mystery signal

Dave Houston · 2005-11-11T16:02:54+00:00

I'm seeing a nearly continuous 2Vpp 120kHz signal on one 'phase'. The other'phase' is clear. There are what resemble triac noise bursts approximately1.6ms 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 berandom half cycles (again in sync with the triac-like bursts, 1.6ms pastZC).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 twoapartments and there are two meters which might be a factor.The signal is not coming from anything in my place but there are 4apartments in the building and 4 more in another building across the streetwhich shares the transformer.A random snapshot of 24 half cycles is 101101101110111110110110 with 1indicating 120kHz presence and 0 its absence. I've been unable to discernany 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 thefirst time I saw the nearly continuous signal. It blocks X-10. It shows upas noise on my ESM1.Any ideas?

Nov 11, 2005 23 Replies

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Dave Houston 20 years ago

Charles,

I don't think that's viable since it might require access to the other apartments and other buildings which might make a schedule hard to arrange. I've got people I can call on if it were critical but there are two 4-unit apartment buildings and one (large) single family residence sharing the utility transformer.

I spoke with the lady downstairs and she can't think of anything new she added. I should be able to catch the other tenants this week.

If I can't track it down it's not a major problem. I've only lost one X-10 controlled device and I can live without it.

It's more the challenge of solving the mystery that interests me. If you look at the scopeshots I published you'll see that it appears to be non-random.

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Marc F Hult 20 years ago

dimmer] circuit designs.

I don't know in what equipment other than dimmers and large UPS's IGBT's are currently being used, but as I wrote before, the list of device that they are being touted for by semiconductor mnufacturers is long:

Washing Machine Air Conditioner HVAC (Compressors, Blowers, Pumps) Refrigerator Small Motor Control Traction Inverter UPS Power Supply Servo Drive Medical Power Supply Motor Drives Inverter Welding

etc

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Lotsa new stuff potentially adding to the powerline cacophony.

HTH ... Marc Marc_F_Hult ww.ECOntrol.org

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Marc F Hult 20 years ago

There's someone living in my house who volunteers to do so. I'm very sure that he even has an ELK X-10 powerline monitor and portable oscilloscope ;-)

... Marc Marc_F_Hult

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Dave Houston 20 years ago

Actually, the Monterey would merely report about 12 BSCs per second. Every half cycle with no 120kHz that is preceded by 3 or more half cycles with

120kHz would be seen as a BSC.

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