[RFI] RFI Solved After 2 Years

[Jim Brown]

These are great observations. Some definitions are in order. In the 
world of electrical parts suppliers, the "electronic transformer" that 
is virtually universal today to run LV lighting is a Switch Mode Power 
Supply, which we all recognize as a noise generator. A REAL transformer 
feeding a rectifier/capacitor filter, with or without regulation, is 
called a "magnetic transformer."

In my limited experience, "electronic transformers" are small enough to 
fit in the backboxes for most lighting fixtures, but "magnetic 
transformers" are not. This is the problem I ran into in the home we 
bought in W6 15 years ago. My EU Beverage runs about 30 ft from that 
fixture, so the best I could do was chokes on the wiring.

A few years ago, I replaced the incandescent bulbs in those fixtures 
with LEDs from Wired Communications, a vendor who has for many years 
exhibited at West Coast ham events.

https://www.wiredco.com/LED-Lighting-Low-Voltage-s/1874.htm

A linear PSU, purchased from a mainstream industrial electronics vendor, 
is mounted in the ceiling above one of the fixtures. The greatly reduced 
current requirement of the LED instruments made it practical to fit a 
suitable PSU. I no longer need to bug the XYL to turn off the bathroom 
lights when I want to use that Beverage. I don't use a dimmer on that 
fixture.

Also in my limited experience, Lutron has historically made dimmers that 
are pretty quiet. At least 15 years ago, I had contact with one of their 
designers, talking about RFI. I've not used dimmed lighting, but serious 
TopBand DXer NI6T told me years ago that a specific Lutron model was 
quiet, and when I needed one for the room where I read, I bought a 
Lutron. Since I'm the only one who uses it, I have no idea how noisy it 
might be. :)

73, Jim K9YC

On 7/10/2020 10:14 AM, Jim McCook wrote:
> Frank,
> 
> I don't have access to the Lutron dimmer model.  The electrician simply 
> stated that it's designed for dimmable LEDs.
> 
> Perhaps you're dealing with the switching power supply for the LEDs, an 
> entirely different problem.  Do the LEDs have a separate PS or are they 
> contained within the actual light?  I have had to deal with RFI from 
> many pendant or chandelier LEDs, and even the dreaded strip LEDs, all 
> which have switching power supplies that are radiating monsters.
> 
> For pedants and chandeliers the little PS (POS) is usually in the back 
> box.  I've had luck with installing Corcom filters between the line and 
> that PS.  For tough cases or with strip LEDs you have to go to the attic 
> to install a "magnetic" PS, readily available on Amazon.  This is just 
> one example:
> 
> https://www.amazon.com/LEDwholesalers-Dimmable-Magnetic-Transformer-Flexible/dp/B00J1ZVKSQ/ref=sr_1_8?ie=UTF8&qid=1516573754&sr=8-8&keywords=magnetic+transformers+for+LED+lighting 
> 
> 
> In any of those cases the switching PS must be first discarded (smashed 
> or burned works well).  73, Jim W6YA
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