24 Nov
2011
24 Nov
'11
1:02 p.m.
Eventually a electrician figured out the LED bulb was
causing enough
radio interference to disrupt the remote control receiver.
However, I seem to remembner reading that old filament bulbs can cause TF
interference too. Some valve radios over here used a low-powered ligth
bulb as the dropping resisotr in the series heater chain [1] and when
the bulb got old, yuo'd get interference on the output.
Nothing to do with an intermitany break in the filament, IIRC the effect
was somethign to do with the evapourated metal from the filament on the
inside of the glass (which is why it only occured with old, blackened
bulbs) collecting electrons from the filament. But there was more to it
than that. I will see if I can find the articles.
For some reason the term 'Barkhausen effect' is coming to mind. But that
may be a collision ib my hash tables.
[1] One UK magazine actually published a design for a combined radio and
table lamp (!).. Yes, the lamp bulb was the heater dropper resistor.
-tony