 |
PM |  | |
Quote | | |
Reply | | |
Full Topic | |
| Joined: | Jun 5th, 2012 |
| Location: | Inverness, Scotland |
| Posts: | 85 |
| Status: |
Offline
|
The problem with the power line idea, is I am running this through a UPS so any fluctuations in power or any noise on the power line is smoothed by it. The mains power is always dirty in residential areas, so anything electrically sensitive (computers, HD TV's, bluray players, etc.) I have going through UPS units.
Besides, even if I did have this unit plugged directly into the wall outlet any high frequency noise would be removed by the ceramic caps, the low frequency noise would be buffered by the large caps, and any kind of hum or harmonics would be removed by the way I have the power supply ground setup. I scoped my power supply before I ever connected it to anything so that I know what the output waveform looks like, and it's a typical DC wave (none, just a straight line ;) ).
Good thought Jan, but it's just not it, that's why this is driving my up a wall.
My other thought is that it is actually a transmission from somewhere else (dimension, plane, reality, etc.) and we have no way to receive it. Like picking up a fax without a modem, it just sounds like garbage on the phone line. But then if this is it, that means we need to figure out how to demodulate it (any I'm not smart enough for that).
Jeremy
I'm not at all convinced that any power filtering completely removes this type of noise. It gets radiated DIRECTLY from the mains wiring, including the earth/ground wires. Filtering only reduces or stops it getting in directly via the wires. (I've seen these units communicating with each other without a direct connection. It was the sheer strength of the signals radiating from one mains circuit into wire a few feet away. Theoretically impossible!)
There all all manner of modes that this interference can couple into equipment without a direct connection. Your sensitive equipment is I think proving the point.
It's not hash from switched-mode power supply in any domestic equipment because your signal is not random. Do you live near a cell/mobile phone tower, or any establishment that may use pagers or remote security alarms? The UHF/microwave signals from these transmissions can sometimes break through into audio equipment.
Have look on Youtube for interference from power line adaptors. The sounds as demodulated by a radio are not identical to the sounds you have posted, but they are so similar I can't believe they are not related.
One example: http://www.youtube.com/watch?v=S__UBDaL-aE
It is still my bet that it's someone using a powerline adapter in your neighbourhood. It's quite likely that the signals in the mains won't be of sufficient amplitude to show up on a scope even before any filtering. And it also depends upon the bandwidth of the scope. If only this type of interference could be stopped with filters and ceramic capacitors...
There are groups in the UK (the RSGB and UKQRM) recording, measuring and trying to put pressure on the regulatory bodies to enforce the existing rules that stops the importation and use of this equipment, as it causes interference to legitimate users of the radio spectrum, and also causes more esoteric problems like yours. I'm sure your ARRL and FCC in the US has some examples on their website.
If possible run all your equipment from batteries and switch off the mains and see if that reduces the interference. Or try the experiments at another location miles away.
Good luck.
Jan