Interference (Audio clip included)

[NECRAT]

OK for the last couple of months we have been getting this very strange sounding interference. It typically hits in the FM Band, but occasionally it goes into other bands as well. Sometimes it will last for a couple of hours, sometimes it is a couple of minutes, but the noise is always the same.

It's a "pulse" of electrical noise that happens every 8-12 seconds.

To hear it, listen here:
http://www.necrat.com/skippy/noise.mp3

I've shut down everything in my apartment and still heard it.
I was going on the theory that it was my downstairs neighbor's computer. But she isn't home this morning.

Let me know if you have any ideas...

 

[Andy_Brown]

> OK for the last couple of months we have been getting this
> very strange sounding interference. It typically hits in the
> FM Band, but occasionally it goes into other bands as well.
> Sometimes it will last for a couple of hours, sometimes it
> is a couple of minutes, but the noise is always the same.
>
> It's a "pulse" of electrical noise that happens every 8-12
> seconds.
>
> To hear it, listen here:
> http://www.necrat.com/skippy/noise.mp3
>
> I've shut down everything in my apartment and still heard
> it.
> I was going on the theory that it was my downstairs
> neighbor's computer. But she isn't home this morning.
>
> Let me know if you have any ideas...
>

Do you also get this noise on a portable receiver or only receivers that plug in to house power?
<P ID="signature">______________
Electricity is really just organized lightning.
~George Carlin</P>

 

[Russty]

I have an old microwave oven that causes this kind of noise on FM. That may be a possibility. Microwave ovens don't send out a constant wave, but rather in shorter pulses depending upon the power of the microwave unit. When slow cooking something in the microwave the pulses are further apart in duration over a longer period of time. Cooking at higher power will have slightly longer pulses at shorter intervals. It's really quite interesting. But if you think that is odd, I also have an electric carving knife that causes snow on my TV screen. Hey, there is a good point. When you hear this interference, check and see what is happening on your TV. See if the sound and or the picture has any anomalies. Be sure to check the VHF channels (2-13) but check the UHFers as well. I once had a bad electrical High voltage line emitting wicked interference intermittantly in much the same way too. IT effected the FM a bit, but especially the picture on the TV in the VHF band. Suprisingly enough there was no odd noise from it on the AM band. IT turned out that the high voltage wire on top of the pole across the street from me had melted through its insulation, and was arcing to the uninsilated wire that was secring it to the insulator on top of the pole. This condition was rather intermittant, but most prevalent in wet or damp weather. You could actually hear it buzzing away on a foggy night, and coincidentally the interference was bad bad bad when the buzz was loudest. I called our local power utility and they found the problem, fixed it, and voila! no more buzz on damp nights, and no more interference, except for when the old lady cranks up the microwave. So, to make a long story short... If it is a random intermittent thing with bursts of varying lengths at varying intervals, it may be a utility problem. On the other hand, if it is regular pulses at regular intervals, it might be a microwave oven problem. Or it could be something else entirely different too. But at least these are two distinct possibilities to look into. Good Luck.

>
> It's a "pulse" of electrical noise that happens every 8-12
> seconds.
>
> To hear it, listen here:
> http://www.necrat.com/skippy/noise.mp3
>
> I've shut down everything in my apartment and still heard
> it.
> I was going on the theory that it was my downstairs
> neighbor's computer. But she isn't home this morning.
>
> Let me know if you have any ideas...
>

 

[robojock]

> >
Are there flourescent lights where this thing is plugged in? If so does it seem like the ballasts in any of them are going bad?

OK for the last couple of months we have been getting this
>
> > very strange sounding interference. It typically hits in
> the
> > FM Band, but occasionally it goes into other bands as
> well.
> > Sometimes it will last for a couple of hours, sometimes it
>
> > is a couple of minutes, but the noise is always the same.
> >
> > It's a "pulse" of electrical noise that happens every 8-12
>
> > seconds.
> >
> > To hear it, listen here:
> > http://www.necrat.com/skippy/noise.mp3
> >
> > I've shut down everything in my apartment and still heard
> > it.
> > I was going on the theory that it was my downstairs
> > neighbor's computer. But she isn't home this morning.
> >
> > Let me know if you have any ideas...
> >
>
> Do you also get this noise on a portable receiver or only
> receivers that plug in to house power?
>

 

[TPO]

You are on the right track by killing the power to your apartment to see how localized the problem is. Try using a portable FM radio to see how widespread the problem is. Is it just in your building or does it extend into the street and down the road?

The other folks have had some very good ideas. Other common causes of interference are fish tank heaters and anything with a switching power supply, which is just about everything electronic these days. Keep in mind that just tunring off suspect appliances doesn't necessarily mean that the unit is really off. Often the power supplies remain on when the power switch is off so make sure you unplug when testing.

Electronic light dimmers, celing fans (esp. those with electronic speed controls) and those little night lights with built-in photocells are well known RF generators, but that interference tends to be more continuous and usually affects the AM band as well.

If you are in the country, look for defective bug zappers and electric wire fences that are shorting to brush, have a bad insulator, etc.

If you are in a commercial district, look for neon signs, large gas air conditioning units and even electronic cash registers (which often put out birdies in the VHF band that radiate for hundreds of feet).

Good luck and let us know what you find.