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Field note: the internet problem that was really a cable TV booster

An office's internet kept dropping packets after a speed upgrade. The culprit was an old cable TV signal booster sitting in the line. A good reminder to look at the physical path.

A small office had unstable internet: dropped video calls, slow pages, and packet loss that came and went. The modem looked fine. The firewall looked fine. The problem turned out to be a piece of equipment nobody had thought about in years.

What it looked like

  • Internet that worked, but kept stuttering and dropping packets
  • Problems that got worse after the office moved to a faster internet plan
  • Nothing obviously wrong in the firewall or network equipment

What it actually was

When the cable company’s technician traced the line coming into the building, they found the main coax cable ran straight into a cable TV signal booster (an amplifier that strengthens the TV signal for the TVs around the building). The internet modem got its signal from after the booster.

For years that was fine. But faster internet service uses higher frequencies on the cable, and this older booster couldn’t pass them cleanly. The signal reaching the modem was degraded, which showed up as packet loss and instability.

The fix

The technician split the incoming line so it went two ways:

  • One line straight to the modem, with no booster in the way
  • One line to the TV booster, so the televisions still worked

The packet loss disappeared right away, and the connection stabilized.

What I took away from it

  • Check the physical path before blaming the network gear. Follow the cable from where it enters the building to the modem, and look for anything sitting in between: splitters, boosters, old wall plates, or amplifiers left over from years of TV installs.
  • An upgrade can expose an old weak spot. Equipment that worked for years at lower speeds may not handle faster service.
  • Let the provider test the line. Cable technicians have meters that measure signal quality at the modem. It’s worth asking them to test when the problem looks like the connection itself, not your equipment.

For office managers: if your internet got worse after an upgrade, ask the provider to check the line all the way to the modem, and mention any TV equipment in the building. It’s a quick fix when that’s the cause.

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