Strange AM radio signal in my home. - Page 1
Forum section: electronics / general

author: Ampera
author_rank: Super Contributor
timestamp: July 26, 2019, 03:50:11 am
content: This is likely nothing, but I had tuned an AM radio within a room of my house, and at around 570khz, I found a strange non-repeating signal.It is currently nighttime, however, it is incredibly localized. I have never noticed this before, so I cannot say how long this signal might have been present, but here's the strange part. The epicenter of this transmission appears to be in a T of wall (where two corners meet).The following electronics that are powered and I am aware of are in this range: GFCI outlets, flat US light switch with embedded orange (flickery) light, possibly some mains wiring, and not much above or below the radio besides a bench freezer, a gas water heater, and hot water pump.The sound was recorded (using a microphone, there is background noise, but nothing besides an air conditioner) and I have put it here:http://amperaa.net/cdn/strangenoise.mp3This signal alters speed and tone to no particular pattern, has no considerable breaks, and does not seem to be any particular code. It has a transmission radius of around 1.5m, which very sharply drops off. As for the sources, the light switch with the light will not alter even if the light is on or off (the switch's little bulb, or whatever it uses, I've forgotten what they're called), and the hot water heater/pump does not alter the signal when powered on or off, as far as I can tell.I know this could be literally anything, but it's gotten me stupidly curious, so I'd be curious if anyone could give an idea as to what this might be.

author: Dundarave
author_rank: Regular Contributor
timestamp: July 26, 2019, 05:01:08 am
content: Is your building of recent construction? Several years ago we became the first owners of a newly-constructed apartment unit in a multi-family building that had radio telemetry built into an exterior wall (there was a blank faceplate cover that caught my attention).Inside was a battery-powered device that monitored various aspects of the building envelope weatherproofing integrity, historically a huge issue where I live in Vancouver, Canada, and I’m sure other rainy locales.I forget exactly how I figured it out, probably by looking up the chipset or the board manufacturers name, which was some kind of environmental sensing device supplier.Several times over the next couple of years I’d come home (or leave the apt.) and find a laptop sitting outside the door with an antenna hung over the door handle. I then realized it was communicating with the device in the wall, and it was actually the builder’s quality assurance rep collecting the data (humidity, moisture ingress, temp, air pressure, etc) to monitor the envelope for both warranty purposes and construction technique effectiveness.As an engineer, I thought that amazingly progressive, and didn’t object, as some might. I could see with my eyes (and online research on the device) that there were no privacy issues, and since nobody ever came to ask to replace the battery, assumed it would just die one day, its mission fulfilled after a few years. I sold the apartment after a couple of years, and don’t know if it was maintained or not after that, but I doubt it.Thought I’d share in case your building situation was similar.

author: Halcyon
author_rank: Unknown
timestamp: July 26, 2019, 05:13:53 am
content: Do you happen to have a florescent light out somewhere nearby that's trying to restart?Quote from: Dundarave on July 26, 2019, 05:01:08 amProbably a Zigbee or similar device. You find these low power, low bitrate battery powered sensors all over the place, even in commercial buildings if they are being particularly cheap.

author: james_s
author_rank: Super Contributor
timestamp: July 26, 2019, 05:24:33 am
content: That is an odd one, sounds too irregular to be a wireless thermometer or weather station. Smart meter maybe?

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 08:33:50 am
content: Quote from: Ampera on July 26, 2019, 03:50:11 amBeware! It's coming frominside the house!Quote from: Dundarave on July 26, 2019, 05:01:08 amVery interesting. Never heard of that. Thanks for sharing.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 26, 2019, 08:53:44 am
content: Could be anything but probably something with a bit of processing inside. Might use your mains wiring as antenna so the source could be somewhere else. Switch off your mains power and see if it is still there.

author: ogden
author_rank: Super Contributor
timestamp: July 26, 2019, 08:59:48 am
content: Quote from: Ampera on July 26, 2019, 03:50:11 amWay too many unknowns. You can search better than that. Switch off *ALL* breakers of your house, make it completely off-grid, check for EMI noise. If still present - contact radio frequency control authorities if concerned. If noise is gone when house is dark - do better search to narrow down list of the suspects. Power-up devices one by one until you find something.Quote from: PA0PBZ on July 26, 2019, 08:53:44 amRight. It could be power line Ethernet as well.

author: alanb
author_rank: Frequent Contributor
timestamp: July 26, 2019, 09:35:05 am
content: NSA Bug?

