A brief look at Generac's PWRcell system description
alludes to configuring sub-arrays of PV modules around
a '2500 watt optimizer,' a central inverter, and a Li-ion battery
bank. No doubt the optimizer is a DC-DC switch mode converter,
and the Li-ion battery charger may be another source of
RFI. There can be multiple optimizers for an array comprising
several sub-arrays.
Glad to know that W9RE's neighbor benefited from
Generac's mitigation of RFI as well as Mike's quieting
of the affected bands. It is good to know that W1EMI
has the right contacts at Generac to effect the resolution
of RFI problems.
73,
Mike, K8CN
________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf of Don
Kirk <wd8dsb@gmail.com>
Sent: Thursday, August 1, 2024 5:08 PM
To: K9MA <k9ma@sdellington.us>
Cc: rfi@contesting.com <rfi@contesting.com>
Subject: Re: [RFI] New RFI Source
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.
Hi Scott,
Yep, it was a Generac system in our case at W9RE last year, and you
definitely need to work with Steve at the ARRL as he has great contacts
within Generac which greatly helped us. I prefer not to get into the
details online regarding our resolution but it was almost too good to be
true (the homeowner benefited greatly).
I’ll e-mail you my phone number and I’ll fill you in on the details.
Don wd8dsb
On Thu, Aug 1, 2024 at 3:57 PM K9MA <k9ma@sdellington.us> wrote:
> Source found. It's a Generac solar system 640 meters (0.4 miles) from my
> tower. The homeowners were very cooperative, and switched the inverter
> off for the test, which was conclusive. The location is almost exactly
> on my 20m beam heading.
>
> It's a partly cloudy day here, so I suspect the variations in the signal
> I'm seeing were due to solar power fluctuations.
>
> I'll try to get the installer and Generac to fix the problem. Has anyone
> had any experience with Generac?
>
> 73,
> Scott K9MA
>
>
>
>
> On 8/1/2024 1:04 PM, K9MA wrote:
> > Hi Mike,
> >
> > The other copies (harmonics of 78 kHz) show exactly the same
> > structure. I hear the signal only on 20 meters, across the whole
> > band. They certainly go beyond the band, but it's hard to tell how
> > far due to antenna bandwidth. Looking at the whole band, I'm actually
> > seeing harmonics of 39 kHz, though the 78 kHz harmonics are stronger.
> >
> > Looks like I'll be taking a walk this afternoon.
> >
> > 73,
> > Scott K9MA
> >
> > On 7/31/2024 7:26 PM, Michael Carter wrote:
> >> Scott, do the spectral copies at 78 kHz intervals
> >> mimic the sideband structure shown in your K4
> >> screen capture?
> >>
> >> Over what frequency range can you see the
> >> spectral copies (limited by antenna bandwidth,
> >> I suppose)?
> >>
> >> The120 Hz spaced fine spectral lines in the
> >> main lobe suggest to me a 120 Hz square
> >> wave modulating an underlying 'carrier' signal.
> >> AC power line signal rectified
> >> in the power supply for the device and coupled
> >> into the 'clock' carrier and its harmonics?
> >>
> >> The more distant sidebands don't exhibit the
> >> fine 120 Hz structure of the main lobe. That's
> >> what's puzzling me.
> >>
> >> I'll be very interested to see what your DF'ing
> >> leads to......
> >>
> >> 73,
> >> Mike, K8CN
> >> ------------------------------------------------------------------------
> >> *From:* K9MA <k9ma@sdellington.us>
> >> *Sent:* Wednesday, July 31, 2024 5:56 PM
> >> *To:* Michael Carter <Mike.Carter@unh.edu>; rfi@contesting.com
> >> <rfi@contesting.com>
> >> *Subject:* Re: [RFI] New RFI Source
> >> 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.
> >>
> >> The carriers within that main lobe appear to be 120 Hz apart, so
> >> likely line related. They seem to vary in amplitude, but are very
> >> stable in frequency.
> >>
> >> 73,
> >> Scott K9MA
> >>
> >>
> >> On 7/31/2024 4:28 PM, Michael Carter wrote:
> >>> Hi Scott,
> >>>
> >>> The sidebands are not typical of any SMPS I've
> >>> looked at spectrally. The fine spectral structure
> >>> inside the main lobe suggest 60 Hz or 120 Hz
> >>> modulation of the nominal 'carrier', but the
> >>> sideband spacing of ~ 1 kHz from the main lobe
> >>> is odd.
> >>>
> >>> What do you see when you zoom into the
> >>> main lobe? Can you guesstimate the
> >>> spacing of the strongest sidelobes
> >>> within that lump?
> >>>
> >>> 73,
> >>> Mike, K8CN
> >>>
> ------------------------------------------------------------------------
> >>>
> >>> *From:* RFI <rfi-bounces+mike.carter=unh.edu@contesting.com>
> >>> <mailto:rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf of
> >>> K9MA <k9ma@sdellington.us> <mailto:k9ma@sdellington.us>
> >>> *Sent:* Wednesday, July 31, 2024 5:08 PM
> >>> *To:* rfi@contesting.com <mailto:rfi@contesting.com>
> >>> <rfi@contesting.com> <mailto:rfi@contesting.com>
> >>> *Subject:* [RFI] New RFI Source
> >>> 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.
> >>>
> >>>
> >>> This RFI source has appeared recently:
> >>>
> >>>
> https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsdellington.us%2Fhr%2FRFI%2F24.07.31.png&data=05%7C02%7Cmike.carter%40unh.edu%7Ce06cf52f2142423f715308dcb26e39e5%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638581433706160002%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=9fOgQrmq5iBd8KNa4n3pFex7BNvLNtAUeVadP80%2FNyw%3D&reserved=0<https://sdellington.us/hr/RFI/24.07.31.png>
> >>> <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsdellington.us%2Fhr%2FRFI%2F24.07.31.png&data=05%7C02%7Cmike.carter%40unh.edu%7Ce06cf52f2142423f715308dcb26e39e5%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638581433706173580%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=zS2Tdd88IPUDgkP9lOr5FuwJ8qV2d6xFLoj4JmLih4U%3D&reserved=0<https://sdellington.us/hr/RFI/24.07.31.png>>
> >>>
> >>> It appears to be harmonics of about 78 kHz. However, unlike most SMPS
> >>> RFI, it is very stable. It disappears at night, suggesting a solar
> >>> system, but it persists, weakly, an hour or so after sunset. Maybe a
> >>> solar system comm link, with a supercapacitor? However, I'm not
> >>> aware of
> >>> any new solar systems nearby. Anyone seen anything like this before?
> >>>
> >>> Needless to say, I'll be out tracking it soon.
> >>>
> >>> 73,
> >>>
> >>> --
> >>> Scott K9MA
> >>>
> >>> k9ma@sdellington.us <mailto:k9ma@sdellington.us>
> >>> _______________________________________________
> >>> RFI mailing list
> >>> RFI@contesting.com <mailto:RFI@contesting.com>
> >>>
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> >>> <https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.contesting.com%2Fmailman%2Flistinfo%2Frfi&data=05%7C02%7Cmike.carter%40unh.edu%7Ce06cf52f2142423f715308dcb26e39e5%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C638581433706186898%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=5MEGCedNwTYgquzfPeis0fPjOWbk7WGryxFMmMTF6W4%3D&reserved=0<http://lists.contesting.com/mailman/listinfo/rfi>>
> >>
> >>
> >> --
> >> Scott K9MA
> >>
> >> k9ma@sdellington.us <mailto:k9ma@sdellington.us>
> >
> >
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
> _______________________________________________
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