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LED Bulbs and RFI – My First Experience

LED Bulbs
Governments everywhere are pushing adoption of LED bulbs. Great idea, but will they cause radio frequency interference? Let’s find out. 

Traditional incandescent lights were never designed for efficiency. Quite the opposite, actually. Thomas Edison experimented with thousands of materials before he came up with slow-burning bamboo filaments. Later, tungsten took over. Our old incandescent bulbs used 90% of their energy on heat. Incidentally, this isn’t a bad idea in cold Calgary winters. In recent years, most of us have switched to more efficient compact fluorescent bulbs, which use around 75% less electricity.

Now governments are pushing LED bulbs. In 2017, the Government of Alberta started offering massive subsidies which reduced the cost of many LED types down to a dollar. So, I bought some A19 and BR30 LED replacements. Two of the 60 watt equivalent bulbs have gone into my radio room, and six of the 75 watt equivalents onto the main floor just above.

I am please to report that I cannot detect any radio frequency interference from the LED bulbs. According to this research report from ARRL, if you stick to brand names and stay away from dimmers, you should be relatively free of RFI. Also, my advice is to only use drop-in replacement bulbs and stay away from external ballasts.

LED Bulbs – How They Work

My only concern with LED bulbs is that they contain switched mode power supplies in their base. SMPS are notorious for creating radio interference. In the base of the LED lamp, a SMPS converts 120 VAC down to low voltage DC. The main cause of RFI from SMPS is poor design, poor filtering and voltage-drop induced radiation in the wiring between the power supply and the device. These LED bulbs that I installed do not seem to suffer from any of these challenges.

If you are interested in the electronics involved, check out these reference LED light designs from Texas Instruments.

You might be surprised to learn that LED bulbs are not that much more efficient than CFL bulbs. Their advantage lies in two things. First, longer life. They should last as much as 2-5 times as long as CFL. Second, the light is focused rather than isotropic. LED lamps contain as many as 100 or more little LED diodes that can be arranged to provide light in the most useful directions.

If the 22 year lifetime claim proves valid, changing light bulbs may become a thing of the past.

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