Odd "Signal"

AM signal in a powerpoint? Big brother watching you?

Radio in copper? As to my experience all wires are capable of catching bandwidth of radio signal. Why its only this power point is maybe because of the length of the wire between the connection points.

Others might have a better idea.

Check with am receiver to see if any radio station is near and broadcasting on this frequency...maybe aliens are trying contact you....

Sounds like you have a defective chopper power supply on that circuit. Our maybe a defective vf motor drive? I've seen this caused by bad caps in the primary circuits of high freq power supplies. Don't overlook electronic ballests used in florescent lights. The freq is odd for this but...ya never know! Also, do you have smoke detectors on this circuit? Some of them use power line carrier to trigger simultaneous alarms.....

I agree,

SMPS operate between about 200kHz and 2MHz or more and if their input is not adequately filtered this can appear on the mains.

Since the SMPS is dynamically adjusting the power/current drawn as the load changes it would appear as has been described

Thanks to all, especially Winfield (you always go so in depth!).

In the past, I have found several other SMPS's which generated random artifacts. What struck me as odd about this one was the apparent sidebands I associated with the signal, which may not really be the case. Also, all of the other SMPS artifacts I have come across drift over time, and are affected by temperature and line frequency.

I will be setting up some monitoring equipment to bounce the signal against line freq, but I already have the assumption (since I know my line frequency drifts between 59.9 and 60.1 pretty "reliably") that I will find it is not related to that. I observed the signal over several hours yesterday and it remained steadfast at 591.1 kHz.

I was able to lock onto the peak once I adjusted the internal demod circuit in my spec-an (once I refamiliarized with that function!), and a distinct tone could be discerned. The signal rides about 20 dBv above our noise floor.

I will be checking as many receptacles and panels as I can in order to determine where the best "reception" is. So far, it is limited to one distribution block, so the transformer theory may pan out, we'll see.

We do have a halon system which utilizes a one-detector alarm, two-detector dump so there may be some logic in there which is generating a control tone. That system is fed from a separate distribution circuit, so it's not likely, but an option I will keep open. A supervisory tone was one of the first things that popped into my mind when I found it.

I will keep on with my troubleshooting. Any other ideas are appreciated.

Carrier Current? Many institutions can broadcast that way. It gets them around FCC wattage rating. Broadcast distance is poor about 200 feet. But the whole electrical system is an antenna. So usually reaches the audience intended for.

Not carrier current. We don't want to broadcast anything. Our system is designed to be very quiet. That's why I noticed this and am investigating.

You do not want to broadcast anything, but what if for a small chance you are broadcasting? I stick to the big bro theory for a while until you can explain the thing.

And who would big brother be in this case?

You tell me! There is a lot of Big Bro going on in the world. Who might have an interest in you is maybe hidden from you. Go with Aliens if like you do!

Since I work in a classified facility I would hope that we don't have these types of things going on!

But, that being said, we do tend to run checks and balances so I may have stumbled onto something I shouldn't have (?).

I love conspiracies!

_{^{btw...I am typing this at work so if I am disappeared...}}

Heh, its been a couple of days. Are you still there? Just checking!

:-)

Not carrier current. We don't want to broadcast anything. Our system is designed to be very quiet. That's why I noticed this and am investigating.

I live "off the grid" and make my own electricity via generator. About a year ago a freind was over and we were practicing with an electric guitar and suddenly got AM radio coming from the amplifier. It only lasted a few min. and has not happened since. Your post of an odd signal brought this to mind. I never did figure out what caused it.

Are there more power line specialists out there?

I'm chasing a potential EMI issue in a specific controller I upgraded last year.

I had the fantastic idea to monitor the current in off state to detect failures of the switching device. (hybrid power switch, triac+Relay to protect the relay contacts from arcing)

The current is measured using a small coil.

Typically these coils are not so flat in their frequency response but as the main signal is 50/60Hz, who bothers.

The typical circuit we use contains snubbers, the coil is placed that the current through the snubber in off state is going though it.

Now comes the problem: snubbers are there to absorb the transients but will amplify the higher frequencies above the detection level of no current for the software, invoking alarms.

Strangely this hits us in certain regions in Germany, Switzerland and Scotland. And in waves: the customers call as if they have agreed all the same day for a certain region.

Which measurement should I set up at problem sites?

Are there power analysers capable of looking to the higher harmonics and off harmonics? (above 2kHz)

Are there power analysers capable of taking an external "trigger" so I can catch the minutes before an event in detail? (My scope only takes the last 100 msec if I want detail)

It sound like an AM radio station. Switching power supplies (like in computers) are about a tenth of that frequency in my experience. If it's only one circuit, I would check for an open ground or an open neutral there. Unplug anything you can to see if it goes away.