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jimk
Premium
join:2006-04-15
Raleigh, NC
Reviews:
·Time Warner Cable
·voip.ms

[TWC] Digital TV Signal level questions

I have been battling occasional picture pixelation and sound drop-outs on two digital cable boxes lately. When the boxes are having problems, the cable modem will also start to show increased uncorrectable codewords (sometimes building up over a million of these in less than 7 days).

I have been using the diagnostics throughout the day on the cable boxes to try to get to the bottom of this, since the problem never occurs when a tech is here.

I have been informed that whatever the problem is, it is a network issue and not a wiring or equipment issue. The issue has been escalated to maintenance, but so far I have not seen any signs of them doing anything about it after over a week

I have noticed something odd on the cable box diags... the signal varies substantially by channel. Here's what I am seeing now on one of the boxes:

Inband Network-1 (Freq,QAM): 177.000 MHz, Qam256
Inband Quality-1 (PWR,SNR): -1.0 dBmV, 35.0 dB
Inband Errors-1 (Corr/Uncorr): 44 / 0

Inband Network-2 (Freq,QAM): 717.000 MHz, Qam256
Inband Quality-2 (PWR,SNR): 10.0 dBmV, 37.0 dB
Inband Errors-2 (Corr/Uncorr): 0 / 0

On the other box (which has a splitter, so naturally the signal is lower)

Inband Network-1 (Freq,QAM): 177.000 MHz, Qam256
Inband Quality-1 (PWR,SNR): -7.0 dBmV, 35.0 dB

When thepicture and sound problems occur, the Uncorrected errors will start increasing. Sometimes, they seem to reset to zero and start increasing again. Channels running on higher frequencies seem to be impacted more by this issue than the lower frequency channels.

I was wondering if it would ever be normal to see the signals vary this much by channel.

All signals increased by about 2 dBmV after the most recent tech replaced some corroded connections outside. Since this is an apartment, I have no access to the outside wiring. Since I have only 2 outlets and 3 devices, one of them has to be split .

The problems are occasional... they seem to be worst in the mornings or in the evening, but I'm not home that much during the day so it is hard to tell for sure.

Any input would be appreciated. If the large difference in signals between low frequency and high frequency channels indicates a problem, that will be an interesting call with TWC since I'm sure they will question why a customer is looking at the diagnostics.



Jabbu
Premium
join:2002-03-06

Usually it would be the other way, 177 would be received higher at a box then 717, looks like water damage or a suck out fitting somewhere. Problem is maintenance will need to be on site and have it happening while diag. to find the problem.



jimk
Premium
join:2006-04-15
Raleigh, NC
Reviews:
·Time Warner Cable
·voip.ms

said by Jabbu:

Usually it would be the other way, 177 would be received higher at a box then 717, looks like water damage or a suck out fitting somewhere. Problem is maintenance will need to be on site and have it happening while diag. to find the problem.

That's what I was thinking, thanks for verifying this. When dealing with RF, low frequency tends to come in stronger. Additionally, every spec sheet for coax cable clearly shows that there is more attenuation on higher frequency signals.

I have two lines coming in from outside, and both have the same issue, so I'm pretty confident that the most recent tech is correct when he said that the issue isn't inside.


motorola870

join:2008-12-07
Arlington, TX
kudos:3

said by jimk:

said by Jabbu:

Usually it would be the other way, 177 would be received higher at a box then 717, looks like water damage or a suck out fitting somewhere. Problem is maintenance will need to be on site and have it happening while diag. to find the problem.

That's what I was thinking, thanks for verifying this. When dealing with RF, low frequency tends to come in stronger. Additionally, every spec sheet for coax cable clearly shows that there is more attenuation on higher frequency signals.

I have two lines coming in from outside, and both have the same issue, so I'm pretty confident that the most recent tech is correct when he said that the issue isn't inside.

this is usually true but the Aeronautical bands can mess with the SNR though I have a weaker signal on channel 19 (153MHz) than a lot of the upper channels I noticed on my modem around 800MHz or so my signals start to level around 35.5dB on the modem leg but the other legs don't have that problem. On 153MHz my boxes show signals varying from fair to good so yeah I think 19 is used by airplane equipment in my area or emergency networks.