repeating signal

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  • Updated 4 years ago
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Does anyone have any idea what this is?  The antenna jack is connected directly to a dummy load via a 6' coax jumper. If I remove the antenna coax, the signals go away. If I connect a real antenna, these signals are superimposed on the actual signals. They do tend to drift slightly up and down. 6700  - 1.6.17 - Windows 10
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Mark Erbaugh

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Posted 4 years ago

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Jon - KF2E

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Sure looks like a switching power supply to me.

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Kevin Va3KGS

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Morning Mark

I had a similar signal on different bands and found it to be my "smart" battery charger in the garage, and the other was the charger for the 12V back-up sump pump battery back-up system in the room next to me.  I put a timer on both of them.  I'm a happy DXer now!! 

Good Luck


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KY6LA - Howard, Elmer

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Suggest you read my how to build a quiet station
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Walt - KZ1F

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What I find amazing, and a little amusing, is before manufacturers started supplying visual spectrum displays we were all quite satisfied with little chirps, birdies, and other noises on the band we operated on. Myself included. Now, its as if the band is almost unusable.
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George Molnar, KF2T, Elmer

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HA! How right you are, Walt. The advent of the panadapter in my shack sent me on spasms of noise hunting and fostered neurotic obsession with every dB. Now, granted -- it made a huge difference. Didn't realize what I had been missing, I suppose.

Though, to be fair noise levels have demonstrably crept up all over the place. The sheer volume of consumer electronics and the change away from incandescent bulbs has made for a lot of RF out there. It's a sign of the times to say that the ham radio that used to interfere with other people's electronics is now getting interfered with BY other people's electronics.

I think I need a cabin in a remote, rare grid square.
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Dan -- KC4GO

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First read Howard's article!
My new tool to find the noise is a Kenwood TH-F6 handy talky it has a general coverage receiver with and internal antenna for SW and has a signal meter. Once you find the frequency with the Flex tune the Kenwood in and go around the house when it get full signal on the meter turn off the internal SW antenna and use the rubber duck until the signal is full again then remove the rubber duck and by the time it's full again you should be very close to the source...  Good luck on your hunting.  (any portable SW receiver will assist in  your Fox hunt) 
Dan -- KC4GO
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Mark Erbaugh

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I have read Howard's article and will give it another read.

I think I have found my noise source - it's the computer that runs SSDR!  I used another radio (K3 with P3 pan adapter) and saw the same repeating signal on it. When I turned off the SSDR computer, the noise went away.
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KY6LA - Howard, Elmer

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Likely cause is the switching power supply in the computer. Replace it with a high quality one from Corsair which are pretty quiet. Try putting torroids on all leads into and out of the computer. Make sure the computer case is a Farraday Cage. ...remove paint around the case screws so they make contact.
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EA4GLI - 8P9EH - Salvador

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Great advice. If you are getting a new supply, which I also recommend, spend a bit more and get extra watts over what you need and go Modular. I think just using the specific cables that you need for the devices inside the pc is ideal for better internal flow of air and less of a mess of cables.