Radio interference with PC speakers


E

Ed Coolidge

I was just wondering if anyone has ever experienced radio interference with PC
speakers. At first I thought that it was just static, but if I listen carefully
I can actually hear a local station through speaker, and only the left one at
that! I suspect that the problem is that the speaker is poorly shielded, but
it's just weird that it's one particular station instead of pure static.
 
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D

David Maynard

Ed said:
I was just wondering if anyone has ever experienced radio interference
with PC speakers.
Not my PC speaker but my component stereo system used to pick up (probably
through the turntable cartridge) a paging system from the hospital that was
around the corner where I used to live.
At first I thought that it was just static, but if I
listen carefully I can actually hear a local station through speaker,
and only the left one at that! I suspect that the problem is that the
speaker is poorly shielded,
PC speakers, especially low cost ones, aren't usually shielded at all,
being low frequency (audio) devices that don't generate any interfering EMI.

Magnetically 'shielded', yes, to prevent distorting the CRT, but not EMI.
but it's just weird that it's one particular
station instead of pure static.
Not as weird, or unusual, as you may think. Just guessing but it's probably
a strong local AM station as AM is super easy to demodulate. All it takes
is a rectifier, low pass filter, and some amplification: all rather
'natural' aspects of a typical transistor audio amp.

That won't 'tune' a station, though, which is why it'll only 'work' for
something local with sufficient power in the area to surpass background
noise; plus enough signal so that the amp can make it audible.

That's why it's more common on amps with a phono input: a lot more gain.
 
I

I of the Storm

Ed Coolidge said:
I was just wondering if anyone has ever experienced radio interference with
PC speakers. At first I thought that it was just static, but if I listen
carefully I can actually hear a local station through speaker, and only the
left one at that! I suspect that the problem is that the speaker is poorly
shielded, but it's just weird that it's one particular station instead of
pure static.
My bass amp used to pick up Spanish radio in my dorm room. (Too bad I don't
speak spanish, I guess.)
 
E

Ed Coolidge

David said:
Ed Coolidge wrote:
Not as weird, or unusual, as you may think. Just guessing but it's
probably a strong local AM station as AM is super easy to demodulate.
All it takes is a rectifier, low pass filter, and some amplification:
all rather 'natural' aspects of a typical transistor audio amp.

That won't 'tune' a station, though, which is why it'll only 'work' for
something local with sufficient power in the area to surpass background
noise; plus enough signal so that the amp can make it audible.

That's why it's more common on amps with a phono input: a lot more gain.
Actually it's FM. There are several stations in the area and I'm not sure which
is closest. Usually when you say that you're hearing voices people tell ya to
see a shrink! It's good to know that I'm not going crazy. ;)
 
S

Spajky

I was just wondering if anyone has ever experienced radio interference with PC
speakers. At first I thought that it was just static, but if I listen carefully
I can actually hear a local station through speaker, and only the left one at
that! I suspect that the problem is that the speaker is poorly shielded, but
it's just weird that it's one particular station instead of pure static.
maybe soldering a small bypass capacitor (few nF) to PC speakers vol.
pot could cure that symptom...
 
D

David Maynard

Ed said:
Actually it's FM.
So much for my guessing ;)
There are several stations in the area and I'm not
sure which is closest.
Well, it depends on the power output too. The strongest should be the one,
unless there's something in the amp acting as a semi 'tuner'.
Usually when you say that you're hearing voices
people tell ya to see a shrink! It's good to know that I'm not going
crazy. ;)
Man, you should have heard the voices in the hospital pager. Louder than
the music, it was. And preceded by an ear splitting beep-bleep-blurp.

Dern near had a heart attack the first time that kicked on.
 
A

Al Dykes

I was just wondering if anyone has ever experienced radio interference with PC
speakers. At first I thought that it was just static, but if I listen carefully
I can actually hear a local station through speaker, and only the left one at
that! I suspect that the problem is that the speaker is poorly shielded, but
it's just weird that it's one particular station instead of pure static.

yup.

It was an office that was about half a mile from the Empire Satate
building, which has a bunch of FM and TV antennas oon the top, and
probably some other signals. The computers on the side of the office
that faced the ESB had almost-listenable radio sound comming out of
the speakers, whihc were the cheapest possible external crap. We
tried a few cheapo models and found one that didn't pick up
interference and bought a bunch of them at $15/pair.
 
T

T Shadow

Not the computer speakers. My home stereo speakers pickup police car
broadcasts as they drive by. Even when the receiver is turned off!
 
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C

Conor

Ed said:
I was just wondering if anyone has ever experienced radio interference with PC
speakers. At first I thought that it was just static, but if I listen carefully
I can actually hear a local station through speaker, and only the left one at
that! I suspect that the problem is that the speaker is poorly shielded, but
it's just weird that it's one particular station instead of pure static.
Actually it is more to do with the length of the speaker cable. It acts
as an antenna and the frequency it'll pick up depends on the length of
the cable.

Try getting a ferrite rod and wrapping the speaker cable round it a few
times.
 

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