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Strange mains waveform/"rattling" noise

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Kizmo

Thu Feb 07 2008, 11:11PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Got it!

Its not very good picture but it gives idea.. 1V/Div @ 1ms / Div

EDIT:
better one:

Proud Mary

Thu Feb 07 2008, 11:49PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

These are the control frequencies injected into the mains supply for remote device switching by VDEW - the main German electricity supplier. I would guess the Czech grid is connected to it, so this could explain some of the things you are hearing

Frequency [Hz] Bandspread [%] Amplitude [%]

110 1,7
168 -0,5...+0,5 1,7
175 -0,5...+0,5 2,5
183,3 -2...+1 3
190 -0,5...+0,5 2,5
194 2
206 2
216,7 -2...+1 3
228 2
232 -0,5...+0,5 1,7
267 -0,5...+0,5 1,7
270 3
283,3 -2...+1 3
316,7 -2...+1 3
383,3 -2...+1 3
425 -2...+1 3
485 4
582 4
600 -2...+1 4
725 4
750 -2...+1 4
1050 -2...+1 3
1350 -2...+1 3
1600 -2...+1 2,5

EDF (ElectricitÃ© de France) uses a system of remote control called PULSADIS which can remotely change meter tariffs and initiate street lighting and so on. The PULSADIS carrier injected into the mains supply is at 175 Hz with an amplitude minimum of 0,9% of the nominal voltage of the sector, that is to say 2,3V. It uses a binary pulse code to create 20 control channels for remote switching.

Nik

Fri Feb 08 2008, 01:07AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

Last summer I had a "problem" kind of like this. Some of the speakers in my house (some of them disconnected) as well as the filaments of light bulbs would buzz faintly in a pulsing way that sounded similar to talking. From 10 pm to 11pm this would happen almost every day then it stopped and hasn't come back. Im pretty sure it is/was interference from a local ham radio (they pump out some serious power eventhough its a residential area). Im still curious as to why I could hear it in lightbulbs.

Proud Mary

Fri Feb 08 2008, 10:49AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Nik wrote ...

Last summer I had a "problem" kind of like this. Some of the speakers in my house (some of them disconnected) as well as the filaments of light bulbs would buzz faintly in a pulsing way that sounded similar to talking. From 10 pm to 11pm this would happen almost every day then it stopped and hasn't come back. Im pretty sure it is/was interference from a local ham radio (they pump out some serious power eventhough its a residential area). Im still curious as to why I could hear it in lightbulbs.

Problems of this kind are sometimes caused by local megawatt radar installations. The buzzing sound is at the pulse repetition frequency. The most bizarre case I recall was about twenty years ago, when a man living in Cornwall [England] complained of buzzing in his teeth. It was at first assumed that this was a mental disorder, but later found to be due to the formation of a rectifying junction by the amalgam fillings in his teeth!

The sonic effects you report in light bulbs are likely due to thermal expansion and contraction of the filament as current flows, and perhaps also to magnetostriction. The human ear is very insensitive at 50/60Hz so one doesn't notice the effect in normal operation of light bulbs, but at higher frequencies it may become noticeable.

Chris Russell

Fri Feb 08 2008, 08:19PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Hams in Canada are limited to 2.25kW of peak power. A fair amount of power, but an order of magnitude less than the average power of a broadcast station -- and amplifiers that can put out that much power are pretty rare and expensive. Usually, anyone running this much power will be pretty easy to spot, due to the large towers and antennas that one uses in conjunction with that much power. 100W peak is a much more typical power level for most hams. If I have an antenna close to the house, and it is poorly matched, some RF can get back into the house and cause a little noise on stereo systems that are on. I can't even imagine how much power it would take to interfere with a light bulb, or an unplugged speaker!

At any rate, if you ever experience similar trouble, it's a simple matter to go knock on his/her door and have a chat. Hams are generally very nice folk who will carefully work with their neighbors to resolve any interference complaints. Hams unfortunately have a long history of being suspect number one for interference of any kind -- a sad situation, since hams are often the first people to track down and eliminate interference, let alone cause it. You'll find that most of them will jump at the chance to improve the public opinion of the hobby.

Nik

Sat Feb 09 2008, 12:27AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

The antenna tower is about 50feet tall so there is probably a whole lot of power behind it. His voice also used to come over the tv clear as day until we switched from cable to satilite tv.

Chris Russell

Sat Feb 09 2008, 06:14AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

You might be surprised -- not many hams run near the legal limit. If you have any interference problems at all in the future, I would urge you to talk with him. As I said, most hams are eager to resolve any interference problems. After all, RF that's getting into your house wiring is RF that's no longer available to make contacts.

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