Here’s another interesting web site about Power-Line Noise: http://www.powerlinenoise.com/ I just found that one on 02/01/2010. I’ll check it out some more, note: The sound that you hear (turn your speakers on) is very much LIKE what I hear on my radio gear here. He has some videos up on this site of his Power Line Noise Tracking Sessions. It’s interesting to me, his use of the Arrow Antenna Yagi + small handheld ham rig with AM capability. (Time to start finding, tagging, and bagging some noisy power poles. I would at least like to tag and report those poles / hardware that cause noise that affect my Ham Shack (1.5Mhz to 53Mhz) but I have this funny feeling after watching videos on powerlinenoise.com that it will be more than one pole, in other words more than one interference source. At my location it has already proven to be up to a 2 count as of now.) Hey maybe we can start a new sport – similar to WiFi War Driving (which derives from the old War Dialing in the Telephone Modem days) and WiFi War Chalking. Yah you can get in for a couple hundred bucks or so. $60 for the Yagi antenna … Ham Radio guys probably already have the rig (note: it has to be capable of AM reception) because they often already have a dual-band handheld portable (handi-talky or walkie talkie) – but some scanners might even work for this, especially if the have some kind of S-Meter.
Anyway back to the original post that was here:
The powerline RFI that was located by FP&L when they came here awhile back (pulsing very strong RFI) seems to have gone away … but now it reveals what I think was the original RFI that I experienced before the stronger pulsing one came.
I may post more video showing how this sounds and where it is found soon. It still pretty much ruins my use of most of the HF/SSB Ham Bands (especially 3.8 Mhz and 7.175 – 7.300 Mhz ranges.) I wish FP&L would pay attention to me and solve this one as well. It’s very likely something else arcing AC high voltage somewhere on a power pole. It’s surprising that it doesn’t fry some of their own equipment or cause a fire somewhere. You almost want to say you wish it would burn itself out and fall down. But we wouldn’t want anyone to be hurt by falling powerlines or power distribution components. Somethings wrong… something shouldn’t be sizzling and pumping out RF signals that probably travel for miles (or further?)
Here’s W8JI on Powerline Noise: http://www.w8ji.com/power_line_noise.htm (Definately see it there with pictures! Nice info!)
Power line noise is generally a raspy buzz modulated at some low harmonic of the power line frequency. Power line noise is frequency insensitive, having only a very gradual change in level with frequency. Power line noise can be band specific, but it is never frequency specific. CB operators sometimes mistakenly call line noise land noise or ground noise, very unusual slang since neither the ground nor the land is a source of noise.
Power line noise is from the following causes, each of which has subtle but unique characteristics:
Pin or hardware arcs on insulators, generally bell insulators
Arcs from loose clamps or bolts that join wires
Arcs in hardware, like lightning arrestors
Arcs in hardware near, but not connected directly to, power lines
Poorly wrapped or insulated tie wires that secure power lines to knob insulators
Arcs inside equipment, like internal arcs in transformers or lightning arrestors
Insulator Pin or Hardware Arcs
This type of noise is a higher pitch raspy noise. It almost always goes away in wet weather. It also “breaks up” when the wires wiggle or move. When I did noise investigation for a few utility companies I would strike the suspected pole with a large hammer and listen for the noise to “break up”, or (after looking to see the guy wires were well clear of any hot lines) shake or push on the guy wires. You should not do this without permission of the pole owner. I had permission.
Insulator pin arcs are one of the most common sources of broadband noise on power lines. This noise is caused by low tension on bell insulators, allowing them to hang with visible sag or slack. The noise is generally a medium to low level noise with a higher sounding smoother pitch because the arc is weak with very low current, but like all noises it can propagate a long distance along the lines.
The pins on each end of insulators can be a common source of noise. The long insulator above is a newer Polymer type. It does not have the leakage capacitance of older ceramic bell insulators, and is not as noisy when span tension is low. The pins however are the same in almost all insulators. With low tension the pins corrode and make poor contact. This can cause a very tiny arc. The arc excites the power line through the insulator’s stray capacitance and the power line acts like a giant antenna. A few milliwatts of energy can radiate a long distance when using a long wire antenna like a power line!
The problem is rooted more in the capacitance of the insulator than actual leakage across the insulator surface, although both can be involved.
The longer polymer insulators on the pole above have a long fiberglass rod core and a very long external leakage path around the ribs. Ceramic bell insulators have a very large metal casting capping the low voltage or grounded end, and have an interlocked center pin and body cap separated by ceramic. Spacing is small and parallel surface areas are large in the more compact ceramic insulators, causing very high capacitance between the metal cap and the center pin of the ceramic insulator. The longer multi-ribbed polymer insulators have very low capacitance and a long leakage path, so they do not couple from end-to-end nearly as well as the ceramic bell insulators. A span might have to be left slack if the pole can not be back-guyed. Polymer insulators are preferred when a span has to be left slack.
Pins that secure the insulator to the hardware will corrode and build up a thin layer of insulation. When a span is slack (under low tension) the insulator metal end cap, the floating pin that locks the end cap to the eye bolt or mounting hardware, and the mounting hardware will arc across the thing layer of corrosion in the joints. This is because the pin is not pulled tightly against the mounting hardware and a small arc develops across the corrosion in the joint. In wet weather the arcing will often stop and the line become quiet. Slack spans with bell insulators are mostly a dry weather problem.
