OT - radio interference
Archiver
Posts: 46,084
hi -In the space that I work on electronics in I get a strong audio
signal over the powerline from a radio station. The station is in
Spanish and the frequency is around 1600 khz. If something is plugged
into the wall outlet with a speaker on it, you can pretty much bet
that the radio station is going to be heard quite loudly. I've asked
other people in the building and they have the same problem. I'm
located near downtown Los Angeles (Echo Park).
I can get the same problem even with battery powered circuits, but
it's much worse when connected to the mains
Is there anything that can be done about this? Who's problem is this
- mine, the power company, the building owner, the radio station,
god, fcc?
signal over the powerline from a radio station. The station is in
Spanish and the frequency is around 1600 khz. If something is plugged
into the wall outlet with a speaker on it, you can pretty much bet
that the radio station is going to be heard quite loudly. I've asked
other people in the building and they have the same problem. I'm
located near downtown Los Angeles (Echo Park).
I can get the same problem even with battery powered circuits, but
it's much worse when connected to the mains
Is there anything that can be done about this? Who's problem is this
- mine, the power company, the building owner, the radio station,
god, fcc?
Comments
We have the same situation here at work. The station is about a mile down
the road. In general, stuff sold to the public is not shielded very good.
The person (speaking of an individual, not a company here) causing the
interferance (though he/she may be operating totally within the law, and can
prove it) generally gets the blame for causing the problem, and many times
must make changes on his/her end<G>.
However, in reality with a commercial station, a strong station
nearby, not much you can do about it. There are ways to locally limit the
interferance (again at arrl), but it's sort of like living next to a large
airport<G>. It gets into the power lines, and being a relatively low
frequency, the power lines re-radiate it for miles. We recently had an
engineer who was offended and did spectrum analysis, pictures, the whole
tomalie. Found that the offending signal was on the ground wires and even
the metal in the building. He would up building copper circuit board condos
over his sensitive circuits<G>.
Do you have a specific problem that could be addressed?
Original Message
From: markallen [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=GfoAechUvb9hPCkuNWkNIzI4rurZu0jz-tc3mBPNQPaISqMKFkHpZ61EzNBmK05EfVzV2NjEGJM3wp_lI4hIU5AY]markallen@m...[/url
Sent: Wednesday, December 10, 2003 3:38 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] OT - radio interference
hi -In the space that I work on electronics in I get a strong audio
signal over the powerline from a radio station. The station is in
Spanish and the frequency is around 1600 khz. If something is plugged
into the wall outlet with a speaker on it, you can pretty much bet
that the radio station is going to be heard quite loudly. I've asked
other people in the building and they have the same problem. I'm
located near downtown Los Angeles (Echo Park).
I can get the same problem even with battery powered circuits, but
it's much worse when connected to the mains
Is there anything that can be done about this? Who's problem is this
- mine, the power company, the building owner, the radio station,
god, fcc?
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
A few years ago - I had to design and install some audio
equipment near a " main frame " computer .
So I think you can guess actually it was quite a few years ago : )
And to make a long story short .
I was able to get it to work . The circuit was centered around a
variable audio attenuater .
At the input I installed a very small capacitor , to signal ground .
I started with the smallest " cap " that I had in my
" Low value , hi volume , temporary storage area " - [noparse][[/noparse] Junk - Box ]
. And kept increasing the caps value
until I started to " lose " the top end of the audio signal .
Then backed off a little .
Good Luck
>
>
>
>
>
>
use of ceramic caps (in the pf range) to shunt a variety of "antennas". One
thing to note that most of the time the RF signal isn't being imposed on the
powerline, but other support wires. For instance, while there's not
sufficient power coupling directly into a speaker lead to get into the
speaker directly, the wire lead acts like an antenna which routes the RF
into the power amplifier itself. Many power amps use a large amount of
negative feedback to keep the distortion low, and if that feedback loop
doesn't have enough slew-rate, the stray RF can modulate the feedback loop.
Shazzam, a CB radio comes blasting through your really big PA system in a
bar gig. (been there done that). After that I started putting tiny caps on
the inputs of all my speakers.
One time I actually heard a radio station that was getting into the phone
lines that had a dial-up modem. While trouble shooting the problem I heard
the DJ dial a phone number on-air, and it was loud enough to caused that
line to dial the same phone number. Turned out that problem was a ungrounded
conduit the phone lines were run through. A ground strap corrected that
problem.
This might also be an issue with any sort of computer/clocked devices (yes,
the Basic Stamp, etc) which can cause radios, TVs, and home theaters to
whine, chirp, and generally misbehave. That's what ferrite beads are all
about.
Mike Sokol
" One should not increase, beyond what is necessary,
the number of entities required to explain anything"...
-William of Occam-
Original Message
From: "markallen" <markallen@m...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, December 10, 2003 3:38 AM
Subject: [noparse][[/noparse]basicstamps] OT - radio interference
> hi -In the space that I work on electronics in I get a strong audio
> signal over the powerline from a radio station. The station is in
> Spanish and the frequency is around 1600 khz. If something is plugged
> into the wall outlet with a speaker on it, you can pretty much bet
> that the radio station is going to be heard quite loudly. I've asked
> other people in the building and they have the same problem. I'm
> located near downtown Los Angeles (Echo Park).
>
> I can get the same problem even with battery powered circuits, but
> it's much worse when connected to the mains
>
> Is there anything that can be done about this? Who's problem is this
> - mine, the power company, the building owner, the radio station,
> god, fcc?
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>