[RFI] Fw: Question for the group...

[Michael Carter]

Another reply sent directly to the poster NK7Z, which I forgot to include to the list!

Resolution for 2025:  check the outbound email list carefully before hitting send!

73,
Mike, K8CN
________________________________
From: Michael Carter <Mike.Carter at unh.edu>
Sent: Wednesday, December 31, 2025 9:53 PM
To: Dave (NK7Z) <dave at nk7z.net>
Subject: Re: [RFI] Question for the group...

Hi Dave,

The microinverters, DC optimizers, and central inverters are required to meet FCC Part 15, Class B requirements. The PV modules themselves, unless they directly incorporate one of the aforementioned power converters, do not fall under Part 15. Unfortunately, the Class B limits do NOT include radiated emissions below 30 MHz.  The limits do include ** conducted ** emissions into the AC line below 30 MHz.  There are limits on radiated emissions, but only above 30 MHz.  Class B residential devices are considered unintentional radiators if their primary purpose is not communication.

Most radiated emissions in a PV system stem from the inter-module wiring between microinverters or DC optimizers and the central inverter of an optimizer-based design.  Since the microinverters connect in parallel directly to the AC grid, and the wiring on the DC side to the PV module is short by comparison, the Part 15 limits on conducted emissions into the AC grid are effective in reducing radiated emissions.  A system using DC optimizers arranged in series strings is more prone to radiated emissions because of the typical lengths of interconnecting cables.  Since the series strings are connected at a central inverter, the limits on conducted emissions into the AC grid are not as helpful since the RFI from DC optimizers (DC/DC converters) is free to be radiated by the interconnecting cabling.

See CFR 47: https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15/subpart-B

73, and Happy New Year,
Mike, K8CN


________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu at contesting.com> on behalf of Dave (NK7Z) <dave at nk7z.net>
Sent: Wednesday, December 31, 2025 9:13 PM
To: RFI Mail list at contesting.com <rfi at contesting.com>
Subject: [RFI] Question for the group...

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 have a neighbor getting ready to install Solar, he lives about 600 to
1000 feet from my home.  He is very cooperative, and had contacted the
vendor.  I will be running tests prior to turn on.

I want to insure I have my ducks in a row for this, in the event it
turns sour.  I will run a spectrogram from 3-30 MHz, via my SDR to get a
baseline before the Solar system goes live.

Just to be sure, solar does fall under part 15?  Is that correct?

73, and thanks,
Dave (NK7Z)
https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.nk7z.net%2F&data=05%7C02%7Cmike.carter%40unh.edu%7C0930c60e9cb8476e464c08de48db7245%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C639028304523073961%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=JEHHUDNfJWNKTiMigkIahu7nfxzVUfNjyEwlD1xT6Jg%3D&reserved=0<https://www.nk7z.net/>
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

Random Quote of the day:
What did one charged atom say to the other? I got my ion you



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