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[email protected] March 8th 07 06:52 AM

Question about radio noise
 
Hi. I know nothing about amateur radio nor electronics so I'm here looking for
an answer to a question which bothers me. There are a number of places near
where I live that, if you drive by them with the AM radio in the car on, there's
an extreme amount of noise. It usually last while driving parallel to overhead
wires (not high power lines, must the ones on poles), then goes away. It's
always the same places and doesn't come or go. I'm guessing bad shielding of the
wires. My concern is, if it does this to the radio, is it harmful to people who
are near it? Thanks.


Steve Bonine March 8th 07 02:07 PM

Question about radio noise
 
wrote:

My concern is, if it does this to the radio, is it harmful to people who
are near it? Thanks.


The short answer is, no.

What you're probably hearing on your AM radio is noise caused by arcing
on high voltage lines due to defective or dirty insulators. Your radio
receiver is sensitive to this RF because, well, that's what radio
receivers do.

But the fact that you can hear it on your receiver does not imply that
it is harmful, any more than the fact that you can hear the local AM
station means that it's harmful. If you were in close proximity to the
AM station's transmitting antenna, you would be receiving exposure to RF
[Radio Frequency emissions] in excess of regulated maximums. But I
can't imagine a leaky high-voltage line putting out enough RF to be
dangerous even in close proximity.

See
http://www.fcc.gov/oet/rfsafety/rf-faqs.html for full details.

73, Steve KB9X


Rod[_4_] March 8th 07 06:45 PM

Question about radio noise
 
On Mar 7, 10:52 pm, wrote:
Hi. I know nothing about amateur radio nor electronics so I'm here looking for
an answer to a question which bothers me. There are a number of places near
where I live that, if you drive by them with the AM radio in the car on, there's
an extreme amount of noise. It usually last while driving parallel to overhead
wires (not high power lines, must the ones on poles), then goes away. It's
always the same places and doesn't come or go. I'm guessing bad shielding of the
wires. My concern is, if it does this to the radio, is it harmful to people who
are near it? Thanks.


All about power line noise and possible harm to humans at URL:
http://tdworld.com/mag/power_smarter...d=most-popular


[email protected] March 8th 07 08:34 PM

Question about radio noise
 
On Mar 7, 10:52?pm, wrote:
Hi. I know nothing about amateur radio nor electronics so I'm here looking for
an answer to a question which bothers me. There are a number of places near
where I live that, if you drive by them with the AM radio in the car on, there's
an extreme amount of noise. It usually last while driving parallel to overhead
wires (not high power lines, must the ones on poles), then goes away. It's
always the same places and doesn't come or go. I'm guessing bad shielding of the
wires. My concern is, if it does this to the radio, is it harmful to people who
are near it? Thanks.


Like Steve remarked, the noise you hear isn't harmful.

Overhead electric power distribution lines aren't shielded.
With time and exposure their insulators, even the wire
(if covered with insulation) will accumulate semi-conducting
dirt and grime. That can cause minor to major arc-overs
which are short-impluse energy spikes. Since those are
of very short duration their bandwidth is wide and can
spread the impulse energy up into the VHF range of
FM broadcast band.

In newer construction the electric power distribution
lines are underground, generally through metal conduit,
and don't get a change to radiate wideband RF energy
nor are there as many arc-overs.

If the irritation from picked-up noise is a bother, it can
be reported to the local power utility. It's touch and go
whether or not they do anything about it, though. It is
only an irritant to radio listeners and not harmful to any
human...but it is covered by FCC regulations as
"incidental, unintentional RF radiation" and has limits.

73, AF6AY



[email protected] March 9th 07 04:18 AM

Question about radio noise
 
Thanks much for the replies.


Ed Hare, W1RFI March 9th 07 05:26 PM

Question about radio noise
 
On Mar 8, 1:52 am, wrote:
Hi. I know nothing about amateur radio nor electronics so I'm here looking for
an answer to a question which bothers me. There are a number of places near
where I live that, if you drive by them with the AM radio in the car on, there's
an extreme amount of noise. It usually last while driving parallel to overhead
wires (not high power lines, must the ones on poles), then goes away. It's
always the same places and doesn't come or go. I'm guessing bad shielding of the
wires. My concern is, if it does this to the radio, is it harmful to people who
are near it? Thanks.


