Does anyone know what this is? They are spaced 20kHz from each other.

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  • Updated 4 years ago
these appear on 20 meters in the afternoon mostly, but have seen them at night.
just wondering.
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Bob G W1GLV

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  • good.

Posted 5 years ago

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Stu Phillips - K6TU, Elmer

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My guess is these are either from a switched mode power supply or more likly, from a variable speed motor controller.

The VSC usually are wider apart (60 - 80 KHz) and can be very strong - if you zoom in, and look closely, you may get more of a clue.

A switcher will show a fuzzy set of carriers when you zoom in and they will drift...

The VSC's I've seen have 60 Hz carriers when you zoom in and are very stable.

VSCs are used as energy savers on pool and well pumps.

Although its fun to speculate about waterfall signatures on RFI, the only real solution is to hunt them down and isolate the offending source.

Good luck!  These things can be really annoying!
Stu K6TU
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Dave - WB5NHL

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Bob; take a look at your air conditioner. I see similar signals radiated from my efficient air conditioner. Modern air conditioners use VSC's for energy savings. Good luck killing the signals. I have tried cable shielding without luck. The actual electronics is pretty well inclosed. So far I'm living with them at about 105db.
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Robert -- N5IKD, Elmer

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I call them birdies. And if they come from the neighbors, then they could be difficult to find.

I would like to put the radio on a battery, connect my laptop, and cut off the power to the house and the UPS-es, then turn each circuit individually until I catalog the birdies that I am creating. Some of them do seem to slowly creep along the panadapter, so they are not necessarily at fixed locations. If you zoom out you will see that they are stronger at one point and fade out toward the ends.
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James Kirk

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V'Ger
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Bob G W1GLV

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I would like to thank everyone who responded to myinquiry. The culprit is my new A/C unit which has VSC'sin it. I stopped it and the birdies went away. Thanks
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Ken - NM9P, Elmer

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That was a very quick trace. We'll done! I have noise sources that I haven't found in months!
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Alan W4FBI

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VSC's???
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Dave - WB5NHL

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variable speed controller
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Alan W4FBI

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i knew that ... not

thx Dave
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Stan - VA7NF

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You are lucky!  My VFD (variable frequency drive), which seems to be the earlier name for VSC, was so strong it was s9+20 on 40M and wiped out the airport beacon at 350Khz.  It took two line filters, hammond electrical shielding box, shielded 3 phase wiring, and an isolated ground.  It was only a 1HP motor.

Just happened my entire back yard lighting wiring (aka long wire antenna) was on the same circuit.