UPS and Cable Modem problems?

[jjohnston]

I have a cable modem from Charter. Haven't had to many problems with it, but last year we were entering the stormy season so after a couple power outages I decided to plug the modem into a UPS. I didn't think anything of it, but over the last year, the modem needs to be power cycled because the internet kept dropping. I had charter out and they ran tests on the modem and said its 100% functional with no errors. Then it hit me, it started around the same time the UPS was hooked up. I plugged the modem into the surge protection only side of the UPS and haven't had an outage yet... its only been 2 weeks, but so far so good.

Do UPS devices cause this? I did try 2 different UPS devices. one was one of the cheaper ones, the other was the "pure sign wave" type. both caused lockups... Just curious if anyone has any knowledge on the use of UPS devices with cable modems.

 

[westom]

Do UPS devices cause this? I did try 2 different UPS devices. one was one of the cheaper ones, the other was the "pure sign wave" type. both caused lockups...

Start by replacing subjective claims with numbers. For example, this 120 volt UPS says pure sine wave. It is 200 volt square waves with a spike of up to 270 volts. From high school math, those square waves and spike are a sum of pure sine waves. So they did not lie. They manipulated the naive who forget a claim without a spec numbers is probably bogus.

Because all electronics are so robust, even that 270 volt spike is acceptable power to electronics.

Now, start with what might be missing so that the UPS would cause problems. Where Charter cable enters the building: does a wire connect cable short to the same earth ground electrode used by AC electric and all other incoming utility wires? If not, a UPS can create stray currents that cause interference and noise.

By lockup, do you mean loss of signal? Modem lights report important and useful facts.

Some modems provide more useful numbers. If you log into the modem's server page, then dB numbers might be available. Review or report all those numbers. Both with a UPS in battery backup mode and when a UPS connects the modem directly to AC mains. dB numbers report far more than any subjective observation.

Unfortunately some modems do not provide those critically important dB numbers. Leaving you to wait for a Charter lineman visit.