV)    Symbol Rate (ksps)    Modulation    Channel ID
0    49600000    46    5120    QAM 64    1
1    43100000    45.8    5120    QAM 64    2
2    36600000    46.3    5120    QAM 64    3
3    30100000    46.5    5120    QAM 64    4
4    23600000    45.5    5120    QAM 64    5

My download speeds are normal at the moment, but the Post RS Errors count is increasing daily. There are also Event 24 and Event 16 messages appearing in the log.

I ask ChatGPT to interpret the logs:

I am seeing ongoing downstream errors on my Hub 5. My speeds and latency are fine, and upstream power levels and T1–T4 timeouts are all normal, but the downstream error levels are much higher than they should be.

Most of the Post-RS errors are concentrated on the lower DOCSIS 3.0 channels, especially around 139–200 MHz. The DOCSIS 3.1 OFDM channel is also showing a large number of corrected errors and some uncorrectables.

Downstream power and SNR readings are all within expected ranges, so this looks like downstream-only ingress or noise rather than a general signal issue.

The most likely causes are:

- A problem with the tap port in the street cabinet, such as corrosion or a poor connection.

- A damaged or degraded drop cable running to the property.

- Loose or corroded F-connectors or the isolator inside or outside the house.

- Noise entering the network from another customer on the same tap.

Recommended fix:

I would appreciate an engineer checking the tap port in the cabinet, the drop cable to the house, and all F-connectors and the isolator. It may also be worth checking for noise affecting the downstream frequencies around 139–200 MHz, as this is where the majority of the errors are occurring.

Mods, I'd rather not explain this to an agent, so can you please arrange for this to be looked into.

Cheers