RogerS wrote:Malc2098 wrote:OK.
I've got a little DAB/FM radio plugged into the circuit with it's wallwart, is that what they're called?
Play DAB with lights off - all good.
Play DAB with lights on - no interference.
Play FM with lights off - all good.
Play FM with lights on - interference.
What does that tell us, Bob?
It tells us that you're not using the right waveband ! Try MW and tune around.
I'm not sure quite what Roger is driving at with his suggestion but i will try and describe what is going on.
The home plug signal uses a wide band of frequencies from 1.8 MHz to 30MHz and to work it requires that there are not other signals in that band on the mains cable to which it is connected.
Fm radio occupies 88 to 108 MHz and DAB 175 MHz to 230MHz.
Malcs experiment shows that his lighting is producing signals of significant power at least up to 108MHz but not at high as the 175-230MHz band.
Typically the power supply modules will be switching at around 100kHz with a pulse waveform. If we do the maths (and I'm not going to) this contains odd harmonics of 100kHz ie 100, 300 700, 900kHz 1.1MHz and so on. the amplitude of each harmonic reduces very slightly from one to the next as the frequency increases.
Malc's experiment shows that those harmonics are still going strong at 1000 times the fundamental frequency of 100kHz ie up into the 100MHz region. To cause interference the power in the harmonic has to be greater than that coming from the local radio transmitter which might not be very strong say at the micro watt level (millionth of a watt).
The power unit for the lights are pulsing at 40 watts per light at 100kHz and the 1000th harmonic (well actually the 1001,1003 1005th etc harmonic) will still have power in the micro watt range and cause the interference by being stronger than the broadcast transmitter
You might need to read this a few times and apply aspirins but you should be able to follow with a bit of application.
Bob