I have a noise in my HF radio besides the bad power line noise the power company is working on. I tracked it down the the light/ceiling fan in the room my radio is in. The fan switch is broke so when the light switch is turned on the fan and light turn on and both go off when the switch is turned off. The noise is just in 20m and 17m. When you turn the fan/light on I get about 2 S units of noise in 17m which is not surprising since the light has a CFL bulb in it..

Where we get into the twilight zone is on 20m. The fan/light is turned on and off with a regular light switch on the wall, no dimmer or anything just a plain light switch. When the fan/light is turned ON the noise goes DOWN about 5 S units and when I turn the fan/light OFF the noise goes UP about 5 S units. When the fan/light  is turned on, less noise, turned off more noise.

Any thoughts?????????

My guess is that the switch has a problem. Trip the breaker and see if the noise goes away. I bet it does. Somehow in the off position it is generating rf

bad connections can do that

just a guess


is there a GFCI on the circuit?

No gfci.

This would be my guess as well. Or a bad connection/splice somewhere else in a daisy-chained circuit which is generating noise, and when switching off you're changing the resonant length of the wire.

Easy and cheap enough to change the switch.

Bad switch, or a loose connection somewhere in the power system that gets better under load.

At a minimum I think I'd be tightening the connections at the breaker, switch, and fan.

Based on your description, I doubt it's the switch but you never know.. When the switch is on, it may have a poor connection and generate lots of interference, kind of like a miniature spark-gap transmitter. The fluorescent bulbs are known to ruin cheap light switches. It makes the switch arc a lot when the bulb is switched on and off. Also, any inductive loads, like motors, can cause spikes in voltage due to self-induction when the load is turned off. Usually a bad switch will generate RFI when the circuit is on. It also has RFi spikes when the load is turned on and off. I doubt the switch is the problem if the noise is lower when the switch is off.
You problem may also be caused by another device in the same circuit, like a dimming light switch or a pulse type (switch mode) power supplies. Turning the light switch on, creates a different path for common mode currents thus reducing the noise. Try to find out what else is on the same breaker and try to isolate the problem. The RFI noise may get to the radio through grounding (if any ) or the power circuit, as well as the coax shield.

Step #1 would be to ditch the CFL for an incandescent bulb. If that clears it up, try an LED bulb.

I haven't done anything to anything but I thought I would try it today, a short while ago  The switch for the fan/light now does nothing to either freq. The S meter doesn't move now when I flip the switch on and off.