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 10:04:13 am
content: It could be some electronic device using power in spurts and the noise is coming from the power supply. Maybe a SMPS.Either that or crickets.

author: nali
author_rank: Frequent Contributor
timestamp: July 26, 2019, 10:07:48 am
content: Well that's smack in the middle of the ADSL spectrum (assuming your radio IS receiving at 570kHz and not an image).

author: Ampera
author_rank: Super Contributor
timestamp: July 26, 2019, 12:39:27 pm
content: Alright some other things it's not from the list of suggestions.My house is around 90-100 years old, and while a transmitter like that might be a culprit, what gets me about this is how it has such a tiny range.It is not an ADSL line doing strange things, because our house is fiber and twisted pair ethernet, and nothing besides one single ethernet cable (no PoE and no EoP).After some more fine tracing down of where the signal was strongest and weakest, I have made a discovery. The true epicenter of the transmission is our gas water heater, with the water pipes and gas line acting as one massive antenna. I have confirmed it to not be the gas meter, as that is outside, and the gas line closer to it does not have a stronger signal as compared to when I do it near the water heater.So now I do have a fairly decent idea of the source and general cause, but I'd find it interesting to know how a water heater (or hot water pump), both off or on, could make such a signal.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 01:22:05 pm
content: Does the gas heater have any electronics? If so, what happens if you disconnect them?

author: Ampera
author_rank: Super Contributor
timestamp: July 26, 2019, 01:47:40 pm
content: I'm gonna change my opinion a bit here, I do actually think it might be the electric meter.Walking outside with the radio and placing it near our two meters (we own a two family house), the signal drops and gains sharply if I so much as move it away from the meters. The interference could totally be moving along the mains wiring, maybe it's even blasting that interference through ground somehow, that would explain why the pipes were radiant sources of the signal.I did actually look if there was any known thing that these meters did to 570 AM, and while I didn't find anything for that specifically, I did find that two radio stations near me (I live near Albany, NY) broadcasting in NYC and Syracuse both operate on 570 AM, exactly where that signal is picked up. I also wish to note that the signal is actually present almost across the entire AM radio range, but in a much different form. It's the same pattern, but it doesn't have the same sort of tone, it's more white noise pulses than anything else, and is much quieter.Any thoughts?

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 26, 2019, 02:11:52 pm
content: Have you noticed if the picked up noise was there at all hours, every day, or if it appeared or disappeared depending on time and days?Have you noticed any possible link with the weather?

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 02:25:12 pm
content: Meters, electric, water, gas, etc, can communicate wirelessly usingzigbeeand other protocols. They form a network and can transmit from one to the next.

author: ogden
author_rank: Super Contributor
timestamp: July 26, 2019, 02:28:49 pm
content: Quote from: soldar on July 26, 2019, 02:25:12 pmUnlikely. Meters do not transmit so often.

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 26, 2019, 03:28:23 pm
content: Could it be the old on-peak, off-peak signals being sent by the utility?It will sometimes make ccfl lamps flicker and fan motors buzz to a tune. Maybe something funky is happening in relation to that?

