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Steve Taranovich

Christmas lights and other RFI---Bah humbug

Steve Taranovich
Victor Lorenzo
Victor Lorenzo
12/25/2015 3:57:52 AM
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Blogger
EMI from simple circuits
Switched mode power suppliers are often at the heart of our EMI and RFI issues during certification, but other simple devices and circuits also create a lot of wideband RFI.

I worked on a circuit where the conmutation of one small relay at the same time of a few LEDs produced a wideband perturbation in the VCC lines. This perturbation was coupled to a pair of external cables and produced RFI in all bands from 30MHz to 2.5GHz with peaks spaced only a few MHz.

Incandescent bulb christmas lights are still out there, some of them produce a lot RFI when dimming, at some times enough RFI to interfere with the TV nearby the christmas tree.

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steve.taranovich
steve.taranovich
12/25/2015 12:27:16 PM
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Blogger
Re: EMI from simple circuits
Hi Victor,

Thanks for sharing your experiences with our readers

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richmarkley
richmarkley
1/7/2019 8:04:37 PM
User Rank
Newbie
Hunting pesky LED interference

The whole topic is interesting as we transition to all LED lighting, eventually. I still prefer the warmth of incandescents, tbough LEDs are getting better. Or, maybe I am just getting used to them and starting to like not having to change 20 bulbs every year (or throw out a full set of lights again, like I did this Christmas).

To detect EMI, grab a handheld spectrum analyzer (I'm with R&S so I naturally have an affinity toward R&S equipment, such as the Spectrum Rider ZPH.

Connect a directional antenna and you can quickly find the offending string of lights. And since it can measure signals up to 4 GHz, you can see if your lights—or those of your neighbors—are really slowing down your Wi-Fi:)

Fun application of a useful tool: Thanks Steve. 

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