Upstream power too high?

Question

I've been having connection drop-out issues for the past few months (~180 reconnects within the last month according to VM, though I only saw a drop 1-2 a day for 5-90 mins at a time). I'd been mostly away from home so didn't bother about it until this week, when VM sent out an engineer to investigate (10th July).

The engineer removed an old NTL attenuator/splitter, along with the splitter for the broadband and TV (as I plan to ditch the TV). He also switched out my Hub 3 for a Hub 5, which has an inline attenuator on its cable feed.

Annoyingly I didn't note the full line stats before the changes, but the engineer said the downstream was reporting as -8 dBmV, and after these changes is now 0 to -5 dBmV with an SNR of 40 dB.

I'm still having drop-outs (and T2 and T3 timeouts), though less frequent (1 time a day for 1-5 mins at a time), and from doing some research I suspect my upstream power is still too high. It's currently sitting at 52 dBmV, but I've seen it get as high as 59 dBmV immediately after the modem reconnected (it drops back down to 52 dBmV over a span of ~20 mins once the connection is back up).

I just wanted to confirm my understanding is correct before requesting another engineer visit to correct the upstream power.

I tried to add the full line stats and log into this post, but the forums report "Your post contains invalid HTML." if I do... that used to work.

Anonymous · Answer

Firstly ”...180 reconnects within the last month according to VM”; yeah firstly ignore that, they have just made that figure up, means nothing.

Now yes, your logs are a complete mess, so yes not surprised that your upstream power is at that level and also, really you only have one locked upstream channel?

The way that it works is this, the hub increases the upstream power in an attempt to communicate with the CMTS (that’s the device which is ultimately at the other end of the cable). It keeps ramping up the power until either it gets a stable connection or it hits its upper limits (which oddly enough is 59 dBmV, after which it reboots).

High upstream power is not a problem it itself which needs to be fixed, it's an indication that something else is wrong. Mostly likely a bad cable connection between your hub and the street cabinet, possibly also a faulty amp in said cabinet or an upstream cabinet.

“....but the engineer said the downstream was reporting as -8 dBmV, and after these changes is now 0 to -5 dBmV with an SNR of 40 dB."

Great, good, but irrelevant, you have a cable issue which is allowing noise ingress and killing your upstream connection. Sorry but, good luck getting VM to either understand or deal with it.

