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Author Topic: Can someone identify this noise?  (Read 267 times)

GREYLINE

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Can someone identify this noise?
« on: July 12, 2022, 11:39:25 AM »

This noise pops up on 20m at random times. Occasionally I see a trace of it on other bands, but not as bad as 20m.  I shut down the power to my house and ran the rig off a generator but it still happens. I don't know if it's possible to identify the type of noise this is simply from this photo, but if someone with more experience than me recognizes it, it would give me a good place to start.

Thank you.




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K5LXP

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Re: Can someone identify this noise?
« Reply #1 on: July 12, 2022, 11:45:50 AM »

It's almost surely a switching power supply. If you can run the rig off a battery that would eliminate anything else that might have been powered by the genset.  First thing I would try after that is to see if I could pick this up on a handheld AM receiver you can DF with.  Lowering the frequency might allow picking it up with a smaller antenna.  From there (generally) the higher in frequency you pick up the source the closer you are to it.  I've started with the interference picked up on 80M and 25 feet away I was hearing it on 2M.  Noting when you do and don't hear the noise can be a clue too (24/7, day/night, hot/cold, dry/wet, etc).

Mark K5LXP
Albuquerque, NM
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GRUMPY2021

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Re: Can someone identify this noise?
« Reply #2 on: July 12, 2022, 11:47:02 AM »

Well it's not in your house.   So what you need to do is look out the biggest window you have.   It's out there somewhere.    ;D ;D ;D ;D

Seriously is it happening day or night?   I had noise that only showed up towards dusk.   Looking way down the street I could see a street light that was out.   They later told me the noise I was probably hearing was the senors trying to turn the light on all night long and then during the day it all stops.   Good luck finding your needle...

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GREYLINE

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Re: Can someone identify this noise?
« Reply #3 on: July 12, 2022, 12:19:10 PM »

Thanks for the quick reply, guys. The noise pops up at random times throughout the day and night, but seems to disappear after 10pm or so (if I remember correctly). When I ran the radio off the generator, the only other thing that was plugged in was my Astron power supply that powers my Array Solutions RatPak remote antenna switch. Astron PS's have a reputation for being quiet so I eliminated it as a source. Just to be thorough though, I should probably run the antenna directly to the radio.

I also have an RF-Pro-1B magnetic receiving loop. The noise is still present and I can't seem to null it out by rotation the loop. I also rotate my tribander but the noise is present in all directions. This might indicate that the source is CLOSE (?)
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W9IQ

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Re: Can someone identify this noise?
« Reply #4 on: July 12, 2022, 12:55:17 PM »

The Astron linear supply should completely RFI mute. I agree that you should eliminate the remote switch, particularly if you use any of the 'smart' control heads.

Are you using the same antenna on all bands? The RFI could be frequency dependent based on the antenna. The 10 kHz spacing indicates it should have a quite wide-band RFI. Do you have common mode chokes on the 20 meter antenna?

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

GREYLINE

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Re: Can someone identify this noise?
« Reply #5 on: July 12, 2022, 01:29:28 PM »

The Astron linear supply should completely RFI mute. I agree that you should eliminate the remote switch, particularly if you use any of the 'smart' control heads.

Are you using the same antenna on all bands? The RFI could be frequency dependent based on the antenna. The 10 kHz spacing indicates it should have a quite wide-band RFI. Do you have common mode chokes on the 20 meter antenna?

- Glenn W9IQ


I'm using the Baluns that came with my JK Antenna. One for 10-20 and one for the 2 el 40m on the same boom. The noise is still present on my 43' vertical AND my small Rx loop.

When I get a chance I will bypass the remote antenna switch and run an antenna directly to the rig.

Thanks for your input.
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W9IQ

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Re: Can someone identify this noise?
« Reply #6 on: July 12, 2022, 02:16:05 PM »

For receive RFI issues, a second common mode choke just before the coax enters the shack, is a best practice. It should be between the ground connection and the antenna.

Use a choke with an Rs > 4k ohms.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

WA3SKN

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Re: Can someone identify this noise?
« Reply #7 on: July 12, 2022, 02:32:36 PM »

Step one... replace antenna with a known good dummy load... verify you lose the noise.  This verifies it is incoming via the antenna.  If not, replace power supply with a battery... then you can eliminate the power supply as the culprit.
Then you can start throwing breakers... it sure sounds like a local noise source in the area.

-Mike.
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W9IQ

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Re: Can someone identify this noise?
« Reply #8 on: July 12, 2022, 02:37:00 PM »

Step one... replace antenna with a known good dummy load... verify you lose the noise.  This verifies it is incoming via the antenna.  If not, replace power supply with a battery... then you can eliminate the power supply as the culprit.
Then you can start throwing breakers... it sure sounds like a local noise source in the area.

-Mike.

Unfortunately, the dummy load test does not eliminate transmission line or related connector problems. A fraction of an ohm in either coax conductor path will still allow RFI to be received when a dummy load is connected at the distal end.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

N7EKU

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Re: Can someone identify this noise?
« Reply #9 on: July 12, 2022, 05:13:02 PM »

Hi,

Probably the easiest quick check is to take an AM pocket radio out in your yard.  Tune it so it is not on a station and picks up the noise the best.  Make sure you know how the ferrite rod loopstick antenna is oriented inside the radio. Now hold the radio so the loopstick is horizontal and rotate the radio around.  If the noise is from a point-source there should be two orientations where the noise is nulled out.  If it does this, then at the null the noise source should be located in line with the loopstick.  Start walking and see if you can pin point the noise.

I did this when I had a regular 12h cycle of noise starting the same time everynight.  It was grow lights on a timer from some friends of Cheech and Chong about a block away.



73
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Mark -- N7EKU/VE3

WA3SKN

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Re: Can someone identify this noise?
« Reply #10 on: July 13, 2022, 11:57:59 AM »

I normally connect the dummy load directly to the radio first.

-Mike.
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