[RFI] Dancing Carriers

Tue Dec 20 08:13:46 EST 2022

Hi,

I have a couple of RFI movies, showing a grow light startup, and 
operation, on 40, and 30 meters, across a 24 hour period located at:

https://www.nk7z.net/rfi-site-survey-part-ii-interpretation/

Scroll down a ways and you will find two movies showing the grow light 
RFI.

You can see most of what Ed is talking about with regards to startup 
drift, and on the 30 meter movie, you can see what I think was a power 
interruption about half way through.

The movies covers the entire 40, and 30 meter bands, and 24 hours of 
time.  Click the little square in the lower right corner to make it full 
screen.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 12/20/22 04:24, Hare, Ed, W1RFI wrote:
> Switchers generally exhibit a few characteristics:
> 
> o  They are generally somewhat unstable, with their free-running frequencies changing with temperature, load and supply voltage.
> o They typically generate buzzy carriers ever N kHz, with N being the free-running frequency
> o With that, they generally drift up or down when they are first turned on.
> o They usually exhibit short-term frequency variation when there is a momentary power fluctuation
> o They usually have a noticeable to very strong 60- or 120-Hz component (50- or 100-Hz in some countries).
> 
> It seems natural to ask, "What is it?,"  when looking for a device, but for many reasons, that is often the wrong question.
> 
> See this article I wrote to explain why:
> 
> http://www.arrl.org/files/file/RFI/WHAT%20IS%20IT.pdf
> 
> 
> WHAT IS IT? By Ed Hare, W1RFI - American Radio Relay League<http://www.arrl.org/files/file/RFI/WHAT%20IS%20IT.pdf>
> always drift. Stay parked on the frequency for a while, and keep listening. Switchers almost always exhibit little changes in frequency as voltage dips and surges occur,
> www.arrl.org
> 
> ________________________________
> From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of alex at kr1st.com <alex at kr1st.com>
> Sent: Monday, December 19, 2022 10:00 PM
> To: rfi at contesting.com <rfi at contesting.com>
> Subject: Re: [RFI] Dancing Carriers
> 
> Thanks everyone for taking an interest!
> 
> 
> 
> I know what a SMPS sounds and looks like. In fact, I have one in the shack
> that I can hear if I take the common mode chokes off it. It will wander up
> and down the bottom portion of 2 meters, where most of my interest is on
> that band.
> 
> 
> 
> The carriers in the video sound just like that, carriers. There is no
> detectable modulation on them. They just like a tone with no noise
> whatsoever. I will make a recording of this.
> 
> 
> 
> At this time carriers have morphed into signals like that of a stuck keyer:
> 
> 
> 
> https://youtu.be/3o_cBp_YfpQ
> 
> 
> 
> The signals are 175 kHz apart. If I zoom in on one of those carries on 6m I
> see there are two pulses. A second one is present at half the frequency
> interval 50 Hz than the first pulse:
> 
> 
> 
> https://youtu.be/asuJHFRXBxQ
> 
> 
> 
> I'm starting to think it's some sort of sensing circuit causing this. I've
> seen something similar to this latest recording many years ago when I lived
> in SC. I noticed a similar signal that was caused by the sensing circuit of
> an electric blanket a neighbor just purchased. The power supply would
> continuously send pulses through the wiring of the blanket in order to
> detect if a person was present. If it detected a person it would turn on the
> power supply. I forgot what happened to the signal when the power supply
> turned on. I wonder if I have a recording from back then (15 or so years
> ago). I seem to remember it was on 10 meters, but maybe it was 2 meters
> also. That signal was way more invasive though and made the band pretty much
> unusable. Now the lady using it had cancer and the blanket offered pain
> relief, so I wasn't going to suggest not to use the blanket of course. She
> did contact the manufacturer on her own accord, however, and got a new power
> supply that solved the problem.
> 
> 
> 
> The signal does seem to come from the direction of a neighbor's house, but
> my 10 element 222 beam indicates a 30 degree different heading than the 9
> element 2m beam. I will see if I can find some correlation with time of day,
> etc. I'm fixing my mobile installation and will drive around and see what I
> find.
> 
> 
> 
> Thanks for your help and suggestions!
> 
> 
> 
> 73,
> 
> --Alex KR1ST
> 
> 
> 
> From: Michael Carter <Mike.Carter at unh.edu>
> Sent: Monday, December 19, 2022 8:18 PM
> To: rfi at contesting.com
> Cc: alex at kr1st.com; k1ttt at arrl.net
> Subject: Re: [RFI] Dancing Carriers
> 
> 
> 
> Agreed, David (K1TTT) - the step frequency variation could
> 
> readily be due to the FFT computation interval while the
> 
> frequency wobble of the spectral lines occurs continuously
> 
> because of drift in the source.
> 
> 
> 
> Given that Alex hears this set of roughly uniformly spaced
> 
> 'carriers' on 50 MHz, 144 MHz, and 220 MHz, one would
> 
> expect that direct harmonics of any switch-mode electronics
