Another Strange One

[Jeffrey Lomicka]

In my experience, noise is not what kills X10 signals, what kills 
them is attenuation caused by "RF filtering" in the power supplies of 
modern computer equipment.  This saps the signal strength needed for 
the receivers to pick it up.

So, I suspect the Airport's filtering explains the extra low noise 
numbers, it has filtered out all the noise, as well as most of the 
actual signal.