Flaky Wireless Router

I purchased a new Airport Extreme wireless router the other day, and also a new networked HD tuner. I installed both at the same time which is something I usually never do to avoid ambiguity when something breaks. I noticed some flaky internet performance so thinking it was the new Airport Extreme (which gets very good review), I made changes to a bunch of settings. The performance problem was also very hard to notice because it was random flakiness. The most noticeable problem was with live video including Skype and my girlfriend's live video feed for the class she was taking.

Long story short, it turned out to be the cable modem. Why? I inserted an extra 1 to 3 coax splitter before the cable modem.

Prior to this problem I never payed any attention to the signal strength readouts on my cable modem's web page. My Motorola surfboard modem serves up a page at 192.168.1.100 on my network. Following are some snapshots from the web page with different coax splitter configurations in between the coax line entering our house and our cable modem.

1:5 coax splitter at the house + 1:3 before cable modem:


1:5 coax splitter at the house:


1:2 coax splitter at the house:


An explanation of these numbers can be found here. As you can see, with the 1:5 and 1:3 splitter my downstream power level was at -16dBmV which is out of the recommended range. With just a 1:2 splitter, the downstream power level increased to 0dBmV, SNR has increased, and our flaky internet problems are gone.

I'm still trying to make sense of the upstream power level and why it should be *lower*. My current theory is the cable company sends commands to the cable modem to increase its output power if the cable company can't hear the modem? If that was the case, then seeing a lower upstream power level would mean the upstream signal is clear with lower upstream power.