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Author Topic: Buzzing noise on receiver when I leave light switch turned off  (Read 835 times)
KU4UV
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Posts: 407




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« on: May 20, 2016, 08:33:35 PM »

 Huh   This is puzzling me.  I just completed construction on a Sawdust Regenerative receiver kit today.  I am using it in my apartment, which is at ground level, with a random wire about 40 feet long outside the window.  I have a laundry room next to my ham bench that has a single light fixture in it.  I have noticed that when I flip the switch to turn the light off, I actually get a buzzing noise in the receiver.  When I turn the light switch "on"  the buzzing stops.  This is odd, as you would think it would be the opposite.  I pulled the light bulb out of the socket, and even with nothing in the socket, the buzzing noise is there when I flip the switch off, but it disappears when I flip the switch "on."  I'm not sure what might be going on here, unless maybe there is some sort of arching going on in the switch itself, or the switch was wired incorrectly?  If it were wired incorrectly though, it looks like the light would be going on when the switch is in the down position, and off when it is in the up position.  The apartment was built back in the early 80's, so the switch may be going bad.  I might try replacing the light switch tomorrow and see if that does anything.  Any ideas on this one?  Thanks gang!

73,
KU4UV Mike
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K5LXP
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« Reply #1 on: May 21, 2016, 06:15:17 AM »


One thing that comes to mind is that the interference on the AC line gets attenuated through the light when you turn it on.  Maybe try turning on different devices on this circuit and other circuits to see if you can narrow it down.

Mark K5LXP
Albuquerque, NM
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KU4UV
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« Reply #2 on: May 22, 2016, 11:59:16 AM »


One thing that comes to mind is that the interference on the AC line gets attenuated through the light when you turn it on.  Maybe try turning on different devices on this circuit and other circuits to see if you can narrow it down.

Mark K5LXP
Albuquerque, NM

Thanks, I tried replacing the light switch last night, but that didn't help.  It's kind of strange the way they have the circuit wired, as all of the electrical circuits in the bathroom are all going through that one light switch as well.  I noticed that last night when disconnected power to the light switch and then applied power without the switch, the lights and fan in the bathroom went out. 

73,
Mike KU4UV
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K5LXP
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« Reply #3 on: May 22, 2016, 07:56:26 PM »


Pretty common to wire lights and fans from the same wall switch.  Did the noise go away when you had the breaker off?  Not sure of your vintage of house but anymore bathrooms and kitchens need to be fed via GFI, so if you had one of those outlets in the bathroom you could see if that's where the noise is coming from.


Mark K5LXP
Albuquerque, NM
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KU4UV
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« Reply #4 on: May 23, 2016, 12:00:23 PM »

I believe it does when I flip the breaker that particular circuit is on.  There is a GFI in the bathroom, so not sure if that is casing some buzzing or not.  The house is about 35 years old, so it may be time to start thinking about replacing some of these old switches, outlets, and the GFI.
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AA4PB
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« Reply #5 on: May 23, 2016, 12:41:00 PM »

The lights and fan are not required to be on a GFI. Only outlets where you can connect a plug and cord are required to have GFI in the bathroom. It is common to have the lights and fan controlled by the same switch. It is common to have the lights/fan powered by the same breaker as the GFI outlet.

Have you tried pressing the test button on the GFI outlet to see if the RFI goes away? If it goes away that could be an indication that the GFI outlet is bad. They also may have fed power from the breaker to the box containing the GFI outlet and from that to the light/fan switch. Turn off the breaker and check all the connections (wire nuts and screws) in the GFI outlet box to see that everything is tight and no sign of overheating. I'm thinking that some connection could be arcing with little load but quiet down when you place the load of the light and fan on the circuit.

Do the lights and fan go out when you press the test button on the GFI outlet? If so, that indicates that the lights and fan are (unnecessarily) fed from the output of the GFI breaker and it's a pretty good indication that the GFI is causing the RFI.

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WX7G
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« Reply #6 on: Yesterday at 05:40:52 AM »

The "fix" is to leave the light switch ON.
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KU4UV
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« Reply #7 on: Yesterday at 06:31:01 AM »

The "fix" is to leave the light switch ON.

Yeah, that's one way to fix it, but that gets expensive after a while.
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KD0REQ
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« Reply #8 on: Yesterday at 09:44:55 AM »

any place where you could stretch out as far as you can (believe exact distance in code is 6 feet) from water or moisture needs a GFI.  including things like whirlpool tubs and wetproof lights over a shower.

every outlet in my Ham Cave shed outside is individually GFId.  nice and quiet.

bathroom fans are almost always shaded-pole motors, electrically quiet.

either the GFI is nuts, there is an arc at a bad connection, or you have one of those fancy-Dan CFI or LED lights in the bathroom (or an old fluorescent with a starter can) that is acting up.  time to troubleshoot individual items here.  replace whatever is radiating.
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KU4UV
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Posts: 407




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« Reply #9 on: Yesterday at 02:02:37 PM »

any place where you could stretch out as far as you can (believe exact distance in code is 6 feet) from water or moisture needs a GFI.  including things like whirlpool tubs and wetproof lights over a shower.

every outlet in my Ham Cave shed outside is individually GFId.  nice and quiet.

bathroom fans are almost always shaded-pole motors, electrically quiet.

either the GFI is nuts, there is an arc at a bad connection, or you have one of those fancy-Dan CFI or LED lights in the bathroom (or an old fluorescent with a starter can) that is acting up.  time to troubleshoot individual items here.  replace whatever is radiating.

The only other electrical items in the bathroom are the overhead fan, overhead heater unit which is on a rotary switch, and a light fixture vanity over the bathroom mirror which has four bulb sockets.  There aren't any fluorescent balasts that would be acting up.  I am most likely going to replace the GFI and the two switches controlling the light fixture and fan and see if this fixes the problem.  Thanks to everyone for your responses and suggestions.

73,
Michael KU4UV
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