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 26, 2019, 03:37:29 pm
content: I agree with a previous poster, on which the best method is to turn off all the breakers, monitor the signal, and the start turning them on one by one.If you find a particular breaker which causes the interference, now proceed to remove all the loads connected to the circuit, and repeat by connecting them one by one.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 03:55:01 pm
content: Quote from: ogden on July 26, 2019, 02:28:49 pmMy electric meter in Spain is transmitting continuously. The company knows what electricity I am using in real time. Nobody has come out to read a meter since this electronic meter was installed.There have been protests about this because it pretty much allows the electric company (and "associates") to know what you are doing, when you set the clothes washer, etc.The meter itself comes prepared with at least three different forms of communication but I believe in my case it uses PLC.https://www.landisgyr.com/resources/introducing-the-power-of-plc/https://eu.landisgyr.com/g3-plcThere are many meter communications systems:https://www.researchgate.net/publication/261197802_Survey_of_smart_metering_communication_technologiesMy guess is those chirps are packets of information being transmitted by the meter. Disconnect the switch or fuse before they meter and see if they stop. Disconnect a fuse or switch after the meter and they should continue.

author: james_s
author_rank: Super Contributor
timestamp: July 26, 2019, 03:57:39 pm
content: You might grab one of those cheap RTL SDR dongles and try using that, with a much wider frequency range you can try to locate the actual frequency. An AM radio will pick up images of signals that are way outside the selected band.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 05:07:31 pm
content: Just now they are talking in the news on TV that they are implementing a new billing system with six different rates during the day. Energy consumed just after midnight will cost less than half than energy consumed during peak hours.Nobody understands the electric bill anyway. They do it in such a way that no one can decypher it.发自我的华为手机

author: ogden
author_rank: Super Contributor
timestamp: July 26, 2019, 07:03:26 pm
content: Quote from: soldar on July 26, 2019, 03:55:01 pmAll meters behind transformer substation uses same communication channel, same frequency band. It means one can't transmit continuously because it must free channel for others. Meters themselves do not transmit unless they receive query from substation/hub. Most smart meters in Spain are ITU-T G.9904 - compliant. Standard is openly available, you can check yourself that you are mistaken in literally every of your claims.BTW meter reading power line communications uses < 500 KHz frequencies.

author: Ampera
author_rank: Super Contributor
timestamp: July 26, 2019, 07:42:40 pm
content: Some things:For one, this signal is continuous. I haven't staked it out to know for definite, but in the day I've noticed it, it's not changed at all.For two, there is no peak/off-peak billing where I live, all power is the same rate all the time, afaik.For three, I don't honestly know if this is specifically intended to be an AM transmission. I don't know the dynamics of AM radios being able to pick up things way out the normal band, just in a different way, and to be honest I hadn't heard that since before I made this thread.It's a bit tricky to just wham, turn off all the power here, I live with people, and we have servers running, so I'd need to make a good case as to why that's a good idea.I would love to get an SDR one day, and maybe I'll look for something of the sort, but for now I'm afraid the best piece of radio gear I have is one of those Grundig wind up camping/survival radios (they aren't bad little radios that being said).I think I'll do a bit more study of what it might be and some research, maybe try or investigate a few more suggestions. If there are any other ideas, please let me know, or if you want me to do something, like record a longer segment so that it can be studied, I'm perfectly happy to do that too.

author: nali
author_rank: Frequent Contributor
timestamp: July 26, 2019, 07:54:00 pm
content: If it's a point source rather than leaking from the household wiring you might be able to use your AM radio for a bit of direction finding if it has a ferrite rod of a decent length. Look for the nulls rather than signal peaks then the rod should be pointing towards the source (hopefully!).

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 26, 2019, 07:56:35 pm
content: Quote from: nali on July 26, 2019, 07:54:00 pmIt probably radiates using the mains wiring so good luck with that.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 08:21:00 pm
content: Quote from: ogden on July 26, 2019, 07:03:26 pmMy only claim was that there is a good chance those chirps coming from an electric power meter might be the meter transmitting information but since you feel the need to be so rude I'll just put you on my ignore list. Thanx and bye.

author: nali
author_rank: Frequent Contributor
timestamp: July 26, 2019, 08:28:06 pm
content: Quote from: PA0PBZ on July 26, 2019, 07:56:35 pmYou're probably right. But if the OP already has a DF device, why not?

author: ogden
author_rank: Super Contributor
timestamp: July 26, 2019, 09:10:42 pm
content: Quote from: soldar on July 26, 2019, 08:21:00 pmYou can't hear chirps of meter reading PLC transmissions on 570khz AM radio because those are using frequency bands way below 500KHz. Also most meter reading "standards" uses OFDM modulation which is wideband transmission. OP mentioned just single frequency, yet in case of OFDM one may hear similar packet pop/chirp pattern over wide range of frequencies. It can't be (A)DSL for same reason - because it uses wideband OFDM as well.Also you claimed that your meter is continuously transmitting and energy company receive consumption data in real time, those two claims are wrong as well. If you feel insecure when someone do not agree with you - then sorry. I stand by my principle - before you post/claim something, make sure you know at least absolute basics.