Loose Clamps and Hardware on Poles
Loose hardware on poles and wires is a common problem. It is also a safety issue! This type of problem generally makes a severe raspy strong noise over all bands. This type of noise is generally unaffected by moisture, although it can get get either louder or quieter in rain. If it is arcing from something being ungrounded, noise will generally go away in the rain. If it is a loose connection on a through connection, like a loose nut on the transformer primary connection, it will come and go, being largely independent of moisture.
All metallic hardware should be solidly bonded to the ground wire on the pole or it should be well-insulated from anything else. This is important for minimizing radio noise as well as protecting utility workers. It also reduces the chances of lightning damage.
The bracket above, for example, should be securely grounded to the ground wire running down the pole. Notice this utility let the bracket float. While that won’t make noise, it does create a hazard. If the disconnect switch insulator should ever arc through, develop leakage, or crack the bracket would become hot. If the ground wire was close but not touching the ground wire, it could arc from normal leakage and cause radio noise. It either needs to be a long ways away from the ground wire, or it needs to be bonded to the ground wire. Best would be to bond it into the ground wire.
The eyebolt holding the polymer insulator should also either be solidly grounded, or it should be kept away from the ground wire.
Hot clamps and other line hardware should be tight. Some of the most severe noise sources are loose hot clamps and corroded disconnect switches. Loose connections can actually start fires in dry weather.
(end quote. There must be a LOT of lose hardware hanging around on power poles. That stuff could fall down and injure someone. But then again people shouldn’t be walking around outside anyway… they should be inside writing a check to the power company 🙂 )
After all air travel is safe … your more likely to be injured or killed walking around and getting hit by powerline hardware, errr, I mean getting in a auto accident, than getting injured or killed in airline travel. That was a pun, intended 🙂
Power-Line Interference from: NR6CA http://www.nr6ca.org/powerline.html
As we all know, power lines are everywhere. Even in communities where power lines are laid underground, they are still above ground at some nearby location. Even with buried lines, transformer still abound in small bunkers dug into the ground and one of them may be right in front of your house. In addition, there are almost certainly street lights in your neighborhood that could also be a source of problems. And then we have traffic lights, internal home wiring just to mention a few other sources of potential power-line noise.
First you need to know that if, for example, your local power company has a problem near you that causes harmful interference, they are responsible for correcting it. They would clearly be in violation of FCC rules if they do not locate and correct the problem. From previous cases the FCC has gotten involved with a 30 day period to diagnose and repair seems acceptable to the FCC. The ARRL can also assist with these problems if it turns out the local power company is reluctant to diagnose and subsequently correct the problem.
Lower frequencies are more affected by power-line noise then VHF and above. If you have a potential power-line noise problem in your area it will most likely be fairly localized. That is not to say that a problem many miles from you can not be heard at your location. It only means that if you have a high noise level on 160, 80 or 40 meters (and even higher) that the source is fairly close by. Now a true FM radio will not be affected by this type of noise source since noise in amplitude modulated and not frequency modulated. Some modern radios though have both an active AM and an active FM detector working all the time. This is easier to do (read lower cost) for the manufacturer then designing in switching circuits that are selectable. What this means is you might have a wideband receive FM handheld transceiver (HT) that hears the noise. Rest assured it is the AM detector hearing it, not the FM detector.
So what causes power-line noise? Weather exposure is a major cause of problems. Dirt can build up across an insulator and then along comes some rain. Now all of a sudden there is a small arc across the insulator and 40 meters has an S9 noise level. You call the power company, they send out a technician on a nice dry day and he finds nothing. But then you say that it has been quite for the last few days. Sure enough, he leaves and a few days later along comes another rain storm and the noise is back. So if you pay attention to different conditions when the noise exists write them down and over time see if there is some correlation. If you have one of those nifty all mode, multiband handhelds (such as the Icom R-3), listen to the AM broadcast band in AM mode and start walking around the neighborhood. As you get closer to the source of the noise, it will get louder and stronger. You may even be able to pinpoint it to a specific power pole. Write down the power pole number from the power company label fastened to it.
Another common source of power-line noise is loose, cracked insulator or oxidized clamp, defective fuse and even a damaged lightning arrestor. These can all produce arcing across or within them that results in a very high HF noise level.
Not all power-line noise is limited to HF frequencies though this is where they are most common. It is rare to have power-line noise bother 2 meters or higher yet it does occur. Think about it, power-lines are very long, transformers are big and even the high voltage insulators can be massive. These things tend to generate noise at lower frequencies.
If you experience this type of interference, do yourself and favor, and the power company one as well and try to isolate the source as close as possible. Write down as much information specific to the time and conditions of the noise as you can. Don’t omit what may seem like an insignificant detail since that one small piece of the puzzle might potentially lead the power company technician to the actual source of the problem. But you do need to help yourself and go out and do some nosing around. Just NEVER, EVER, try climbing a power pole to get a “closer look.” It is not worth the risk. Leave that to the professionals. If you can narrow the noise source down to something like that pole or behind that fence, let the power company take it from there. You also need to be aware of any potential tresspassing. The power company has right-of-way in all locations where they have equipment, you don’t.
Alan Spicer – KA4UDX
Alan Spicer Telecom / Marine Telecom
communications (at) marinetelecom.net