Compact Fluorescent Noise

["Jeff Volp" <JeffVolp@xxxxxxx>]

While working on the XTB-II AGC loop, I discovered it can be difficult to
deal with nose generated by compact fluorescent bulbs.  A photo of CF noise
in the X10 passband can be found at:

http://jeffvolp.home.att.net/x10xmtbuf/cfnoise.jpg

Zero crossings are at dead center of the trace, and 8.3mS on either side.
As you can see, these CF bulbs generate a burst of noise in the X10/Insteon
passband centered around each zero crossing.  This is exactly when Insteon
and X10 signals are transmitted.

This testing was done in my workshop, which is on a non-X10 circuit powered
through an ArcFault breaker, and has 4 unfiltered CF ceiling lights.  The
pulsating seen in the waveform is due to beating between the noise generated
from the different bulbs.  As the noise pulsates, I measured up to 800mVpp,
which lighted up two solid bars on the ESM1.

The reason this noise is difficult to deal with is that it does pulsate.  So
the point that the AGC samples the noise can be near a null, and the noise
can rise to a peak in the middle of the X10 reception window.  In fact I can
see extra "1"s received when that happens.  It results in a reported
collision, and a rejected message.

While the AGC in the XTB-II works fine for line transients and relatively
constant background noise, it does have a problem with noise that pulsates
in this manner.  I'm not sure there is a way do deal with it, and that is
probably why some CF bulbs cause so many problems.

I thought I would share this info with you.

Jeff