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 26, 2019, 09:24:15 pm
content: QuoteThat un-narrows things a bit. Do you know exactly what's plugged in everywhere?

author: SilverSolder
author_rank: Super Contributor
timestamp: July 26, 2019, 09:38:24 pm
content: Quote from: Ampera on July 26, 2019, 12:39:27 pmBased on this observation, is it safe to conclude that the interference is a magnetic field?Thinking about it further... if the wiring in the walls have been installed so that the hot and neutral are not close together, they will form a loop that can emit a strongish magnetic field... seehttp://www.emfs.info/sources/house-wiring/Perhaps even a small loop in the house wiring can be a strong "transmitter" of interference if the current in the loop is noisy from switching power supplies etc?Your AM radio might the only tool you really need to map out where the "open loop" in the house wiring could be...

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 26, 2019, 09:54:18 pm
content: Mains converters are usually either shielded or make one hell of racket all over the band. Though it could be LV DC-DC converter inside something (though again, usually wide band, just hold a radio up to the computer you are using now).It could also be the processor in something being noisy (though it would have to be something super simple at such a low clock speed, unless it's a harmonic). I once had a cheap set of little RGB speakers that had such a noisy processor (it's PWM system), you could not only hear it through a radio, but faintly out of the speakers themselves. Their own microcontroller interfered with the amp chip (I smacked in some bypass caps across it and that quieted them somewhat).

author: floobydust
author_rank: Super Contributor
timestamp: July 26, 2019, 10:28:31 pm
content: It could be coming in on the cathodic protection for the natural gas pipeline. I've measured around -8VDC at a few amps wrt water pipe ground. It could be supplied by SMPS which you are detecting, instead of old school rectifiers.There must be a "galvanic" or "dielectric" pipe union (electrically isolates) the incoming natural gas pipeline from anything contacting (mains) earth ground. You will find them at the gas meter but sometimes located at the natural gas appliance (hot water heater, furnace). I'm not sure what your codes dictate.A galvanic union prevents shorting out the (gas) pipeline's cathodic protection to mains ground, and for a hot water heater, it prevents the internal sacrificial anode from being consumed with them on teh water inlet/outlet.I mention it because it could be why the HWT is relevant, if it is wrongly plumbed.

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 27, 2019, 12:54:02 am
content: I highly doubt they'd connect a switching supply to a pipeline, aka a massive antenna. Unless it's super filtered, it would be incredibly noisy, maybe almost as bad as an old spark transmitter.

author: soldar
author_rank: Super Contributor
timestamp: July 27, 2019, 01:11:09 am
content: Quote from: Ampera on July 26, 2019, 01:47:40 pmIf you check the brand and model of the meter you can find online to see what kind of communications it uses. That's what I did,

author: floobydust
author_rank: Super Contributor
timestamp: July 27, 2019, 06:16:20 am
content: Quote from: Cyberdragon on July 27, 2019, 12:54:02 amPipelines are buried several metres underground and don't make great antennas. Cathodic protection power supplies are increasingly SMPS with no EMC standard followed.OP can shut off power to the home and snoop around with a portable AM radio. The energy meter will still be running though.

author: CJay
author_rank: Super Contributor
timestamp: July 27, 2019, 07:36:23 am
content: Quote from: floobydust on July 26, 2019, 10:28:31 pmI was typing similar about cathodic protection devices for building metalwork.I spent a day being interviewed at a company who made such devices for the protection of the metalwork in reinforced concrete and metal framed buildings, theirs was quite clever if it worked in the way they said it did but it was essentially a processor controlled low frequency PWM current source.