There is a very nice article in this months QST on building a very good
DFing antenna with more gain than a loop... See the cover.
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 3/21/21 5:01 PM, Gary wrote:
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@gmail.com>
Sent: Sunday, March 21, 2021 3:21 PM
To: Gary <gary_mayfield@hotmail.com>
Cc: rfi@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@hotmail.com<mailto:gary_mayfield@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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