Upstream power levels that are too high will affect a modem connection's consistency. As the levels increase, the modem's ability to connect to the provider decreases, which may cause the modem to power down or disconnect. As with all modulation signals, the upstream power level tends to fluctuate depending on various influences including temperature and signal interference. If the problem is on your end, it may be due to poor cabling, bad connections or a faulty splitter. Troubleshoot your upstream power levels by first capturing the initial results and then begin going through the procedures necessary to identify the problem.
Preliminary Signal Capture
Connect your computer directly to the modem, using an Ethernet cable. Open a Web browser and type your router's IP address in the address bar, such as "192.168.0.1." This accesses the modem's software interface.
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Click the "Status," "Signal" or "Statistics" link. The names can vary by manufacturer and modem model.
Locate the "Upstream" section and find the listed power level. Acceptable levels are usually between 30 dB and 55 dB. If the upstream power is above 55 dB, it needs to be lowered. Disconnect the modem's power, wait five seconds and reconnect it. Check the levels again after it powers up to see if levels have improved.
Checking Line Quality
Locate the first coax jack that enters your home. Figure out how you can connect your modem and computer together from this location, if at all possible. You need to check the signal level from the first entry point to confirm if the signal problem is actually in your home.
Disconnect your cable modem from the coax and power outlet then move it to the first coax jack. Reconnect the coax followed by the power. Test your signal levels again. If the upstream power is still too high at the first jack, there is nothing you can do on your end to resolve the problem. Contact your cable provider and advise them of the levels and steps you have taken to resolve.
Decrease the total number of splitters between your modem's usual location and the service box and check the line for sharp bends or deterioration. If possible, connect a single splitter at the first entry point and run a dedicated line from that splitter to your modem. Use as few splitters as possible for optimal signal quality.
Disconnect each splitter from your line and bring them over to the first outlet in your home. Disconnect the cable modem from the wall outlet and add each of the splitters one at a time between the wall outlet and modem. Go to the modem's software interface and look at the signal levels each time. This will allow you to see if any of your splitters are giving you problems. Replace any bad splitters you find using this process.