[RFI] New Interference at kk0sd

Sun Mar 21 20:01:07 EDT 2021

Don,

                Thanks for the suggestion. The 847 in the video does two meters in all modes. A swing of the 2 meter beam yields no noise. I can tune down to the airport VOR signal on 118 MHz and copy it clearly with no noise.

                I have a portable shortwave receiver and a loop antenna that served me well in tracking other issues, but I am not hearing the signal with my portable shortwave receiver and loop. I am not hearing it with the telescopic antenna either. I have a shortwave receiver in my pickup as well. I do not hear the noise when driving the neighborhood, so I figure it must be close…

                I have an MFJ-852 receiver it seems to go wild when broadside to either of my neighbor’s houses, but stays pretty quiet near my transformer box in the back yard.

                I will look into building a flag antenna for my portable shortwave receiver. I think it is a good next step.

                My utilities are underground so there aren’t really poles to check. I have tried the loop near all the boxes I can find with no results yet 😊

73, Thanks and Keep the suggestions coming!
Gary “Joe” kk0sd

From: Don Kirk <wd8dsb at gmail.com>
Sent: Sunday, March 21, 2021 3:21 PM
To: Gary <gary_mayfield at hotmail.com>
Cc: rfi at contesting.com
Subject: Re: [RFI] New Interference at kk0sd

Hi Gary,

I never like to guess what the source of the RFI might be, but here are some comments and suggestions.

Do you have a 2 meter beam and a 2 meter radio with AM mode capability?  If so you might be able to hear this noise from your house since it appears very strong on 20 and 15 meters.

I did a quick analysis of the audio in your recording, and it's possibly arcing (or switching) which is typically happening at 120 Hz (one time each half of the sine wave) but sometimes only at 60 Hz, and every other half cycle looks similar to itself (like something is breaking down easier during one half of the sine wave versus the other half of the sine wave).  The arcing is also intermittent (sometimes no arcing/switching during the time period of successive 60 Hz sine waves as an example).

Just because you don’t hear it on the AM broadcast band or 160 meters from your location does not mean it’s not power line RFI.  The more I track down power line noise the more I’m amazed how band specific it can be when not close to the faulty pole.  If you have a cheap portable AM radio you probably will hear this junk when you get closer to the source.  Using a cars AM radio can be hit or miss depending on the design of the radio, as it appears modern car AM radios have gotten much better in their noise blanker technology (I can hear arcing from a faulty power pole at great distances using the AM radio in my 25 year old Saturn, whereas I often can't hear any arcing when right next to a faulty pole in other vehicles that are more modern than mine).  I suspect you will be able to hear this on 135 MHz AM when you get very close to the source if you have an HT that tunes down into the aviation band where the radio would switch to AM mode or if you have a cheap hand held police scanner capable of 135 MHz, etc.

If you have a portable HF receiver I suggest you build a portable flag (see March issue of QST) and you will likely find the source of that noise (or narrow in on its location) very quickly since it appears to be very strong.  It’s appears so strong on 20 and 15 meters in your video that you probably will not even need a preamp with the portable flag.  You should be able to hear that noise from your yard and then walk right toward it using the portable flag.  As you get close to the source you will likely need to reduce RF gain or insert attenuation.  If it’s power line noise you might need to use 135 MHz AM with directional antenna when you get very close to the pole to isolate the pole from adjacent poles, and again would need attenuation (this assumes its a pole and not an in ground feeder, etc).

Just some thoughts from my end.

73,
Don (wd8dsb)

On Sun, Mar 21, 2021 at 2:02 PM Gary <gary_mayfield at hotmail.com<mailto:gary_mayfield at hotmail.com>> wrote:
My last problem was tracked down to a neon sign in a neighbors garage. I had several months of blissful relatively low noise operation, but now have a new RFI issue.

You can see a recording of it here:
https://www.youtube.com/watch?v=GKf4P44FXMo

I have turned all of the breakers in my home off and run the radio from a battery and the noise remains.

My neighborhood utilities are all underground.

There are no solar installations in my neighborhood, and the noise is there at night anyway...

The noise is not detectable on the AM broadcast band, but starts around 2 MHz and runs to at least 6 meters.

It is there 7 days a week 24 hours a day.

It is not detectable from my pickup when I drive the streets of my neighborhood (checking both AM broadcast and Shortwave).

If any one has heard something like this, I would love to hear what you found.

Thank You for your input and help!

73,
Gary "Joe",  kk0sd

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