Can anyone identify this QRM?

[brandon]

Lately I have been getting this strange QRM at my location. It's a buzzing noise with whining high pitch beeps every 3 seconds. Definitely man made and unfortunately wipes out large portions of the band, so I'm anxious to get to the bottom of it. Here is an audio sample hoping somebody can help clue me in on what may be the culprit.

Audio sample: http://www.solarix.net/audio/qrm_20100401_130536.mp3

I'll see about capturing a screen shot from SpectraVue waterfall display when I get home if that may help.

 

[zz0468]

Hi Brandon. Whatever it is, it sounds like incidental radiation from some type of computer or computer controlled device. It certainly doesn't sound like any type of legitimate signal.

I can't say I've heard anything absolutely identical, but I've heard similar types of noise coming from things like video game consoles, VCR's, DVD players, and Satellite TV receivers.

 

[k9rzz]

Did this just start up? What frequencies? Times? I can't nail it down, but I'm thinking powerlines. There's some new technology that sends digital information down powerlines for controlling switches or something. I ran across it once while mobile. Not sure though, just a hunch.

 

[jwb8734]

Have you also tried to match it up to something on
Digital*Modes*Samples

 

[E-Man]

No idea what could be the culprit? Its been a couple years since I have worked in your area, the only thing that comes to mind may be Edison's new Smart Connect Meters that I am not familar with. Have they rolled them out in your area yet? I hope these are not the culprit because they may be everywhere in the future.

SCE - A Smarter, Cleaner Energy Future with our Customers

 

[SCPD]

Yep, definitely sounds like consumer electronics. Try turning off any Wi-Fi routers, ethernet hubs, computers, HDTVs, etc.

Try a portable in your immediate room to see if it's loud or not. If not, then it's probably external to your area. Worse case scenario, it could be coming from your neighbors. You may have to take a portable SW radio and track it down.

It definitely doesn't sound like a digital HF mode.

What frequency is it? If it's in the 11-15mhz range, then I would guess some kind of ethernet device. If it's 7mhz range then it's HDTV. (My LCD has hash-noise around 7mhz.)

 

[brandon]

Last night when I got home the noise was gone, however it was back when I checked this morning. I don't know if it's present during the day, but this weekend I'll be able to find out. Frequency wise it can be heard from the 160 meter ham band all the way up through 15 MHz. Seems to get weaker as you move up in frequency, but quite strong on the 5,6 and 8 MHz aero bands. First noticed the QRM about a week ago and figured it may be just temporary, but since hearing it a few more times I'm starting to worry. Thanks for the tips everyone.

 

[SCPD]

Yeah I would guess a HDTV. Some of the plasma models tend to be very broadband noise sources.

 

[k9rzz]

Last night when I got home the noise was gone, however it was back when I checked this morning. I don't know if it's present during the day, but this weekend I'll be able to find out. Frequency wise it can be heard from the 160 meter ham band all the way up through 15 MHz. Seems to get weaker as you move up in frequency, but quite strong on the 5,6 and 8 MHz aero bands. First noticed the QRM about a week ago and figured it may be just temporary, but since hearing it a few more times I'm starting to worry. Thanks for the tips everyone.

Continuously? or on discrete frequencies?

 

[brandon]

It was spaced x number of kHz (don't remember the exact though) but when I hear it again I will post a screenshot from SpectraVue.

 

[datainmotion]

It was spaced x number of kHz (don't remember the exact though) but when I hear it again I will post a screenshot from SpectraVue.

The interference from my plasma is spaced evenly apart, but the audio is nothing more than the buzz from the horizontal sync / video carrier.

Plasma makes sense with the broadband RFI, but your signal sounds more like a timed process.

 

[zz0468]

...but your signal sounds more like a timed process.

Clock signals radiating off a circuit board or cable?

 

[brandon]

Here are some screenshots that display the QRM as it appears from SpectraVue and Winrad.

190 kHz view from SpectraVue


50 kHz view from SpectraVue


190 kHz view from Winrad


Click on the thumbnail for full size view.

 

[brandon]

For what its worth the noise blanker is able to null it for the most part.

 

[kc2rgw]

Looks a lot like the signature of a switching power supply/battery charger.

You add any new electronics of any kind to the house recently? If this just 'popped up' I would look into that.

Since it's so broad banded, the signal must be strong, if you have an HT with AM mode, pop it into AM mode on center of one of the offending bands and start wandering the property.

Also, you could rule out your own home by shutting down all breakers other than the one powering your receiver. If it goes away, start bringing up your breakers one at a time until you find the circuit that brings up the noise.

I have a wheelchair battery charger that does this ...dueling broad bands that show up on many many bands as harmonics. I can tell when the battery is getting near charged as the modulation cycle of the charger becomes more rapid near the end of the cycle and I see the bands move in frequency...but stay parallel in offset.

I also have a Roomba vaccuum in the house and it's charger does a similar thing, but much lower in amplitude.

Over time, particularly using SDR, you get to unfortunately know all the quirks of your own and your neighbors' gear.

 

[kc2rgw]

What is the radio you are using with WinRAD? Also have you tried WinRAD HD yet Homepage WinradHD by DG0JBJ the -fs command line option stretches to wide screen monitor format very nicely. It will also run in 'window' mode with another command line flag.

 

[kc2rgw]

Gaaah, just listened to the sample, that's not a power supply.

Something with wireless communications for sure as that is telemetry of some kind.

Wireless mouse, wireless keyboard etc etc. Anything new that is wireless should be suspect.

 

[datainmotion]

If I didn't know any better, I'd say it sounds like a dot matrix printer.

There are 24 high pitched tones seperated by 6 "ticks" between tones in the recording. The change at 0:49 sounds like a carriage return.

 

[brandon]

Unfortunately the noise appears to be permanent now. Since Tuesday it has not disappeared like it did in the past. One thing I noticed it sounds a little different now. Nothing new electronics wise has been added so this is either coming from the neighbors or something else in the area.

Examples below are near 520 kHz which seem to be where the QRM is the strongest. It's spaced upwards about every 100 kHz or so.

Sample 1 - Buzzing (mp3 audio)


Sample 2 - Power lines? (mp3 audio)


No portable radio here, so DF'ing is a bit of a challenge. I did try the car radio and don't hear the noise, so it gives me hope that this part of the property can be used for the antenna relocation if all else fails. hi hi.

 

[k9rzz]

THose last two are from different sources. First sounds kind of digital or electronic in origin, second one is a leaky power line insulator or such, pretty classic. Plus, those are different from your original clip, so, you've got three different sources to get rid of.

I hate to say it, but you live in a noisy area my friend!

#1 Make *SURE* that you're not generating any of that yourself. Save yourself some gray hairs.