Equipment: ZOOM TELEPHONICS DOCSIS 3.0 5341-00-00J 343Mbps Cable Modem
Issue: Upload speed consistently under 1 Mbps
Have called "comcast support" several times over the past 48 hrs and still having the same issue, little to no upload speed. Purchased a new cable modem and experienced the same performace. Bypassed all equipment (router and splitter) but same results.
Current hookup - new coax cable going directly into the cable modem. Ethernet cable going to laptop.
Speed test results:
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The upstream power is too high and may be intermittently fluctuating even higher out of spec. That can cause random disconnects, spontaneous re-booting of the modem, and speed and latency problems.
In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test
If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.