Monthly Archives: August 2008

Blinky Lights

It should be the goal of every good geek to build something with lots of blinking lights. I’m proud to say that I’ve done this many times over. The latest…

Too bad the system this set of drive arrays is attached to is causing me no end of grief.

Ten Times

I’m really tired of needing to apologize to Comcast. They’re evil. I know this. But I’m really getting annoyed with having what I perceive to be their problems actually be problems on my end.

I’ve been having a lot of problems with random cable modem disconnects due to lack of signal over the past few weeks. I know this because I’m a dork and wrote a script that plugs into my Cacti installation and logs the signal levels displayed in my cable modem’s admin interface. I did this years ago because – you guessed it – Comcast is evil and their stuff cut out on me enough for me to want to be able to monitor it. There has been a steady and constant trend of ever-dropping signal levels that has made itself apparent since the beginning of the year. I’ve had the same general layout in the apartment in terms of devices and number signal paths, so I could only assume that the problem was upstream on Comcast’s side. I was so confident that this was yet another Comcast screw-up that I ordered DSL.

Well, it wasn’t.

I had a service appointment scheduled with Comcast on Friday. The guy did some tests outside where my line plugs in, and he said he noticed a lot of signal “reflection”, and said that my splitters and/or wiring were probably bad. He looked around, and also noticed that I was running my cable through the Monster way-too-much-money power strip, and called that a no-no as well. He replaced three splitters with two nicer ones, and ran custom length cables to each one of my devices. The result?

[signal graph]

As you can see, the signal levels improved dramatically. The downstream power, which is what I receive from Comcast, is up by at least 10dBmV (depending on the time of day). 10dB corresponds to a ten-fold signal power increase. Signal-to-noise ratio is also better than it was, but not by as striking of an amount.

What’s are the lessons here? Use good splitters. Use good cable. Don’t assume Comcast is at fault because they’re evil.

EDIT: My dad has corrected me. The 10dB increase probably only corresponds to around a 3.1 fold increase in power. I think I read the wikipedia chart wrong.