The electrical noise environment in a radio station can be as contaminated as the Gulf.
I tried tracing one noise and found a whole string of other noises. Let's take them one at a time.
Every night, just after sundown, a static buzz pops on the entire upper end of the AM band, gets louder over two minutes, and when it's super loud, it shuts off for a minute before repeating the cycle.
The other night I tuned a portable to a blank AM frequency and walked all over the building, wondering if the buzz would be louder in certain areas, but it was the same strength everywhere, suggesting it's coming in over the power wiring from an outside source.
During the course of moving the radio around, I was surprised to hear a blast of fizzing noise within several feet of the cable telephone modem, which is not a Wi-Fi device, and I had it on a shelf right where I sit. I didn't like the idea of sitting in a stew of digital noise, so I moved the modem over to a distant shelf where the microphone control box was, and put the mic-box where the modem had been.
A new trouble arose, as the matching transformer in the mic-box picked up a loud and constant hum. I re-tested the shelf area using the AM radio, and heard very loud switching power supply noise that sounded like a military bull-dozer, coming from the bottom shelf power supplies.
To make the microphone hum vanish, it was necessary to move the mic-control box five feet to a newly installed shelf.
The best way to solve studio noise problems is to take dancing lessons.
is not fun, especially if there is more than one source of noise. One suggestion for determining if the noise is from the power lines and/or devices inside the building is to turn off the main breaker and check if the noise changes or goes away.
Neil
I had to resort to turning off the Main breaker at one of our Fire Stations complaining of noise getting into their PA system and radios.
This was a crakley buzz, constant. Once we determined it came from within by shutting off the Main, we flipped breakers one at a time to narrow it down.
The problem was found to be caused by a leak in the roof directly over a junction box in the attic. I advised them to leave the circuit off until they got the problem cleared up. That was over a year ago. The breaker is still off...
FIRE!
IN THE FIRE STATION!
Carl, your first noise sounds like
a street light coming on at sunset.
But - something is wrong with it.
When the light gets up to full brilliance,
somethng goes wrong and it shuts off
again. This repeats.
I had this exact thing happen.
Does that sound like it makes
any sense?
Bruce, DOGRADIO
Those stupid power cubes
and switching supplies can
drive you crazy.
My cell phone charger is a tremendous
noise blaster.
Sometimes you can relocate noise sources
or even move/rotate equipment if possible.
In my case, with mostly everthing disassembled
(until we know about our living situation) I have
the luxury of unplugging things I don't need right
then. Unfortunately, Carl, at KDX you probably
can't do that, because you have so many things
running at once.
Bruce, DOGRADIO
Bruce,
That was exactly my thought. I once stood in fascination near a big mercury vapor street light watching it cycle. It started dim, slowly brightened and then shut off. Then it cycled over and over all the while putting out a fairly loud humming sound. I thought it was going to blow up.
In home sources of noise are numerous. Fortunately most are short range. Hold a portable radio within a few inches of anything with LED, LCD or gas discharge displays. Even a remote control emits strange noises nearby. Switching power adapters always put out noise within a few inches, some much farther.
Old CRT TVs were always major noise offenders. Modern TVs, not so much with one big exception: PLASMA TVs. They're worse than the old CRT TVs.
Surprisingly, I've never found fluorescent and CFL lights to be major offenders. Sure they put out noise, but not as bad as some other in home sources.
Likewise, I've never found my computers to be big offenders. Not so for the monitors. I think computer monitors of any type are the major noise sources related to computers.
Lamp dimmers for both incandescent and fluorescent are guaranteed to put out noise, particularly at settings toward the dimmer side.
The one breaker at a time technique for isolating an in home noise source is the absolute best method for finding a culprit. Trouble is, it seems like nobody wants to go to "all that trouble".
Brucedog, PhilB, the streetlight theory seems right because the noise distinctly begins right after dark.
I have thought to visually watch the three streetlights viewable from the porch and they appear normal, but many more streetlights stand behind trees and buildings, so we need to go on a spotting mission some night with a portable radio in hand.
To ward off suspicion I'll rent a dog and leash so I look like a regular guy. I could even buckle the radio onto the dog so that it would sound like an electric pet. I'll tell people the dog has gas.
Yes, Part 15 is the lifestyle for me.
I found the street light RFI situation
to be very interesting. The light was
right across the street from my house,
so it was obvious what was going on.
(To me, anyway.) I am on a very busy
street, traffic wise. And, thankfully, sure enough,
somebody called the problem in to the
power company. It was a good thing,
because in that area, it was pretty dark -
in other words - the other street lights
were pretty far away - there just wasn't
enough ambient light for pedestrians there.
Then I came home one
night and the light was on all the time.
The RFI had disappeared.
So yup, I go with the street light theory.
If that is true, then I wonder how far away
it is from you, Carl? I also wonder how far
that RFI can travel?
Some people looking for RFI take 2 radios.
One is on the AM BCB. The second one is
in the aviation band (good old amplitude modulation)
that runs from 108 to 136 MHz. Experienced RFI chasers
say that the aircraft radio will tell you when you are really
close to the source. (????)
Bruce, DOGRADIO
At 6 AM this morning it was still dark out, I tuned to 1680 AM where no local stations are on at this hour, and morning skip was stirring with voices from far away.
The offending 2-minute off and on buzz was there, but sounds far away like it isn't in the immediate vicinity.
Can a goofy street light be heard a mile or more away?
Maybe it's in Chicago or Kansas City.
I'd planned to record it so I could go on about it for awhile longer, but its moving out of area.
Maybe tonight after dark it will come in well enough for a good capture.
<cite>Can a goofy street light be heard a mile or more away?<cite>
Yes, especially if arcing is happening. Remember back in the day we used sparks for transmitters.
Tonight just after dark I was returning to the station when I passed a real buzz-causer which caused me to look up, and THERE IT WAS!
A street light flickering in it's failing attempt to turn on, and failing, over and over again, all night, and week after week.
THERE IT WAS, the noise that has been exterminating my AM signals every night for a very long time.
Let's analyze the situation.
The people living near that lamp A.) Don't care and haven't reported it; B.) Have reported it but the electric company doesn't care and never bothers to fix it; or, C.) Something I haven't thought of which would explain everything in some other way.
In any case I will go down there in the daytime, get the lamp-pole number, phone the electric company, and report the situation by mentioning the RF disturbance to the rado bands, something an average person wouldn't realize.
If it isn't fixed in five years I will step up my effort.
It's pretty cool when you find it, huh?
Great job!
Bruce, DOGRADIO
Carl said: "If it isn't fixed in five years I will step up my effort".
They should be surprisingly respnsive from what I have seen on the web. Street lights are there for safety reasons, similar to traffic lights. Each municipality has its own rules, but in general, they all seem to give them high importance (law suit probability?). Let us know the outcome.
Yup, Phil, I think you are right because - -
the street light that caused the problem
here was fixed pretty fast. It took me
about a week of listening to the interference
to figure out what it was. It would have
taken less time if I had less to do at that
point. When I figured it out - about 3 days
later it was fixed.
I was going to call the utility - but I didn't
have to. By the time I got around to
thinking about that the interference was
gone and I got the AM BCB (and most of the
HF spectrum back.
Bruce, DOGRADIO