Looking to see if this rings a bell with anyone. I get a background hum in all AM radios in my house, including in a wired detached garage. Even in the car, but it goes away when I back out of the garage. I remember dealing with a stereo ground loop hum problem some time in the past, and “ground” sticks in my mind. Had a new service installed a few years ago, and i don’t recall the problem before that. Any ideas? Thanks in advance.
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Radio Hum
I got the same problem, but I know what is causing it, It's a leaking electrical tranformer about 150 feet from my house which I confirmed by driving toward it, the closer I get the louder is gets on my radio; gas + electric wont do anything about It, inside I just spin my radios around until it stops.
Well of course the stock explanation is that they don't know the words, but the other poster may have had it right -- situations like this seem to be due to a nearby pole transformer, though I've never quite figured out the mechanism involved.
Of course, another explanation could simply be metal siding or foil-lined drywall or insulation attenuating you signals.
In simple terms, anything 'electronic' or with a transformer in it can be causing the hum. It can be a flourescent light ballast, a streetlight, or even by having a loose wire nut..
You need to run down the source. You do this by first turning off ALL the power in your house. Does the car radio still have the hum? If so, the problem is not in your house.
If the noise has gone away, the source is in your house. Now, turn 'on' all the breakers on the left side of your panel. Has the hum returned? Continue this way, until you have identified the circuit that's causing the hum. Once you've found the breaker, find ALL the loads (appliances, lights, etc.) on the circuit. Check the loads one at a time to see just where it's coming from. If the problem is there with all loads disconnected, then the problem is in one of the wire connections.
A simple magnetic device such as a transformer won't cause hum (except the audible hum you hear when you're next to that device). To have hum that can get into radio reception (especially when the radio isn't plugged in) you need some nonlinearity to produce RFI, and a simple transformer doesn't contain any nonlinear components. However, a bad connection can have nonlinear characteristics, and arcing inside/around a HV transformer will most definitely be nonlinear, and I suspect that many of the transformer-related interference scenarios are due to either/both of these two causes. (Plus it's not clear what other components may be in modern pole transformers that could cause problems.)
Other nonlinear elements are things like dimmers, speed controls, electronic switches, fluorescent lights, etc.
Turning off house power and seeing if battery radios still pick up hum is a good test, but not a slam-dunk on separating inside vs outside causes. If you turn off power at the breaker panel you also turn off the "antenna" that the power lines in your house are providing for any potential external sources, so external-sourced hum is apt to be reduced (though not completely eliminated).
Here's a simple test that proves...............?
AM radio plugged into detached garage. LV lights on in house. Hum
unplug and run on battery power in garage. No hum or negligible noise.
Radio plugged in, turn off LV lights in house, no hum
Same goes with 4 two bulb electronic ballast fl. lights when on-hum, off-no hum.
Odds are the LV lights have an electronic "transformer".
And the fact that unplugging can eliminate the hum shows how the house wiring can serve as an "antenna" (or in this case an RF cable).
And the fact that unplugging can eliminate the hum
shows the wiring can act as an antenna?
Really, I thought it might show that the transformer hum somehow made it's way back to the garage via the connection to the house service panel.
"(or in this case an RF
"(or in this case an RF cable)"
The RFI is traveling over the regular electrical wiring. Likely if one listened closely one could detect the RFI even with the radio unplugged, but having the radio plugged in carries it directly into the radio chassis.
Low voltage lights.
These do it in our house and also carry over to the detached garage that runs off a sub panel pulled off the house service. No electrician but I guess this adds to the transformer issue mentioned by others.