[RFI] Noisy LED shop lights

[Dale Johnson]

Jim,

I bravely opened up one of these light just out of curiousity.  There is a green wire connection to the board and also it’s run to the metal of the light fixture.  I didn’t go any more deeper into it as it would be unsoldering wiring which I didn’t want to do.  The board has many components.  I am wondering if it’s radiating directly or it’s using the power wiring as antenna.  I should try one of my large ferrites and loop several turns though one and see if there’s a change, I’m skeptical though.  

Dale, K9VUJ


On 13, Jun 2018, at 18:22, Jim Brown <jim at audiosystemsgroup.com> wrote:

On 6/13/2018 12:48 PM, Stephanie WX3K via RFI wrote:
> Here is a helpful link
> https://www.digikey.se/Web%20Export/Supplier%20Content/Lambda_285/PDF/TDKLambda_all_about_emi_epmag.pdf
> 
> If you search Amazon by entering EMI filter you will find a variety for different applications.

BUT THE LINK IS WRONG! It is the EMC compliance tech's view of the world.

These filters work ONLY if properly mounted and built INTO equipment. In general, they do NOT work for most real world problems that put noise on the power line as current on the green wire.

The most common cause of noise coupling to and from power and signal wiring is that the green wire, or the cable shield, fails to contact the shielding enclosure at the point of entry/exit. This puts noise current on the green wire of the cable shield, and it causes noise current on the cable shield to enter equipment. Neil Muncy, ex-W3WJE (SK), first exposed this in 1994, and a fellow member of the AES Standards Committee Working Group on EMC named it "The Pin One Problem." See my website for a lot of tutorial material on this.

The only fix for this (without modifying equipment) is a ferrite common mode choke. And simply clamping a few onto the cable does NOT WORK at HF. Those clamp-ons are designed for VHF noise. Study

k9yc.com/RFI-Ham.pdf  and

http://k9yc.com/KillingReceiveNoise.pdf

73, Jim K9YC

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