Sparking on the positive half of the cycle occurs when the sparking is going
from a appointed object to a flat surface. It creates partial rectification.
The multiple discharges per half cycle are created by the size of the gap. A
smaller gap would give multiple discharges in a larger gap would give fewer
discharges. Typically those gap sizes and the number of discharges perhaps
cycle will change from morning to later in the day with temperature and
moisture levels. As humidity occurs or dissipates it changes the wood on the
poles with a hardware is and has the wood swells up or shrinks up it changes
the size of the gap and the hardware that sparking.
The multiple discharges typically create a higher pitch sound because they're
occurring repetitively very fast. The slower discharge of the larger gap
usually sounds a little lower in tone frequency.
Mike Martin
RFI Services
240-508-3760
51 W Bay Front Rd
Lothian, MD 20711
rfiservices.com
________________________________
From: RFI <rfi-bounces+mike=rfiservices.com@contesting.com> on behalf of Jeff
(W4DD) <w4dd09@gmail.com>
Sent: Monday, November 24, 2025 10:02:02 PM
To: Don Kirk <wd8dsb@gmail.com>
Cc: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] RFI Signature
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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