Hi Jeff,
1) I vaguely see what appears to be an approximate 19 KHz repeating signal
which may or may not be related to the issue at hand.
2) Can you please tell us how it was determined that the house in
question was identified as the likely source of the RFI (was radio
direction finding gear used, please describe)?
3) Can you send me an audio file with the SDR receiver in AM mode and with
the bandwidth set extremely wide (the wider the better, and 20 KHz or wider
is best). Ideally, I would like a link to the stored SDR file that
captures the RF spectrum (5 to 10 second clip). I know HDSDR stores a .wav
file that contains the RF spectrum and this is very useful for analysis
after the fact but I'm not sure what software you're using.
Thanks,
Don (wd8dsb)
On Mon, Nov 24, 2025 at 11:28 AM Jeff (W4DD) <w4dd09@gmail.com> wrote:
>
>
>
>
> 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
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>
> CAUTION: This email originated from outside of the University System. Do
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> 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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