6khz BW
Agree. Normally see 60,120, 240 Hz components.
I have seen single arc on one half cycle only but it is rare. Have also
seen 5 per half cycle. The audio difference is clear with a higher pitch
on the 5 per half cycle.
Will try a capture at wide BW tomorrow.
Thanks for your input Don
On Mon, Nov 24, 2025, 9:46 PM Don Kirk <wd8dsb@gmail.com> wrote:
> Hi Jeff,
>
> What was the bandwidth setting for the audio clip? Looking at the audio
> it has heavy 60 Hz content (not 120 Hz). It has an overall repeating
> pattern at a frequency of 60 Hz. When dealing with power line noise I
> typically see spikes at a frequency of 120 Hz (arcing at least once time
> during each half cycle of the sine wave). I know some power line arcing
> can happen during just one half of the sinewave but I've never encountered
> that situation. If the bandwidth of your AM audio recording was less than
> 20 KHz, can you post another audio clip using a bandwidth of at least 20
> KHz (I prefer 25 KHz)?
>
> Thanks,
> Don wd8dsb
>
> On Mon, Nov 24, 2025 at 8:46 PM Jeff (W4DD) <w4dd09@gmail.com> wrote:
>
>>
>>
>> I posted some additional pictures of the noise and an audio clip to the
>> link
>> below.
>>
>>
>>
>>
>>
>>
>>
>> From: Jeff (W4DD) <w4dd09@gmail.com>
>> Sent: Monday, November 24, 2025 11:17 AM
>> To: 'rfi@contesting.com' <rfi@contesting.com>
>> Subject: FW: [RFI] RFI Signature
>>
>>
>>
>>
>>
>>
>>
>> Thanks to all that replied. Some interesting thoughts to consider. I
>> had a
>> couple of Laughs also since several experts mentioned things I had been
>> thinking. I had pulled out a lawn tool battery charger (K9MA) and
>> experimented with that. It did produce a similar spectrum display, but I
>> still can't account for why the source would be mostly at power level 2 or
>> 3. Seems like the battery would eventually be charge and it would drop to
>> level 4, which we seldom see. My battery was fully charged and the noise
>> level was very low.
>>
>>
>>
>> A demand driven device (K8CN), seems logical. It is not related to wx and
>> does not change based on outdoor temperature so likely not HVAC. POE is
>> an
>> interesting idea I had not considered.
>>
>>
>>
>> A ckt brkr based sniffer (WD8DSB). I actually built one of those (thanks
>> Don). Unfortunately, the neighbor is resistant to anyone entering the
>> home.
>> This is also a remote assist, so I don't get to actually visit the site.
>>
>>
>>
>>
>>
>>
>>
>> For those that asked, here is a waterfall capture. Noise at the -71/-72
>> level (level 2 of 4 levels).
>>
>> Antenna is a multiband vertical, tuned to 3540KHz.
>>
>>
>>
>>
>>
>>
>> https://drive.google.com/drive/folders/1jYH07St1bSd0-Coqhl76HhraKbdYX2e-?usp
>> =drive_link
>> <https://drive.google.com/drive/folders/1jYH07St1bSd0-Coqhl76HhraKbdYX2e-?usp=drive_link>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> _____
>>
>> From: RFI < <mailto:rfi-bounces+mike.carter=unh.edu@contesting.com>
>> rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf of Jeff (W4DD)
>> <
>> <mailto:w4dd09@gmail.com> w4dd09@gmail.com>
>> Sent: Sunday, November 23, 2025 2:10 PM
>> To: <mailto:rfi@contesting.com> rfi@contesting.com <
>> <mailto:rfi@contesting.com> rfi@contesting.com>
>> Subject: [RFI] RFI Signature
>>
>>
>>
>> [You don't often get email from <mailto:w4dd09@gmail.com>
>> w4dd09@gmail.com.
>> Learn why this is important at
>> <https://aka.ms/LearnAboutSenderIdentification>
>> https://aka.ms/LearnAboutSenderIdentification ]
>>
>> CAUTION: This email originated from outside of the University System. Do
>> not
>> click links or open attachments unless you recognize the sender and know
>> the
>> content is safe.
>>
>>
>> I am working on a RFI case that we believe is coming from a nearby home.
>> The owner is a little cooperative, but is not interested in doing a ckt
>> breaker test. The noise exhibits some interesting characteristics that
>> may
>> help us in suggesting he unplug a device. Perhaps someone has seen this
>> before.
>>
>>
>>
>>
>>
>> 1. On the pan adapter, looks like power line noise. Random dots
>> across
>> the screen.
>> 2. No repeating clusters of noise vs frequency that might suggest a
>> SMPS.
>> 3. No correlation to sunlight or darkness. No correlation to time of
>> day.
>> 4. Has distinct levels of interference; we have noted -85dBm, -78dBm,
>> -72dBm (S-9), -66dBm. Interesting the levels are about 6dB apart. -78
>> and
>> -72 are most common.
>> 5. The neighbor has a solar system installed roughly 2 years ago, but
>> as mentioned, no correlation to sunlight/darkness or time of day.
>> 6. Affects mostly 80M but can be heard on other bands
>>
>>
>>
>> Has anyone seen 4 levels of noise from a device before?
>>
>>
>>
>> Thanks for any ideas.
>>
>>
>>
>>
>>
>> Jeff, W4DD
>>
>>
>>
>>
>>
>>
>>
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