> 
> with a fundamental switching frequency around 100 kHz
> 
> would have fallen off in amplitude long before reaching VHF.
> 
> How is this line spectrum appearing in multiple widely
> 
> spaced bands?
> 
> 
> 
> The RSP2Pro presumably generates I/Q samples after
> 
> digital down-conversion at a clock rate sufficient for the
> 
> frequency span being monitored.  I was wondering if
> 
> the I/Q data is directly tainted by switch-mode converter noise
> 
> and thus appears present in multiple VHF bands?  However, Alex
> 
> reported hearing the same noise and seeing similar 2 meter
> 
> spectra on his IC-9700, which conflicts with that hypothesis.
> 
> 
> 
> Still a fun puzzle, and I second Jim's (K9YC) request for audio samples of
> 
> the band around one or more of those wobbly spectral lines.
> 
> 
> 
> 73,
> 
> Mike, K8CN
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>    _____
> 
> From: RFI <rfi-bounces+mike.carter=unh.edu at contesting.com
> <mailto:rfi-bounces+mike.carter=unh.edu at contesting.com> > on behalf of
> k1ttt.dave at gmail.com <mailto:k1ttt.dave at gmail.com>  <k1ttt.dave at gmail.com
> <mailto:k1ttt.dave at gmail.com> >
> Sent: Monday, December 19, 2022 4:04 PM
> To: alex at kr1st.com <mailto:alex at kr1st.com>  <alex at kr1st.com
> <mailto:alex at kr1st.com> >; rfi at contesting.com <mailto:rfi at contesting.com>
> <rfi at contesting.com <mailto:rfi at contesting.com> >
> Subject: Re: [RFI] Dancing Carriers
> 
> 
> 
> 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.
> 
> 
> Signals like that which move up and down are generally something like
> harmonics of switching power supply or variable speed motor or some other
> non locked frequency digital system, that is, something that doesn't rely on
> a specific clock frequency like computers, tv's, modems, ethernet, etc
> require.  Power supplies drift with temperature, line voltage, or load.  The
> step functions you see may be because the sdr only processes the spectrum a
> few times a second so they appear to stay the same for a short time then
> jump a bit as the next set of samples is plotted and the signal has moved
> into the next fft column range.
> 
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web:
> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwiki.k1ttt.
> net%2F
> <https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwiki.k1ttt
> .net%2F&data=05%7C01%7Cmike.carter%40unh.edu%7C515021a1b3e540655d0908dae204b
> 948%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638070807160922056%7CUnknow
> n%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6
> Mn0%3D%7C3000%7C%7C%7C&sdata=5nVF1RrFflx5uKhmVAC3dEa6XHoXH2dZnJ55tdAKV3E%3D&
> reserved=0>
> &data=05%7C01%7Cmike.carter%40unh.edu%7C515021a1b3e540655d0908dae204b948%7Cd
> 6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638070807160922056%7CUnknown%7CTWF
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> d=0
> AR-Cluster node: telnet://k1ttt.net:7373
> 
> 
> -----Original Message-----
> From: RFI <rfi-bounces+k1ttt=arrl.net at contesting.com
> <mailto:rfi-bounces+k1ttt=arrl.net at contesting.com> > On Behalf Of
> alex at kr1st.com <mailto:alex at kr1st.com>
> Sent: Monday, December 19, 2022 14:57
> To: rfi at contesting.com <mailto:rfi at contesting.com>
> Subject: [RFI] Dancing Carriers
> 
> Hi there,
> 
> 
> 
> I'm trying to figure out what is generating these "dancing carriers" on 2m:
> 
> 
> 
> https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2
> FgKA0P2c-034
> <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%
> 2FgKA0P2c-034&data=05%7C01%7Cmike.carter%40unh.edu%7C515021a1b3e540655d0908d
> ae204b948%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638070807160922056%7C
> Unknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLC
> JXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Qb4CnEM%2F%2BEqJdbCL2ews866Bf6YL3zMyk99uU
> 1i5O0Q%3D&reserved=0>
> &data=05%7C01%7Cmike.carter%40unh.edu%7C515021a1b3e540655d0908dae204b948%7Cd
> 6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638070807160922056%7CUnknown%7CTWF
> pbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
> 7C3000%7C%7C%7C&sdata=Qb4CnEM%2F%2BEqJdbCL2ews866Bf6YL3zMyk99uU1i5O0Q%3D&res
> erved=0
> 
> 
> 
> I see them om on 6m and 1.25m as well. Has anyone come across this before
> and can share a hint at what may be causing this? Since the signature looks
> to be easily recognizable to someone who ran across this before I thought
> I'd ask on this list.
> 
> 
> 
> I recorded this a few minutes ago using a RSP2Pro using SDR Console and a
> CX-333 antenna at just 20ft or so. I have the gain on the RSP2 very low as
> to rule out any overloading. The beacon you are hearing is W3CCX/b on
> 144.300 MHz. The carriers are not modulated and are there 24/7. They are
> 118.5 kHz apart. I also see it on the IC-9700 with a DCI-146-4H bandpass
> filter so I don't think it's some mixing product caused by a strong out of
> band signal.
> 
> 
> 
> 73,
> 
> --Alex KR1ST
> 
> 
> 
> 
> 
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