Re: Valve amplifier picking up EMI/RFI
Some time ago I had a lot of noise when listening to FM. I had a hard time figuring out what it could be, since it only appeared sometimes, and always in the evening. The noise made it impossible to use the FM band, especially on the lower frequencies. I was sure it was a charger or the internet router, but disconnecting them made no difference.
It turned out to be a light bulb. Not an LED type, but the one shown in the picture. They are probably cheap production ones, as the supports for the filament tends to loosen after some time of use, and when watching the filament carefully, it actually vibrates a little, probably from the mains frequency.
Where the filament strings are very close to each other, I believe they make contact and creating some kind of spark which is not visible to the eye, but certainly audible when listening to FM. Never had I ever suspected a light bulb to be such an effective noise transmitter. Nowhere in the house was it possible to use the FM band when light was on in the kitchen.
Jan
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