Friday 9 April 2021

An RF-Quiet LED 'Fluorescent' Bulb




I recently had the fluorescent bulb in one section of the under-cabinet kitchen counter lighting fixture go dark. This wasn’t too surprising as the 24” bulb had been in place since the house was built in 1990!

I purchased the replacement bulb only to find out that it was not the bulb but rather the ballast transformer that had failed.

A search for a suitable ballast replacement turned into a quick education when I learned that these things were quickly disappearing, with many models no longer even being manufactured. Another solution would have to be found and it appeared that fluorescents were bring replaced with, what else ... LED fixtures!

Offering similar brightness and colors as traditional fluorescent fixtures, the LED bulbs came in two basic styles.

One type lets you just pop-in a new LED ballast-compatible bulb and away you go. This is convenient but still wastes energy in the ballast and eventually would require an even harder to find ballast.

The second type is a directly-wired LED replacement, not relying on the ballast transformer at all. Having its own built-in switching power supply, these bulbs connect directly to the 120V AC line normally going to the ballast. It’s a very simple task to snip the 120V AC leads from the faulty ballast and connect them to one end of the bulb’s socket. Now totally disconnected, the original ballast can be left in place as is.

The entire fix took less than 30 minutes ... but how much noise or crud would the switching supply produce in the RF spectrum?

Crossing my fingers, I turned the light 'on' as well as my portable Sony ICF-2010 shortwave receiver. I could hear no noise coming from the radio. I could only detect some RF hash when I put the Sony (with its built-in ferrite bar antenna) right beside the fixture! This was good news and its quiet footprint was confirmed later, out in the shack, with radios connected to much larger antennas.

The bulb I used was a ‘toggled’ product, designed and engineered in Detroit , but I suspect is manufactured, like so many other LED devices, in China. The bulbs are sold in Canada and in the U.S. by Home Depot and possibly others.

If you’re looking for a radio-friendly fluorescent replacement or update, I have no hesitation in recommending these directly-wired LED bulbs from ‘toggled’.

And, if you’re also looking for a ham-friendly light-dimmer, see my previous blog on my own hunt for a noisy next-door neighbour.


Dave said...

Some light electronics definitely can produce enough RF noise to cause problems! I recently replaced a CFL bulb in my garage door opener with a NEW OUT OF the BOX FEIT Electric LED bulb, 800Lu Soft white. The next day I noticed we were having problems getting the door to open with any of the remote openers. My first thought was - well it's time to change the batteries. Well that didn't change a thing. Good thing I am a HAM and think about things RF, others might have thought the opener electronics went bad. My next thought was what did I change? I first removed the culprit bulb and everything started working again, great. I tried several different bulbs before deciding to use an incandescent bulb from way back in the closet.

Photon said...

Interesting post. Except for outdoor LED ('security') lights, I have not seen any RFI from LED products of a fair few varieties by now. And I am very strict with the RF conditions at home; I'm a fairly serious WSPRer!

The odd thing is that we don't see articles like your post on the 'mainstream' ham press. I've asked repeatedly for a database of RFI-quiet products to be listed by national societies, etc. But this seems to be like asking for a lift to Mars by 2pm. I never understood why...

Anonymous said...

When you're looking for rf pollution from LED systems, make sure you check more than HF. You'd better look from LF-UHF. I've seen "crawlers" running through sdr waterfalls from LED replacement 60 w bulb lamps on 2200m and also LED's are notorious for VHF pollution. Like Dave did... back to incandescents... if you can still find them. I guess it's theoretically possible to find some that don't pollute from LF-UHF, but it's a crapshoot.