Re: Compact Fluorescent Noise

["Jeff Volp" <JeffVolp@xxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:4548fee6.266423859@xxxxxxxxxxxxxxxx
> "Jeff Volp" <JeffVolp@xxxxxxx> wrote:
>
> >One other thing I noted while looking at the scope photos is that timing
of
> >X10 bursts at other than the zero crossing is not well defined.  Please
look
> >at the following two photos:
> >
> >http://jeffvolp.home.att.net/x10xmtbuf/linenoise1.jpg
> >
> >http://jeffvolp.home.att.net/x10xmtbuf/linenoise.2jpg (fixed)
> >
> >Notice how the X10 bursts move from one sample to the next.  Also note
the
> >zero crossing burst is fixed as is the line transient just after the
center
> >zero crossing.  That third burst moves just about 1mS, and I don't see
how
> >it could hit the reception window in a three-phase system.  Signals were
> >transmitted from a RR501 in response to a palmpad.
>
> I've never seen that and I've looked at a lot of scope traces from various
> X-10 devices. In fact, I've always been rather impressed that the 120kHz
is
> really 120kHz and other timings are near right on using 30 year old LC
> technology. For some examples, take a look at the screenshots in this
> link...
>
>      http://davehouston.net/x10-sig.htm
>
> My pseudo-scope measures frequency and amplitude of a signal, making some
> measurements fairly easy.
>
> I suspect either that you have an erratic RR501 or there's something amiss
> in your setup or that your scope has rheumatism.
>
> It sounds like a neigbor has an intercom or baby monitor.

That 120KHz is everywhere - even pick it up with the scope probe floating.
Sometimes the modulation looks like music.  While I had seen it
intermittently in the past, it has been on all day today.

Looking further into the wandering pulses, it seems to be data related.  I
had thought it might be due to the RR501 power supply sagging, but that is
not the case.  Dim commands are stable where they should be.  F-ON or OFF
commands from the Palmpad causes misalignment of the bursts, usually in the
"ON" or "OFF" portion.  The center burst moves about .5 mS, and the third
burst jumps 1mS.  It doesn't slew, it jumps.  It is not an erratic RR501
because both Powerhouse and Leviton versions purchased years apart exhibit
the same characteristic.  It is not scope triggering because the zero
crossing burst is always where it should be, and the background line
glitches also remain stable in the trace.

Jeff