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[RFI] Finally located my RFI

To: rfi@contesting.com
Subject: [RFI] Finally located my RFI
From: "Dave (NK7Z)" <dave@nk7z.net>
Date: Wed, 19 Jun 2024 17:50:24 -0700
List-post: <mailto:rfi@contesting.com>
Howdy,

I have been chasing an RFI source that comes on and goes off on about a 7 minute cycle for 3 months now, I have suspected it was HVAC related by it's behavior... and timings of changes I have seen... Runs different at night, if an abrupt temp change occurs, a corresponding change in the cycle times, and lengths...

It consists of broadband noise from 17 MHz, to 29 MHz. Worst at 24 MHz, not bad on 28 and 17 Mhz. It did not do this when it was installed, it has recently changed... He has had a lot of electrical work of late as well.

Anyway, my neighbor had his vents cleaned, and let me know in advance... I started my S Meter logger last night, and ran it all night, and this morning... Seven Minutes after the HVAC people arrived, the RFI ended... I asked the tech about this, and he said he had just shut off the units... BINGO!!!!!!!!!!!!!!!! I asked him to text me as he brought up each unit... He did, and I now know what unit it is causing the issue...

He also indicated they were having issues with the Mitsubishi inverter unit getting into people's LED lights, and cycling them... Sounds like it is really noisy on the power grid...

Does anyone have any experience or a contact at Mitsubishi, or any suggestions on mitigation of this? I may start by having the HVAC people install some ferrites on the power to the inverter, at the inverter... But I want to contact Mitsubishi as well and see if they have an RFI kit...

The unit model is SUZ-KA12NA, Service Ref: SUZ-KA12NAR1.TH

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

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