[RFI] Dimmer Behavior

Gary Johnson gwj at me.com
Fri Mar 11 12:15:46 EST 2022

I experienced exactly that oscillatory behavior when multiple LED fixtures were connected to ANY model of dimmer. The problem was induced by adding commercial EMI filters to each fixture. There was no time to investigate the exact nature of the  interaction. My guess is that the switching frequencies of each fixture were beating against one another, which appeared as low-frequency cyclical changes in line voltage. The dimmer apparently responds to that. But it’s only a guess… A Lutron dimmer was one of three brands tested and all behaved the same. Ultimately, we removed the EMI filters and replaced them with CM chokes. Everything worked properly but the RFI suppression In that case was not nearly as effective as with the EMI filters.

Here’s a detailed report on a particular Lutron dimmer: https://na6o.com/main/RFI_files/Lutron_Diva_Dimmer_Switch.pdf
I found it’s RFI generation to be unacceptable on the low bands. No way to know if other/later versions are similar without testing.

Gary NA6O  

> On Mar 11, 2022, at 7:30 AM, rfi-request at contesting.com wrote:
> From: Dan K2YWE <dan.k2ywe at gmail.com>
> To: Rfi List <RFI at contesting.com>
> Subject: [RFI] Dimmer Behavior
> I just replaced a chandelier that had 5 LED candelabra base 4-element LED
> lamps in it (the ones shaped like flames). It worked fine for years with
> our ancient Leviton dimmer (up-down buttons and little leds) using a mix of
> GE and Feit LED lamps.
> The replacement chandelier has only 4 sockets. I put in the same LED lamps
> and the dimmer just continuously cycles the lights from bright to dim. If I
> remove one of the four lamps it behaves normally. The brand of the three
> doesn't seem to matter.
> If I put in a Feit in the 4th slot it stays unlighted but the other three
> work fine. If I put a GE in the 4th slot I get the cycling behaviour. An
> incandescent 4th lamp makes everything work normally.
> Clearly the old dimmer can't handle the 4 LED loadline.
> I need a recommendation for a modern LED friendly dimmer that is known to
> be EMI-Free, I operate 160m-6m.
> 73, Dan

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