tpkatl
join:2009-11-16
Dacula, GA | Does signal change when hot weather arrives? Usually my downstream level is right at 0 or -1, and my SNR is around 34-35.
So the changes are not huge, but they tend to be rock solid, and have been for a while - up til last week, when we started getting some serious heat (highs between 99 and 106) in the Atlanta area.
Would heat (and its effect on coax insulation, etc.) be affecting signal? |
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 ropeguruPremium
join:2001-01-25
Mechanicsville, VA | Short answer - Yes |
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 NetFixerFrom my cold dead handsPremium
join:2004-06-24
The Boro
 ·Comcast Business..
 ·Vonage
 ·Cingular Wireless
·Comcast
| reply to tpkatl
As ropeguru said, the short answer is yes.
A more expanded answer is that even if you don't have a problem with expansion/contraction (physics 101) causing physical connection problems, the resistance of copper changes with the temperature (physics 101 again). The resistance changes cause the signal strength to vary (ohm's law 101).
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History does not long entrust the care of freedom to the weak or the timid.
-- Dwight D. Eisenhower |
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 PeteC2Got Mouse?Premium,MVM
join:2002-01-20
Bristol, CT
kudos:6
·Comcast
| reply to tpkatl
Yep, and that is why you do not want your signal to be right at the "edge".
One might well be able to have good connectivity with upstream power levels of 51 - 52, and downstream of -14 dBmV...but variances in temps can skew you past decent connectivity.
The OP's downstream levels are still fine, don't know what the upstream levels are however as they weren't posted.
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Deeds, not words |
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 EGThe wings of lovePremium
join:2006-11-18
Union, NJ
kudos:9 | reply to tpkatl
May I add that the amplifiers / actives that are part of the cable plant / infrastructure have built in AGC (Automatic Gain Control) circuits to help offset these ambient / seasonal temperature variations, and if they are functioning correctly, they will keep the power levels stable to within 3-4 dB at all times. |
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 beachintechThere's sand in my tool bagPremium
join:2008-01-06
kudos:5 | Depending on plant design*. Some areas don't have this to the same degree and have thermal units that attempt the same changes. Don't always work so well.
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Ex-Tech at the Beach.
I speak for myself, not my former employer. |
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 gar187erI do this for a living
join:2006-06-24
Dover, DE
kudos:4 | yup yup...we were one of those until a few agos...we went through and pulled most of them in place of ADUs...
the thermal units cause issues in part cause they take into account the temperature at that amp, and "compensate", well if the amp is baking in the sun, yet the cable is underground, or shaded by trees, its not really doing its job.
The ADUs take into account signal levels, and when the signal raises or lowers the unit turns the amp up or down to keep the levels constant.
beach- i know you know this =)
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I'm better than you! |
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| reply to tpkatl
Higher the temperature, higher the cable attenuaton.
Your downstream signal is about 4 dB lower but your SNR is about 2 dB stronger (this is good) so maybe the input and\or output of a distribution amplifier somewhere on the line was 4 dB too hot and was causing lower SNR!?
The question is, what downstream signal you are supposed to have at your sepcific installation when the cable line is balanced correctly from the node to your tap? We don't know!
Your signals are within specs and if it's not broken, don't fix it. |
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beachintechThere's sand in my tool bagPremium
join:2008-01-06
kudos:5 | reply to gar187er
I do, but thanks for providing more detail  |
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 DarkLogixTexan and ProudPremium
join:2008-10-23
Baytown, TX
kudos:3 | reply to NetFixer
Re: Does signal change when hot weather arrives? said by NetFixer:As ropeguru said, the short answer is yes.
A more expanded answer is that even if you don't have a problem with expansion/contraction (physics 101) causing physical connection problems, the resistance of copper changes with the temperature (physics 101 again). The resistance changes cause the signal strength to vary (ohm's law 101).
And then some devices comcast has may/may not have to setp in and boost/stop boosting the signal |
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