spudandbeanz · Answer

Apologies for the formatting below. It would only let me post it when pasted as plain text.3.0 Downstream channelsChannel &nbsp; &nbsp;Frequency (Hz) &nbsp; &nbsp;Power (dBmV) &nbsp; &nbsp;SNR (dB) &nbsp; &nbsp;Modulation &nbsp; &nbsp;Channel ID1 &nbsp; &nbsp;306000000 &nbsp; &nbsp;-3.3 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;222 &nbsp; &nbsp;138000000 &nbsp; &nbsp;0.8 &nbsp; &nbsp;41 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;13 &nbsp; &nbsp;146000000 &nbsp; &nbsp;0.4 &nbsp; &nbsp;41 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;24 &nbsp; &nbsp;154000000 &nbsp; &nbsp;0.1 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;35 &nbsp; &nbsp;162000000 &nbsp; &nbsp;0.3 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;46 &nbsp; &nbsp;170000000 &nbsp; &nbsp;0.5 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;57 &nbsp; &nbsp;178000000 &nbsp; &nbsp;0.7 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;68 &nbsp; &nbsp;186000000 &nbsp; &nbsp;-1.1 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;79 &nbsp; &nbsp;194000000 &nbsp; &nbsp;-1.2 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;810 &nbsp; &nbsp;202000000 &nbsp; &nbsp;-1.3 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;911 &nbsp; &nbsp;210000000 &nbsp; &nbsp;-1.3 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1012 &nbsp; &nbsp;218000000 &nbsp; &nbsp;-1.6 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1113 &nbsp; &nbsp;226000000 &nbsp; &nbsp;-1.8 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1214 &nbsp; &nbsp;234000000 &nbsp; &nbsp;-2.2 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1315 &nbsp; &nbsp;242000000 &nbsp; &nbsp;-2 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1416 &nbsp; &nbsp;250000000 &nbsp; &nbsp;-2 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1517 &nbsp; &nbsp;258000000 &nbsp; &nbsp;-2.3 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1618 &nbsp; &nbsp;266000000 &nbsp; &nbsp;-2.5 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1719 &nbsp; &nbsp;274000000 &nbsp; &nbsp;-2.7 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1820 &nbsp; &nbsp;282000000 &nbsp; &nbsp;-2.5 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;1921 &nbsp; &nbsp;290000000 &nbsp; &nbsp;-2.5 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2022 &nbsp; &nbsp;298000000 &nbsp; &nbsp;-2.7 &nbsp; &nbsp;40 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2123 &nbsp; &nbsp;314000000 &nbsp; &nbsp;-3.4 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2324 &nbsp; &nbsp;322000000 &nbsp; &nbsp;-3.8 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2425 &nbsp; &nbsp;330000000 &nbsp; &nbsp;-4 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2526 &nbsp; &nbsp;338000000 &nbsp; &nbsp;-4 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2627 &nbsp; &nbsp;346000000 &nbsp; &nbsp;-4.4 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2728 &nbsp; &nbsp;354000000 &nbsp; &nbsp;-4.4 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2829 &nbsp; &nbsp;362000000 &nbsp; &nbsp;-4.3 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;2930 &nbsp; &nbsp;370000000 &nbsp; &nbsp;-4.3 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;3031 &nbsp; &nbsp;378000000 &nbsp; &nbsp;-4.5 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;3132 &nbsp; &nbsp;386000000 &nbsp; &nbsp;-4.7 &nbsp; &nbsp;39 &nbsp; &nbsp;QAM 256 &nbsp; &nbsp;323.0 Downstream channelsChannel &nbsp; &nbsp;Locked Status &nbsp; &nbsp;RxMER (dB) &nbsp; &nbsp;Pre RS Errors &nbsp; &nbsp;Post RS Errors1 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;71 &nbsp; &nbsp;02 &nbsp; &nbsp;Locked &nbsp; &nbsp;41 &nbsp; &nbsp;46 &nbsp; &nbsp;03 &nbsp; &nbsp;Locked &nbsp; &nbsp;41 &nbsp; &nbsp;60 &nbsp; &nbsp;54 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;60 &nbsp; &nbsp;05 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;65 &nbsp; &nbsp;06 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;59 &nbsp; &nbsp;07 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;45 &nbsp; &nbsp;08 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;63 &nbsp; &nbsp;09 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;37 &nbsp; &nbsp;010 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;55 &nbsp; &nbsp;011 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;46 &nbsp; &nbsp;012 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;56 &nbsp; &nbsp;013 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;58 &nbsp; &nbsp;014 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;62 &nbsp; &nbsp;015 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;64 &nbsp; &nbsp;016 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;57 &nbsp; &nbsp;017 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;64 &nbsp; &nbsp;018 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;59 &nbsp; &nbsp;019 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;58 &nbsp; &nbsp;020 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;55 &nbsp; &nbsp;021 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;71 &nbsp; &nbsp;022 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;76 &nbsp; &nbsp;023 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;77 &nbsp; &nbsp;024 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;67 &nbsp; &nbsp;025 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;59 &nbsp; &nbsp;026 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;72 &nbsp; &nbsp;027 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;68 &nbsp; &nbsp;028 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;73 &nbsp; &nbsp;029 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;89 &nbsp; &nbsp;030 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;78 &nbsp; &nbsp;031 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;77 &nbsp; &nbsp;032 &nbsp; &nbsp;Locked &nbsp; &nbsp;39 &nbsp; &nbsp;74 &nbsp; &nbsp;03.1 Downstream channelsChannel &nbsp; &nbsp;Channel Width (MHz) &nbsp; &nbsp;FFT Type &nbsp; &nbsp;Number of Active Subcarriers &nbsp; &nbsp;Modulation (Active Profile) &nbsp; &nbsp;First Active Subcarrier (Hz)159 &nbsp; &nbsp;92 &nbsp; &nbsp;4K &nbsp; &nbsp;1800 &nbsp; &nbsp;QAM 4096 &nbsp; &nbsp;11283.1 Downstream channelsChannel ID &nbsp; &nbsp;Locked Status &nbsp; &nbsp;RxMER Data (dB) &nbsp; &nbsp;PLC Power (dBmV) &nbsp; &nbsp;Corrected errors (Active Profile) &nbsp; &nbsp;Uncorrectable errors (Active Profile)159 &nbsp; &nbsp;Locked &nbsp; &nbsp;40 &nbsp; &nbsp;-4.7 &nbsp; &nbsp;3934885581 &nbsp; &nbsp;03.0 Upstream channelsChannel &nbsp; &nbsp;Frequency (Hz) &nbsp; &nbsp;Power (dBmV) &nbsp; &nbsp;Symbol Rate (ksps) &nbsp; &nbsp;Modulation &nbsp; &nbsp;Channel ID0 &nbsp; &nbsp;36600000 &nbsp; &nbsp;51.8 &nbsp; &nbsp;5120 &nbsp; &nbsp;QAM 64 &nbsp; &nbsp;113.0 Upstream channelsChannel &nbsp; &nbsp;Channel Type &nbsp; &nbsp;T1 Timeouts &nbsp; &nbsp;T2 Timeouts &nbsp; &nbsp;T3 Timeouts &nbsp; &nbsp;T4 Timeouts0 &nbsp; &nbsp;ATDMA &nbsp; &nbsp;0 &nbsp; &nbsp;4 &nbsp; &nbsp;0 &nbsp; &nbsp;0Network LogTime &nbsp; &nbsp;Priority &nbsp; &nbsp;Description13-07-2025 12:44:18 &nbsp; &nbsp;warning &nbsp; &nbsp;DBC-REQ Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=****;CMTS-MAC=****;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:44:17 &nbsp; &nbsp;critical &nbsp; &nbsp;SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:33:15 &nbsp; &nbsp;notice &nbsp; &nbsp;REGISTRATION COMPLETE - Waiting for Operational status13-07-2025 12:33:10 &nbsp; &nbsp;warning &nbsp; &nbsp;REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:33:04 &nbsp; &nbsp;notice &nbsp; &nbsp;DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:33:03 &nbsp; &nbsp;notice &nbsp; &nbsp;TLV-11 - unrecognized OID;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:55 &nbsp; &nbsp;warning &nbsp; &nbsp;DHCP WARNING - Non-critical field invalid in response ;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:53 &nbsp; &nbsp;notice &nbsp; &nbsp;Honoring MDD; IP provisioning mode = IPv413-07-2025 12:32:40 &nbsp; &nbsp;warning &nbsp; &nbsp;ToD request sent - No Response received;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:40 &nbsp; &nbsp;critical &nbsp; &nbsp;No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:30 &nbsp; &nbsp;warning &nbsp; &nbsp;REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:25 &nbsp; &nbsp;notice &nbsp; &nbsp;DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:23 &nbsp; &nbsp;notice &nbsp; &nbsp;TLV-11 - unrecognized OID;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:16 &nbsp; &nbsp;warning &nbsp; &nbsp;DHCP WARNING - Non-critical field invalid in response ;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:32:14 &nbsp; &nbsp;notice &nbsp; &nbsp;Honoring MDD; IP provisioning mode = IPv413-07-2025 12:32:02 &nbsp; &nbsp;critical &nbsp; &nbsp;Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;13-07-2025 12:31:35 &nbsp; &nbsp;warning &nbsp; &nbsp;ToD request sent - No Response received;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:59:03 &nbsp; &nbsp;warning &nbsp; &nbsp;DBC-REQ Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:59:03 &nbsp; &nbsp;critical &nbsp; &nbsp;SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:48:20 &nbsp; &nbsp;critical &nbsp; &nbsp;Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:48:00 &nbsp; &nbsp;notice &nbsp; &nbsp;REGISTRATION COMPLETE - Waiting for Operational status12-07-2025 09:47:54 &nbsp; &nbsp;warning &nbsp; &nbsp;REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:47:48 &nbsp; &nbsp;notice &nbsp; &nbsp;DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:47:47 &nbsp; &nbsp;notice &nbsp; &nbsp;TLV-11 - unrecognized OID;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:47:38 &nbsp; &nbsp;warning &nbsp; &nbsp;DHCP WARNING - Non-critical field invalid in response ;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:47:36 &nbsp; &nbsp;notice &nbsp; &nbsp;Honoring MDD; IP provisioning mode = IPv412-07-2025 09:46:59 &nbsp; &nbsp;critical &nbsp; &nbsp;Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:46:56 &nbsp; &nbsp;critical &nbsp; &nbsp;Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:46:10 &nbsp; &nbsp;critical &nbsp; &nbsp;Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=****;CMTS-MAC=****:cd;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:45:39 &nbsp; &nbsp;critical &nbsp; &nbsp;SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=****;CMTS-MAC=****;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:45:38 &nbsp; &nbsp;warning &nbsp; &nbsp;Lost MDD Timeout;CM-MAC=****;CMTS-MAC=****;CM-QOS=1.1;CM-VER=3.1;12-07-2025 09:45:27 &nbsp; &nbsp;critical &nbsp; &nbsp;SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=****;CMTS-MAC=****;CM-QOS=1.1;CM-VER=3.1;

Cardiffman282 · Answer

The upstream power level is too high but more importantly you only seem to have one upstream channel. Is that correct?&nbsp;Also check for local faults on 0800 561 0061.&nbsp;

legacy1 · Answer

The attenuator was likely need when the amp was working correctly removing a attenuator don't not fix this.

spudandbeanz · Answer

One channel is indeed what the router shows. This is a M125 connection FWIW.

The online fault checker has just been switching between "There is intermittent signal in your area" and "We need to send an engineer" for the past few months, though now it says "No broadband issues found".

Given this connection had been stable for years, and given nothing changed on my side, I do suspect I got moved to a different tap or something a few months back.

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Upstream power too high?

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