Re: mystery signal

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:4374b9f2.38688863@xxxxxxxxxxxxxxxx
> I'm seeing a nearly continuous 2Vpp 120kHz signal on one 'phase'. The
other
> 'phase' is clear. There are what resemble triac noise bursts approximately
> 1.6ms after each zero crossing and the 120kHz seems to be in sync with
them.
>
> I say nearly continuous because the signal is absent on what appear to be
> random half cycles (again in sync with the triac-like bursts, 1.6ms past
> ZC).
>
> I say 'phase' because while the two circuits seem to have no
communication,
> they are in phase when observed on a scope. My apartment was originally
two
> apartments and there are two meters which might be a factor.
>
> The signal is not coming from anything in my place but there are 4
> apartments in the building and 4 more in another building across the
street
> which shares the transformer.
>
> A random snapshot of 24 half cycles is 101101101110111110110110 with 1
> indicating 120kHz presence and 0 its absence. I've been unable to discern
> any clear pattern other than the OFFs never last beyond a single half
cycle.
>
> The triac noise pulses have been here for a few years but yesterday was
the
> first time I saw the nearly continuous signal. It blocks X-10. It shows up
> as noise on my ESM1.
>
> Any ideas?

Can you determine whether the signal gets stronger as you get closer to the
breaker panel?  It's probably an external signal, but it would be nice to
know for sure.

Don't baby monitors and intercoms that work via powerlines put out similar
interference?  I would assume that an apartment is much more likely to have
"neighbor issues" then single family homes just because units are closer
together.  Are there any hallway outlets that you could check to get a
signal level?  You might be able to triangulate in on the source that way.
Will your neighbors let you poke around their places with an ESM1?

This brings up an interesting question.  How can an apartment dweller block
such signals (assuming they are external) easily without inducing the
landlord to modify the breaker panel?

Have you checked to see if any of your experimental setups are still on
line?  Is it possible that some piece of X-10 gear has gone wild and is just
sending out random pulses?

--
Bobby G.