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What causes this
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Gyro:
I suspect that a lot of the interference from these lamps comes from the cheap un-snubbed mains bridge rectifiers.
NiHaoMike:

--- Quote from: james_s on September 29, 2020, 05:51:15 pm ---Is there a power factor requirement? Either way the LED bulbs that lack switchmode drivers are crap, they flicker at 120Hz which I can't stand. It's not that hard to make a clean switchmode driver, you just have to buy decent quality bulbs.

--- End quote ---
There is a requirement although I'm not sure exactly when it applies. Making them flicker free is just a matter of using large enough capacitors.
richard.cs:

--- Quote from: NiHaoMike on September 29, 2020, 10:15:31 pm ---
--- Quote from: james_s on September 29, 2020, 05:51:15 pm ---Is there a power factor requirement? Either way the LED bulbs that lack switchmode drivers are crap, they flicker at 120Hz which I can't stand. It's not that hard to make a clean switchmode driver, you just have to buy decent quality bulbs.

--- End quote ---
There is a requirement although I'm not sure exactly when it applies. Making them flicker free is just a matter of using large enough capacitors.

--- End quote ---
In the EU there is not a power factor requirement for LED lamps as switch mode supplies under 75 W (apparently it's in EN61000-3-2) are exempted from it.

Of course we have established that the RF noise source the OP asked about is not a SMPS at all but something rather more weird.  :)
richnormand:

--- Quote from: richard.cs on September 29, 2020, 03:38:52 pm ---Certainly at least some of that style use switching regulators.

Wait, no that is very clearly a filament lamp with real, tungsten, filament. No LEDs there at all. I know what's happening.  :)

I have heard about it before with this type: http://www.lamptech.co.uk/Spec%20Sheets/IN%20WC%20D%20Ediswan%20Beautalite.htm but the long wire filaments of the type in the article are probably vulnerable to it as well. Essentially they are often vacuum filled (particularly as the uncoiled filament would have too much convective loss if they were gas filled) and at certain points in the mains cycle is is energetically favourable for the electrons to jump off the tungsten part-way along and fly through the vacuum down to the other end and hop back on. In doing so various RF oscillations can occur as they get pulled into spiral paths by the local magnetic fields and the radiate RF energy in a magnetron-like way.

Read a little about it here, but it seems like a known problem. https://www.emcrules.com/2017/04/can-incandescent-light-bulbs-cause.html That article talks about interference in the FM broadcast band which is immediately adjacent to the air band.

--- End quote ---

Sounds like Barkhausen oscillation sometime seen in old tvs? The oscillations could be very high frequencies and leave noise on the image. Since they were generated often by the horizontal drive tube (valve) it would be synchronized with the deflection and thus leave a thick stable vertical line on the screen. They could also be picked up on AM and shortwave radio. You could buy a small magnet clamp to affix to the glass tube and position it to eliminate the effect.

james_s:

--- Quote from: NiHaoMike on September 29, 2020, 10:15:31 pm ---There is a requirement although I'm not sure exactly when it applies. Making them flicker free is just a matter of using large enough capacitors.

--- End quote ---

Large enough capacitors are expensive and bulky, using a switchmode driver allows them to be much smaller. I've never seen a linear LED lamp driver that didn't flicker.
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