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Andrew2 · 26th Mar 2020, 9:55 am

Hi Mike. I think you need to go down in frequency to get to the fundamentals, which will almost certainly be switch-mode power supplies running in the range 30 to 120 kHz.
In my experience, this type of noise tends not to radiate directly from the offending gadget, but creeps out onto the mains connection and into the house wiring and out into the wider world where it uses the mains cables to radiate.

I've found that harmonics (especially the higher ones) can seem to come from a different direction than the lower ones as the mains wiring has a filtering effect and distorts the radiation pattern.
You also run the risk of confusing one noise with another as they all tend to have the same buzzy sound.

I don't know what others think, but I reckon you'll get a very confused picture if you work on anything but the fundamental and maybe the low harmonics.

26th Mar 2020, 9:55 am	#2
Andrew2 Nonode Join Date: Mar 2010 Location: Dukinfield, Cheshire, UK. Posts: 2,037	Re: Radio Direction finder Hi Mike. I think you need to go down in frequency to get to the fundamentals, which will almost certainly be switch-mode power supplies running in the range 30 to 120 kHz. In my experience, this type of noise tends not to radiate directly from the offending gadget, but creeps out onto the mains connection and into the house wiring and out into the wider world where it uses the mains cables to radiate. I've found that harmonics (especially the higher ones) can seem to come from a different direction than the lower ones as the mains wiring has a filtering effect and distorts the radiation pattern. You also run the risk of confusing one noise with another as they all tend to have the same buzzy sound. I don't know what others think, but I reckon you'll get a very confused picture if you work on anything but the fundamental and maybe the low harmonics. __________________ Andy G1HBE.