RFI from power line data transmissions

Given that almost every house has at least one computer, one TV and who knows how many CFL and LED lamps, yes, I would say there's plenty of junk on the power lines.

Switching power supplies which are the norm for most any equipment built for the last several years produce harmonic noise due to the non-linear loading of the power line.

A great example is when one of our traffic signals regularly malfunctioned.  The equipment was in good working condition and nothing obvious was happening to cause the problems.  An oscilloscope to monitor the power line showed harmonic noise on the power line whenever the problem occured.  The noise source was traced to a business using a 1400 horse power, DC motor on a batch mixer.  The AC/DC 3 phase power inverter was the culprit.

I started at the electric sub-station where I saw a 7200 volt primary load change instantly by over 200 amps repeatedly.  

Another traffic signal would go into flash every night at almost exactly 9 pm.  Again it was noise on the power line traced to a capacitor bank for power factor correction at a machine shop.  The capacitor bank automatically connects/disconnects by a timer.  A ferroresonant transformer had to be placed in the traffic cabinet to filter the power.

When you add up all the switching supplies in the houses on your secondary you can easily see how so much noise gets into your equipment.

AM radio is where all this noise ends up

Mark

Of three LED bulbs I purchased, one puts out a real RF blast on house radios.

I noticed on the spectrum analyzer the RFI from the bulb is many times worse down below medium wave on the long wave band.

Sometime I want to take a radio outside and see how far that noise is traveling in daytime and nighttime.

The bulb is in storage as an emergency backup if all the other bulbs go bad.

The labeling and receipts usually say these bulbs will be replaced if defective, but I can never keep track of where I bought the bulbs and how to find the specific paperwork.

This could be used in your FM improvement document....about the noise interference making AM unusable in a lot of locations.

Mark

I was going to take a walk outside Today and check my range.  I noticed a rise Today in power line noise compared with yeaterday's noise level.  Summer time is a lot worse and this will kill any range I could get for AM.  The noise is even in the SW bands as well.  This kills any effort to get real AM listeners for my station.  When the noise is low there is a chance of getting somewhere however.

but that could be due to our utilities being underground. Also, in my neighborhood there is one transformer for two homes which probably would isolate such signals.

Years ago I did some work at a power supplemental generating station and the did use RF over their lines for monitoring and control. Going by memory, I recall looking at the front panel of such a unit and the frequency was somewhere around 380 kHz.

An adjunct at my college had a day job at American Electric Power and told me that they are using fiber optic cables woven into the high tension lines for their data functions, at least on the very high voltage lines.

Neil Radio 8Z said, "fiber optic cables woven into the high tension lines for their data functions, at least on the very high voltage lines."

That is an entirely new concept to me, absolutely fascinating.

What about those smart meters they are putting on the sides of the homes now? That would emit some RF interference would it not? I was hoping that the transmitters in these things would not be as wide as a barn door. From what you guys are talking they may as well use a spark gap generator to transmit and we know how wide those old fashion things really are. Why would they even need such wide bandwidth for data? On another side note our lines here in Elizabeth City are up on poles. Hence all the AM noise.

http://www.arrl.org/smart-meters

As the document linked to by wcdx states, there is little chance of interference by Smart Meters, particularly in the AM band, as they operate in different frequencies, and under Part 15 rules.

I've experimented with Part 15 AM both in urban (Pitt Meadows) and in semi-rural (Bowen Island) environments, with both buried and overhead power lines, and haven't noticed much difference in the noise levels (or range).  I could even hear my Rangemaster signal in the parking lot of a major concrete shopping mall (quite clearly, actually, with some underlying static) in my car about 3/4 mile away from the transmitter.  That's not to say that noise in urban environments isn't a factor in range; I just don't think it's as major as it's being made out to be.

If you're only getting a few hundred feet range, I suspect that there is something else going on.  Don't forget that weak AM and FM signals will be heard much differently - an AM signal will start getting static introduced quite quickly, until it gradually fades away into the background noise, while an FM signal will remain quite clear and quiet until you hit the sensitivity threshold of the receiver (at which point noise will get introduced quickly and the signal will fade quite quickly as well).

I've had AM installations that only went a few feet, and some that went over a mile, with the same transmitter!  There are so many factors in the installation that I'd look there before blaming noise levels.

For about a year there was a terrible night noise on the extended band that started at a low level and rose to a very loud buzz every minute all night.

PhilB and others suggested it was a bad starter in a street lamp and I found it by driving around... a street light that kept trying to turn on with a pink glow that intensified and failed every minute.

I was planning on stopping in the daytime to get the pole number so I could report it, but by magic it got fixed and my AM noise is very low most of the time.

Something about the neighbors Christmas lights causes a buzz, but right now I don't hear it so maybe they changed something even though I see their lights are already up, I guess for Halloween.

As I drive around I monitor a blank X-band frequency and hear all kinds of buzzes and pops at various locations coming either from the poles or inside houses.

Another source of noise can be the MOV lightning arrestors on power poles.

Two IBOC stations persistently sludge up the AM dial with their sand-blasty racket.

I am wondering, if I record a station's IBOC buzz and re-transmit it on my station, will that be a copyright violation?

The buzz is mine. Don't steal my buzz.

I noticed L.E.D. signs are strong up to about 300 feet and it seems certain digital gas pumps are wiping out reception on sometimes both AM and FM.

I am on American Electric Power ( Ky Power ) out of Canton,Ohio and the noise from those lines is horrendous.