Cable modem and wiring checklist

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For connection issues here are some simple things to check and/or do:

  1. All unused coax cables disconnected. No dead/unused/open/unterminated coaxes anywhere.
  2. No tight bends in coax (3 inch min bend radius).  If cable has been bent tighter it is likely damaged and needs to be replaced.
  3. No cable damage due to squirrels, etc.
  4. Check for corroded or oxidized coax connectors, especially connectors exposed to outdoor or humid conditions . Unscrew each F-connector and inspect center conductor for oxidation.  The center wire should be shiny copper and extend 1/8" beyond the nuts. Clean center conductor and other parts of connector. If not possible to clean, replace F-connector. Re-attach and tighten just beyond finger tight. (7/16 inch wrench)
  5. Tighten all connections just beyond finger tight.
  6. All unused ports terminated. (check Set-top Box (STB) or tuner for a feed through or daisy chain. Terminate on last box’s port.)
  7. Do not route coax through any other devices en route to modem from Spectrum box on side of house/building. An example of other devices would be a surge protector with coax connectors.
  8. Modem cable input:
  1. The modem is either directly attached to the outside coax or to the first 2 way first splitter; port marked “-3.5 db”. If splitter is n-way splitter, n>2, then use port marked “-3.5 db”. if no such port exists then splitter is not appropriate to use for modem.
  2. Use of unity gain, 0 db, amplifiers is OK if amplifier has “Active Return”, i.e., it amplifies downstream as well as upstream signals, usually gain in both directions is “0 db”. Some of these amps have a VoIP port for use with phones. This VoIP is actually a passive 2 way splitter inside the amp case that precedes the internal amplifier. It is not powered and so will deliver signal to telephone/VoIP port in case of power loss. This port is usually marked as “-3.5 db”.
  1. Use “home run” wiring. This means that all devices are on their own coax that runs to a one common point in house. This common point is where the amplifier or splitter would reside. No other splitters or amps exist anywhere else in house.
  2. Temporary test configuration: disconnect the other coax cables at the first splitter and terminate any unused ports, leaving just the modem on the Spectrum connection. If problem occurs this will help rule out the other equipment on the network.
  3. If modem is a combo type, includes router/WiFi, then disable router and WiFi functions, also known as “bridge” mode. Connect separate router or pc directly to modem’s ethernet port.
  4. Used wired ethernet connections for all testing. WiFi debug is a separate diagnostic exercise.
redrock in Austin, Tx
Spectrum Employee

Re: Cable modem and wiring checklist

[ Edited ]

Great information, a very in depth look at troubleshooting your connection.