Monday, 26 October 2015

kitchen LEDs run interference on DAB radio shock

One of the kitchen refit changes was to replace the previous halogen ceiling lights with LED downlighters.

There was an unexpected side effect. The DAB radio stopped working. Switch on the LEDs and immediately the DAB radio reception fades.

Initially I thought it could be a specific wiring or transformer problem but then I dialled it up on a couple of consumer forums and yes, it is a common problem.

It's yet another thing they don't tell you about the so-called progressive technology of DAB. The switched power supplies required to run the 12 volt LEDs can create large amounts of interference in the same radio frequency spectrum that DAB uses to broadcast.

Curiously, it seems to be mainly kitchen refits that feature in the questions about this. I guess it is because of the number of people that use stand-alone kitchen radios with very basic aerials.
PA250010.jpg - The kitchen LED downlights are making the DAB radio fuzzy
Caption: The kitchen lights are making the radio fuzzy

Next I stumbled upon the the CE test called EN55022, Class B (domestic usage) which is supposed to test that lights won't create more than a set level of interference in the 30MHz-1GHz range. That's across plenty of radio spectrum, including the 210MHz-300MHz range used in DAB broadcasting.

Guess what?

Halogen lights attain good results well below the interference levels. Swap in low-voltage LEDs and both generic and famous name brand LEDs coupled to their transformers can operate above the interference threshold at certain frequencies, particularly in the DAB range.

To figure out our situation I'd tried three different DAB radios from an inexpensive Goodmans, a mid-range Pure and an expensive Roberts. All turned into clucking chickens when the lights were switched on.

Some of the forum folk had been using trial and error to swap out (expensive) LED bulbs or (even more expensive) transformers, often without fixing the situation. In our case I'll plug in an external aerial, but it's not the solution for everyone because sometimes they don't have a nearby aerial socket for their radio.

It also defeats the object of a simple, portable radio that can operate digitally.

Another yellow card for DAB because it is so sensitive to this type of interference. Add that to the low bit-rate often used in DAB broadcasts and we have a technology that is only borderline fit-for-purpose.

Except when The Archers comes on.

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