First, the levels of emissions are probably about a million times
lower than the standards for human exposure to electromagnetic fields,
so there are no safety concerns. See http://www.arrl.org/rfsafety for
more information on the subject in general.

The problem is generally caused by defective hardware on the poles,
from loose hardware to defective insulators (actually pretty rare.)

The subject is covered in detail at http://www.arrl.org/tis/info/rfi-elec.html,
especially relating to Amateur Radio.

73,
Ed Hare, W1RFI
ARRL Lab



Ed Hare, W1RFI March 9th 07 06:24 PM

Question about radio noise
 
On Mar 8, 3:34 pm, "
wrote:

but it is covered by FCC regulations as "incidental, unintentional
RF radiation" and has limits.


Congratulations on your license, Len.

It is probably best not to mx "unintentional" into that explanation
because under Part 15, "unintentional emitters" are treated
differently than "incidental emitters."

In the US, under Part 15 of the FCC's rules, power lines are
classified as "incidental emitters" -- devices that do not
intentionally generate RF signals inside of them, but that may do so
as an incidental part of their operation. Examples of incidental
emitters are electric motors or the power-line noise sources being
discussed.

Unintentional emitters are devices that do intentionally generate RF
signals internally, but that do not intend to radiate them. Examples
are computers, calculators and most digital devices.

Under the rules, indidental emitters do not have any specific radiated
or conducted emissions limits. The manufacturer of an incidental
emitter has a responsibility to use good engineering practice
(whatever that may be construed to mean) and the operator of the
device must do so in a way that does not cause harmful interference to
licensed radio users.

73,
Ed Hare, W1RFI
ARRL Lab



[email protected] March 10th 07 01:32 AM

Question about radio noise
 
On Mar 9, 12:26?pm, "Ed Hare, W1RFI" wrote:

The problem is generally caused by defective hardware on the poles,
from loose hardware to defective insulators (actually pretty rare.)


Hello Ed,

On my early-moring runs I've come across more than one pole that was
clearly a noise source. In the damp morning air just before dawn, you
can hear and sometimes see the arcing. PECO is pretty good about
fixing such things
because they often prevent a failure. But simple visual and
audible observations won't find all problems.

One caution: I have occasionally heard hams speak of
finding noise sources by climbing poles, or whacking them
with a sledgehammer to shake the loose hardware.

*DON'T DO IT!*

Besides being illegal, it's dangerous. And it won't
make utilities any more likely to fix RFI troubles.

---

Some may ask why the utilities don't just bury
all the wires. Four reasons:

1) The intitial construction cost is higher, as are any
changes in the future.

2) Finding and fixing problems can be a lot harder.

3) The utility has to deal with things like flooding of
underground facilities, people digging up high
voltage lines unintentionally, and rodents.

4) The transmission losses in buried power cables
are higher, meaning more energy is wasted.

73 de Jim, N2EY



Larry March 19th 07 02:38 AM

Question about radio noise
 
Steve Bonine wrote in
:

If you were in close proximity to the
AM station's transmitting antenna, you would be receiving exposure to RF
[Radio Frequency emissions] in excess of regulated maximums.


417 ft from the business end of WWKB's 50KW blowtorch in Hamburg, NY, the
former WKBW, a neighborhood popped up probably many years ago. Those
houses closest to the last tower in the chain, using the inverse square law
and the FCC database 4.2V/M at 1KM on two of the lobes, I figure there's
over 200 VOLTS/meter in their living rooms on Robin Lane.

I wonder how they get the flourescent lights in the kitchens to go out?
Can anyone have a stereo with external speaker wires feeding 200V/M back
into the feedback lines of the transistor amps without making it go nuts
like my neighbor's did from the Drake L4B?...(c;

Larry W4CSC
"POWER is our friend!" - (Robert, KD4PBC - paging engineer)
--
Message for Comcrap Internet Customers:
http://tinyurl.com/3ayl9c
Unlimited Service my ass.....(d^:)
..



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