Your thoughts on this interference while I hunt it down?

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  • Updated 3 years ago
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Hi all,

Before I go through the house again with my HT (first attempt was unsuccessful), would like your feedback on the nature, type and perhaps how to narrow down this interference.  Net:
1) Occurs on EVERY band
2) Is present when connecting any antenna, not present without antenna
3) Becomes less obvious during the evening

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Rob (N4RLM)

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Posted 3 years ago

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David Vernier

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This looks very similar to the noise generated by my ceiling fan...
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Rory - N6OIL

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Hi Rob, one question because I was seeing the same thing, do you have any battery chargers plugged in? In my case I had one, it turned out to be the power center on my 5th wheel trailer that I keep hooked up here at the house. Other spurs I get are from my washing machine, a Duet with VFD motor.
(Edited)
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Danny K5CG

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Laptop power supply/charger.
USB interface on a PC.
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Bob Craig, K8RC

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Looks very much like a variable speed drive on a HVAC air handler motor.
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Burch - K4QXX

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My air conditioner does this.  Wish I knew a way to stop it.
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Bob Craig, K8RC

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Check with your HVAC service people. Filter kits are available.
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Burch - K4QXX

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I was googling HVAC filter kits online and my searches come back as AC air filters.  Is there anything specific I should ask my AC guy? 
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Bob Craig, K8RC

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Sometimes Google gets stupid because it doesn't look for definitions 2 or 3 of the words.

Tell the HVAC guy that your motor drive is creating RFI to other radio equipment on the premises. If he doesn't understand any part of that statement, you need a different HVAC guy.

Check to see if the manufacturer has any information.

What you're looking to do is de-couple the drive from the power wiring (remove the transmit antenna from the QRM generator).
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Chris DL5NAM

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Switching power supply or radio based weather station.

If you can use a car battery for your Flex (or any battery driven radio like FT817), switch ALL fuses in distribution panel OFF. If noise gone switch step by step each fuse ON. You will found.
If all fuses OFF and noise further exist --> neighborhood

I am sure: noise device is label "Made in China"
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EA4GLI - 8P9EH - Salvador

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My process exactly when hunting for noise sources.
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WA2SQQ

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My step 1 is to figure out what it isn't. Start turning off 1 breaker at a time in your own house. If you find one circuit that eliminates it, you know where to start looking. If you don't find anything, than you can safely conclude that it's not something you own.

If you can run the Flex off of a battery an use a laptop, you can also shut the shack down to verify if it's something really close.

Have you tried a random length of wire, indoors, to see if it receives it? If it's in your house that indoor wire might receive the signal even stronger.

My biggest offender has been "wall warts" - many use switching power supplies and they radiate all kinds of noise.
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Andrew Russell

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I "got one" just yesterday on 40. Tracked it down to a blue ray disk player. Not the fat snake this time, though it was the antenna. A ferrite toroid, several turns in the low voltage lead and the noise is gone. 
Andrew VK5CV.
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Mystery Ham

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I'm with WA2SQQ with regard to shutting down the house, however I'd shut off every breaker except the one required for your flex and computer... It saves a lot of  running back and forth in the event it is not a device on those circuits. (sometimes breakers for  AC are located outside) . 

Searching with an AM radio can be tricky, If you have an HT that can do AM general receive, tune it to one of the noise frequencies and then take a walk around.

Going from a switching power supply to battery on my Flex nailed 80% of my parallel squiggly lines across several bands.

Beyond shutting down the house,  If it's still there, power off the monitor and power it back on again to see if there is a gap in the noise on the waterfall.  In the case of a laptop, disconnect the power cord from the wall.  If that doesn't do it, make sure your laptop is set to stay on when the lid is closed and close the lid to turn off the display and open it again to see if there was a gap in the waterfall.  Disconnect usb devices, including mouse and keyboard.

Flex connected directly to your pc via ethernet? try going through a router.  Going wired from the computer to the router, try wireless.  Using a PC?  Shut it down and try a laptop.


Once you identify the noise source, let us know...  I'd love to hear about it.

Mystery Ham
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AA0KM

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I get both those signals off and on anytime on any band.

I have run battery everything and signals still there.

Beyond my control away from the house here in the mid-west.

I wish you luck finding.

73 jeff


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Scott N8UMW

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I had a similar issue. Mine were all on higher bands, but same type of evenly spaced birdies. It turns out my computer monitor was doing it. I went from the HDMI input to the VGA input. They came up in different spots, but we're still there. I tried two other different branded monitors with similar results. For kicks, I tried a 22 inch lcd television. Problem solved. It was a 720P set and didn't look very sharp, so i picked up a 23 inch Vizio razor E 1080P set and used the HDMI input. Excellent as a monitor and noise still gone. One thing to check out. Just my two cents.
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Michael Coslo

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I'd bet a power supply/wall wart. This looks a lot like the RFI from my HP printer's power supply. Time to go around unplugging things, and you might get a person to help since the culrit can be in any room in the house.
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Mystery Ham

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One more thought since it's more pronounced during the day... ( wish I could tell the scale per division in your two photos)  MPPT controller for solar array?
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Steven G1XOW

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If the sig is there 24/7 then you can rule out solar inverters and LED lighting. The most common cause is a switchmode PSU in something.  Don't forget they get it to everything these days, not just wall warts!   Even Routers, switches, TV, HIFI, DVR, PC, laptop, monitors, CCTV systems have them. My friends "smart fridge/freezer" even has one.

Can you turn the beam and get a rough peak heading (higher bands would be better)?   My 4 ele SteppIR is shockingly accurate even on sources less than 50 feet away.

My technique for tracking down any "in-house" stuff: get someone to sit at the waterfall display so you can go walk about (you are more likely to see all the possible causes that a non-tech). Go around each room one by one and turn off every device in turn whilst keeping in touch with the person at the waterfall via mobile phone. Make sure they tell you of ANY change in the characteristic of the display.

Also note that changing the load (e.g. unplugging a phone from its charger) should show in the waterfall, and don't forget that PSU with large capacitors could take-10-20 second to disappear so don't be too quick to discount things.

73 de Steve G1XOW
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Rob (N4RLM)

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Official Response
Thanks to all the ideas - most helpful!  Traced it down to a couple of things:
  • DirectTV Wireless Transmitter wall wart
  • Fan inside NetGear Pro Router in the wiring closet
Fixed the DirectTV by moving it and the NGPro by replacing it with a non-fan PoE version.  Much better today!  Thanks again all!
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Mystery Ham

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Congrats!  now you  can focus on the less annoying ones!  :-P

Mystery Ham

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