I added the pictures to the link. Tnx.
Don, your comments so closely align with my thoughts it is almost like I wrote
the comments. I did think this was a PLN issue, and we cleared a major issue
about .8 miles away, but that did not clear the issue. We have run RFI Maper
looking for PLN in the area many times but nothing of the right intensity shows
up. Have also done a lot of VHF investigation, but nothing conclusive. This
issue is actually in Rhode Island so I am not able to do it in person (I am in
GA), but I have a couple of partners on site doing the leg work.
It is great to listen to the input of so many experts. In addition to solving
this issue, I am expanding my thought on RFI investigation.
More to come.
From: Don Kirk <wd8dsb@gmail.com>
Sent: Tuesday, November 25, 2025 8:10 PM
To: jim@audiosystemsgroup.com
Cc: Jeff (W4DD) <w4dd09@gmail.com>; Rfi List <rfi@contesting.com>
Subject: Re: [RFI] RFI Signature
Hi Jeff,
Per Dave's (W0LEV) request I have attached 2 pictures. One is the oscilloscope
display of your noise which I called "RFI being investigated" when you were
using 20 KHz bandwidth. The other picture is using the same scope set up to
view the audio from my SDR receiver of a known bad power pole that was
typically arcing 2 times per each half cycle of the sine wave (again using 20
KHz bandwidth), and this was verified using a Radar Engineers Model 243
(typically 2 arcs per each half cycle). You will see in my known bad power
pole screen capture you have big peaks in the positive direction each half
cycle of the sine wave where I'm not necessarily seeing that in your screen
capture of your RFI being investigated (but it might be an optical illusion
based on the 60 Hz sine wave I injected on channel 2 which is not necessarily
in sync with the RFI being displayed on channel 1). You will also see an odd
gap in the positive peaking pattern on your RFI being investigated. On channel
2 of the scope (blue trace) I injected a 60 Hz sine wave just to help visualize
time relative to a 60 Hz sine wave and it's not necessarily in sync with the
RFI being displayed but it helps visualize the time relative to a 60 hz sine
wave.
I really have no idea what the RFI is that you are trying to find, and will let
others draw conclusions (I never try and guess). If it's somehow power line
RFI and you are close to the source then you should also hear it up on 136 MHz
as an example using a handheld beam turned to 136 MHz but even if it's not
power line noise you might hear it on 136 MHz. A perfect example is that last
year I had a home 0.14 miles from my QTH that had a bad LED light fixture in
the garage that was generating a lot of RFI on 160 and 80 meters and when I was
in the street in front of this home I easily heard the same RFI up on 136 MHz
and my 136 MHz DF gear pointed right at this house as did my HF DF gear.
Nowadays many things sound like power line noise so it's very confusing. I use
my family room LED light dimmer as a power line RFI generator simulator as an
example.and depending on it's setting it looks and sounds just like power line
noise arcing 1 time per each half cycle (and I hear it on HF and VHF) and it
even interferes with our reception of a weak UHF over the air digital TV
station.
Not sure if my pictures will get posted so you might add them to your folder
for others to see if they do not get posted.
Don wd8dsb
On Tue, Nov 25, 2025 at 7:16 PM Jim Brown <jim@audiosystemsgroup.com
<mailto:jim@audiosystemsgroup.com> > wrote:
On 11/25/2025 11:46 AM, Jeff (W4DD) wrote:
> I think the antenna is a StepIR vertical. It seems to have a narrow BW.
I wouldn't expect it to be narrow on receive.
I'm not familiar with Flex rigs. Elecraft has very good RX bandpass
filters on each band (or pairs of higher bands, and I would expect Flex
to do the same.
Do you hear the noise on on other bands?
73, Jim K9YC
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