My bedroom:
A TV hung on a wall. A ceiling fan on a wall switch. Both in the same breaker circuit.
Often, TV reception over the air gets pixelation or no reception at all with fan on low speed. Gets fine at high speed.

 

My bedroom:
A TV hung on a wall. A ceiling fan on a wall switch. Both in the same breaker circuit.
Often, TV reception over the air gets pixelation or no reception at all with fan on low speed. Gets fine at high speed.

Very rough guess, the noise produced by the fan on low speed is at a frequency that isn't getting filtered well while the high speed noise is.

 

I'd put a filter on the TV cord... Reminds me of the old days of TVs and kitchen mixers or vacuum cleaners.

 

Put a filter at the fan housing wiring connection if possible too. If it's generating EMI, reduce it at the source.

 

Is it on a triac phase-fired dimmer at low speed, and connected directly to the supply at high speed?

 

No triacs, no dimmers. Just a plain wall switch. Stock everything, nothing modified.

 

No triacs, no dimmers. Just a plain wall switch. Stock everything, nothing modified.

But, inside that thing, there is some means of changing the speed and if it uses triacs, those will generate quite a bit of noise to produce the low speed whereas if it is effectively connected directly to the mains at high speed, that noise will be absent. I suspect that Ian0 has hit on the core source of the behavior.

 

Have not opened it; Another fan like that has 3 capacitors in one package to select the speed. I think they go in series with a winding for the 3 speed selection.

 

Exactly, it goes in series with the motor’s winding. The switch mechanically steps thru 3 states plus the fully disconnected