[Spirit]

Here's the deal:
Last year we did some renovations in our home and we installed new potlights in our kitchen and family room.  Unfortunately, when I listen to my little bedside clock radio before bed, I get an awful electrical noise coming through the radio speaker when the potlights downstaris are turned on.  The noise goes away instantly when the lights are turned off.
The electircal noise is worse when I am tuned a little off the station and seems to dissipate when I am tuned properly on the local station.  This is happening only on AM band. I believe that this noise stems from the potlight transformers.
So, I did a little experiement.  I unplugged the radio and took it down to the basement and plugged the radio into my deidcated AC line that I use for my audio system and the noise was the same. I plugged into my power conditioner - same thing.  Putting my ear directly on the tweeter of my speakers didn't result in much noise at all, but it leads me to think
that even though I don't hear the noise listening to my system - the grunge must be coming through somehow.  Any explanations, suggestions or comments would be appreciated.

[Bob Reynolds]

I'd guess RFI based on your description.

[BradJudy]

It could just be that you're picking up the noise through the clock radio antenna, not the power lines.  Particularly since you said it only happens on AM, not FM.

[Russell Dawkins]

do you have a dimmer on your pot lights?

[Spirit]

do you have a dimmer on your pot lights?

Yes I do have adimmer, but the noise seems to be constant whether the dimmer is high or low.
BTW - the same noise comes through my transistor radio that is NOT plugged in! Operates on batteries and the same darn noise.
Any electrical engineers out there that can help?

[Russell Dawkins]

Yes I do have adimmer, but the noise seems to be constant whether the dimmer is high or low.
BTW - the same noise comes through my transistor radio that is NOT plugged in! Operates on batteries and the same darn noise.
Any electrical engineers out there that can help?

I am not an engineer, but the fact that the noise is independent of the radio being plugged in tells you the noise is not coming down the powerline, but RF noise. Dimmer systems make the most noise when between extremes of high and low. Often they are silent when the light are full on, but only then. The transmitting "antenna" for the RF noise is the wiring between the dimmer unit and the lights and the noise itself is an artifact of the switching off and on by the dimmer of the power to the light to achieve the dimming effect. Brighter has a longer on cycle than off and dimmer has longer off than on.

Perhaps a real engineer can chime in with a possible fix. 1:1 coupling transformer? Would a ferrite collar around the output to the lights work? A cap across the output?

[Dan Banquer]

Try an AC line Filter, such as a Tripplite Isobar, or if your into DIY try the Felicia project listed in the lab forum of Audiocircle.
                 d.b.

[JLM]

d.b.,

Can't be A/C power issue as he gets the same with a battery powered radio.

It's probably the dimmer (surely some are better than others).  I'd change out the dimmer for a simple on/off switch and see if that helps.  Keeping dimmers away from audio equipment is pretty standard advice.

[Spirit]

d.b.,

Can't be A/C power issue as he gets the same with a battery powered radio.

It's probably the dimmer (surely some are better than others).  I'd change out the dimmer for a simple on/off switch and see if that helps.  Keeping dimmers away from audio equipment is pretty standard advice.

Thanks for all the comments so far.
I am not sure how much logicical thinking goes into this kind of thing but here goes any ways:
I have other dimmers in the house (bathrooms, basement, dining room - we are a very dim family!)
but the problem only happens with the 2 rooms mentioned in my opening comments.
Logic dictates that it must be the pot light transformers.  Any comments and suggestions.
Thanks

[PhilNYC]

This seems like a perfect situation to see whether Shakti stones or ERS clothe really makes a difference...

[Dan Banquer]

Here's more info:
http://www.audioholics.com/techtips/audioprinciples/interconnects/bulletproofingsysteminterf.php

d.b.

[Wayner]

Transformers are an electro-magnetic device. They change voltage from one value to another through induction (120v to 12v) which is a 10 to one winding ratio. Many transformers are iron core and are built with sheets of steel stacked together and the bobbin coils are mounted in cavities within these laminates. Often times, the laminates are loose and you will hear a "buzz" from fluorescent or HID ballasts. This audible noise is from the laminates vibrating against each other (at 60 times a second). The other inherent problem with these transformers is they like to "broadcast". Unfortunately, the AM band is extremely susceptible to these types of noises. You here static during lightning storms or you may hear static when older cars or motorcycles drive by through most of the AM band. If you want to eliminate the noise, you will have to go to the source and that source is the transformers. Treating the A.C. lines will not help as you have proven that is not the source. Are the transformers mounted in a metal can? If so, is the can grounded. If the transformers are out in the open, can they be mounted into a metal box that then can be grounded?

W

[Dan Banquer]

"Treating the A.C. lines will not help as you have proven that is not the source. Are the transformers mounted in a metal can? If so, is the can grounded. If the transformers are out in the open, can they be mounted into a metal box that then can be grounded?"

I'm not so sure that the AC lines are not out of the equation. The device in question may well be not only radiating but also conductiing the radiated noise onto the AC lines. I would hazard a guess that it may well be both, so some experimentation from the user appears to called for.
                 d.b.

[Wayner]

I agree with JLM. I think because the noise was picked up by a battery operated AM radio, that the A.C. lines are not the culprit. However, perhaps they may be contributing a little. Hard to prove. I would trace the power from the pot lights back to the breaker box and see if the dedicated line to the hifi is on the same side. maybe a switch is in order there if they are on the same side. He still has an issue with RF, though and I think it is the largest contributor to the noise factor. Just my hunch.

Turkey is almost done!

Everyone have a good one!

[Russell Dawkins]

We still haven't heard whether the problem goes away when the suspect dimmer is on full brightness.
Also it seems to me this could be narrowed down by setting the dimmer 1/2 way to create the buzz then walking around with the radio and holding it first near the wiring to the lights and then near any other house wiring, like a power outlet or even the main breaker panel and comparing the intensity of the buzz.

Also, most portable transistor radios have the ferrite loopstick antenna across the upper edge. They have a null of sorts in reception in line with the ends of the antenna, so you can aim the upper edge of the radio so that you get minimum buzz and the the antenna is then pointing at the source of the interference.

You can test this by choosing a distant AM station of a known direction from you and orient the radio for minimum signal strength. At that point the radio's loopstick is pointing at the transmitter. To reiterate, maximum signal strength is achieved when the loopstick antenna is sideways to the signal.

[Steve]

I agree with both DB and Wayner. I would shield the tranny and I would also treat the AC line as it may be acting like an antenna.