Please note this article first appeared as a two part article in the January and
February 1998 edition of MARA NEWS
SOLVING LINE NOISE, PART 1:
David W. Bourque, WB1FLD
Those of you that have followed some of my past VHF contest summaries will remember last September's contest comments. I had line noise and more line noise. In reality I've had this line noise problem for about a year now. Like most troubles that are hard to find, this one was intermittent, never creating noise when I went looking for it or during the contest, until last September. It appeared and never went away. It was at this point in time where my adventure into Line Noise Hunting really begins. I hope you enjoy my multi-part article on this topic. I'll start Part 1 with some tips and follow this in part 2 with my experience.
Like most things in life, you need a starting point and some education. The first step is to ask others what they have done. The Internet was a great source for me. When asking questions on the Internet you (a) get some really good ideas, (b) some ideas that sound good, (c) some crazy ideas and (d) some that are not worth a cent. You decide on the value of each idea presented here.
The first step in solving your problem is to identify an area where noise is coming from. It could be right in your own home or miles away. First rule out your own home. If you can power your radio from a battery, turn off the Main power breaker to your house. If your noise goes away, good luck hunting in your house. Turn the Main breaker back on, then turn off one breaker at a time until you find the circuit, then the item.
If you need to hunt outside your home, a completely different set of possibilities exists. Ask yourself these questions. Does it appear at a regular time period in the day? If yes, it is most likely a business turning something on. Does it come and go with the weather? Goes away when it rains? If yes, it is most likely loose hardware on a power line.The remainder of this article will focus on finding this loose hardware.
Power line noise from loose hardware takes on many different forms. It can be a broken insulator, poor grounding at the pole, loose guy support hardware and many other things. Along with the different types of hardware problems you also have different voltages on different lines.
Chris, WB5ITT, a former Engineer in the field says the following. "20KV single phase or 34.5/35KV 3 phase will ARC more than 69KV OR voltages BELOW 20KV. I had more hell with the 20KV/34.5 KV systems than anything else...69 KV is high enough where it usually doesn't arc...it just BURNS!!! Voltages lower than 15KV don't seem to arc...they may buzz somewhat, but not that bad. 20KV ARCs and ANYTHING within a 12ft radius of the conductors WILL become charged and if near a ground, will arc!"
What does this mean for you? It means a lot when you're trying to find it. They also sound different into your radio. I'll add more to what Chris stated above. The BUZZ from below 15KV lines is usually heard a few blocks away. You'll find these problems in your back yard. The ARC from voltages above 15KV can be heard from miles away.
Before you go out hunting please keep this in mind. SAFETY! SAFETY!SAFETY! Now the hunting can begin.
Tip #1. Narrow your search area if at all possible. If you have a yagi antenna, try to define a search area or window. Do other hams hear the same noise that you do? If so, have them define an area where the noise seems to originate. Compare notes and define a smaller area and then begin your search. Standard Fox Hunting triangulation techniques work well here.
Tip #2. Use an old fashion AM broadcast receiver and tune down to one end of the band. Start walking or driving around the area you suspect and listen for changes in the noise on the radio. This is a good technique to find arcing and buzzing type of problems.
Tip #3. Pole whacking. If the noise is intermittent and your using Tip #2 above, you can walk along with a small sledge hammer and whack the bottom of a pole to see if the noise changes. Several folks on the Internet recommended this approach but... if any damage occurs from intentional "whacking" of the poles, yes, the power company CAN prosecute.I don't recommend this approach at all.Also, be prepared to explain yourself to the local law enforcement when they see you whacking a pole. Another approach that is similar is tugging on guy support wires to get things vibrating. Safety is a big concern with this approach. It is possible to have a guy support wire that is not making a good connection to ground at the lower end and it can be HOT!!!!.
Touching this wire or creating a vibration could cost you your life!
Remember, you're trying to find a problem with the power line. There could be a wire touching part of the guy-support hardware. When you touch it you provide a path for electric current to flow. Remember what Chris stated above; "Anything within a 12ft radius of the conductors WILL become charged and if near a ground, will arc!!!".
If the problem is loose hardware on the guy support and the tugging causes the ground to go away, you suddenly have the potential for a live wire from an ARC. Be extremely careful.
Tip #4. If you have a video camera with a low lux rating you can use it to identify some line noise problems of the arcing variety. You see, these cameras have the ability to detect IR signals. To test this point your TV remote into the camera and record some tape. Play it back and you should be able to detect the IR light from the remote. If this works, you can use it to your advantage. It turns out that some types of line noise sources will generate an IR signature. You can take your video camera out and drive or walk along a path you think is your noise source. Play the tape back later and look for it. It's best to do this at night. You're looking for loose hardware and the area may be extremely small. Take your time and pan the camera slowly at each pole.
Tip #5. Ron, W4FP, "Go back when it's dark and, using a good pair of binoculars, carefully scan over all the hardware, including mainline splices and tie wires, for signs of arcing ... you'll see it very well .."
That concludes my short list of tips to get you started on hunting for your line noise problem. There are many others but article space prohibits listing them all.
