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Upstream power level increases in hot weather

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Anonymous (not verified)
Upstream power level increases in hot weather

Hi, my first post here :D

I have a problem and maybe someone could help. Since i became a cable broadband subscriber, 5 months ago, I've had many problems with drop connections due to high upstream levels mainly during the day when temp outside increases, at night and on cloudy days the upstream power level stabilizes at 48 to 50 dBmV, around 11 am it starts to increase to 52 and at times jumps to 61 dBmV, the modems max power, most afternoons it stays at 61 until around 7 pm with several drop connections in between. Unbelievably the cable company hasn't been able to solve the problem but last week they finally came to the conclusion that the problem is not in my house but outside... :roll:

Does anyone have any idea what cable equipment outside could be affected so much by certain temperatures? The cable to the pole is 1 year old and the tv picture quality is always good on any channel but during those power level jumps there is a brief static like interference in the picture.

Any ideas would be appreciated. Thanks

P.S I live in Portugal 8)

Upstream power level increases in hot weather

Your cable operator will likely find a bad cable, connector, splitter or tap. It may not necessarily be on your property. 3dB of thermal swing every day is normal as thermal conductivity properties change and the coax contracts and expands with the heat. More than that indicates that something is faulty or not connected properly. The proper transmit levels for the modem shouldn't go much beyond 50dB. You should call for service when the transmit levels are at +61 -- that should tip off the cable company that there's a problem. Tell the technician that arrives at your home that the levels go up and down each day just in case he wasn't informed.

The "sweet spot" for levels are in this range:
-10dB to +4dB receive
+41 to +49 transmit

p.s. These forums are generally for cable plant operators and cover discussion of provisioning and cable modem termination systems. You're always welcome, but you'll probably find that sites like has better resources for end users -- modem and cable company reviews, windows tips, tweaks for VoIP and gaming, etc. Good luck!

Anonymous (not verified)
Upstream power level increases in hot weather

Thanks for the help, problem seems to be resolved, technicians at the head office did some tweaking and the modem has stayed online without any drops for the past 7 days, something that hasn't happened since day one (5 months)

Heres my signal levels now, the 48 dB rises a couple of dB's around 3pm during peak temperatures outside.

Power 2 dBmV
Signal to Noise Ratio 33 dB Modulation QAM64

Power 48 dBmV
Upstream Data Rate 2560 Ksym/sec Modulation QPSK

Interesting forum, keep up the good work :wink:

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