Well, as promised, here is Part 2 in my mini-series on Power Line noise. As you recall, Part 1 talked briefly about how to identify noise sources specifically from loose hardware. In Part 2 Ill share my actually experiences. I hope you enjoy it.
Since moving to New Hampshire back in 1989 my interest really swung toward VHF/UHF work. I finally get the real estate to put up some decent HF antennas and what do I do, go way up the bands. I moved into a location directly across the street from some high tension lines. I was warned by several that I would have lots of power line noise and my effective radio days were over. Not so as I learned. Those lines are as quite as can be. About two years ago I started having a gradual increase in my noise floor on both 6m and 2m. The increase was in one direction and not always present. During the VHF contests I seldom had a problem with increased noise floor until this past September. During that contest we had the worst noise problem. We could only work the strong stations and my outboard DSP unit didnt get rid of it all. As a result my score was low and my frustration high. Not a good balance. I had been ware of this problem for a while, it was just never a pain in the you know where.
Step 1, triangulation. Not every ham has the ability to tune VHF bands with an AM/SSB receiver. Remember, FM wont detect it. Finding hams to help became a problem. I finally managed to get one other ham that could hear the noise and he had a beam. Using his data point and mine I defined a very large geographic area to search. The area was 2 miles away from the house. Not up the street. Some of you may be asking, why didnt you use HF to collect more data. I couldnt hear the problem on my HF station and I didnt want to introduce possible irrelevant data from others.
Step 2, drive the area. Using my AM radio in the vehicle I tuned to 530 on the dial. No stations there that I could hear. I started driving this large geographic area. Under every pole and every wire the noise changed. Was it my noise? No, the noise I heard on 2m had a unique pattern to it. You could even watch it on the S-Meter. What I heard under every pole and wire didnt match what I was hearing on my AM radio. So I thought.
My frustration is building even more. Ive been over the area time and time again. Finding nothing.
Step 3, put the 2m all mode in the vehicle. I started lugging my 2m all mode around with me in the vehicle. I dont know about you but I was scared to death about leaving my heavily modified (extensive receiver front end rebuild) $1,000 radio sitting on the seat of my vehicle. Would it get stolen, slide off into the dash . I was nervous and getting very tired of dragging it in and out. Several more weekends and weekday nights and nothing. More frustration. The noise was also intermittent adding to my delays. Id have time to go look for it and it wasnt there. It would appear and I wouldnt have time. I started looking in September and we are now in November and Im no closer. What next?
I got into the habit of changing my radio to AM 530 anytime I got anywhere close to the area. Basically anytime I wasnt on the hiway. Wouldnt you know it. One evening Im on this street I had driven hundreds of times. I slow down for a vehicle making a U-turn in front of me. What do I hear? My noise. Same pattern. Could it be? I found a side street and turned around and parked it under that pole. Sure enough, that was it. Why couldnt I find this before? Turns out if you drive past this pole at normal driving speed you dont get enough of the signature to identify it. It sounds just like any other pole. I could also only hear it directly next to the pole. Wow, did I find it? Back into the vehicle with the 2m all mode. Again, parked under the pole I could hear it. Yes, this was it. Puzzling thing though. It was S7 at home but barely S2 under the pole. What gives? Horizontal versus Vertical polarization? Antenna gain? Who knows. I was expecting it to be much stronger so close.
Step 4, contact the utility company. I actually had a problem on my hands. What company do I call and who do I call at that company. Where I live we are on the border of two companies. New Hampshire Electric Cooperative and Public Service of New Hampshire. Which one had responsibility for this pole. After a few phone calls to some locals I discovered it was PSNH. I even managed to get the name and direct dial number of an Engineer that has experience with this type of problem.
After several minutes of questions centered around how I determined this particular spot he agreed to look at it. I also learned this gentleman is a licensed but in-active ham. Wow, a person that understood my problem. He agreed to examine the area. He has special equipment and it is portable so he can identify the problem much better then I. Great, this is exactly what I was looking for. He promised to call back the next day with his findings. Next afternoon he calls back. I wasnt exact in my identification. I was off by about 50 yards. The problem was inside a power sub-station a few poles into the woods from where I said it was. Inside the fence. No way I could have gotten any closer without getting inside the fence. He confirmed it was very strong RF energy and it was centered around 300 Mhz. He would put in the work order and it should be fixed within 10 working days. Well, the 10 days has turned into 2 months. When we finally found the problem we were already into December. Delays for the holidays, our northern friends get into trouble with ice, then ice in my back yard with neighbors having no electricity and Im patiently still waiting. Given all the service the crews must be doing Ill gladly wait for my turn. The January contest came and went and we struggled again through the noise. Low score again. Im still being patient but at least I know we have found it. One question lingers, did I find the ONLY source?
If you have a power line noise problem be patient. Go slowly. I learned about the video camera trick after the fact. Sure wish I knew about that one earlier. I hope you have found these 2 parts of interest. Id love to hear from you if you have any experience finding power line noise. We can all learn from each other.