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Power-line noise

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Many amateurs whose reception is being impaired by faulty power lines feel that nothing can be done about it. However, W1FTX has found power-company officials most cooperative in eliminating the source of interference- with a little help from the ham and the right approach.

You need not "throw in the towel" when your location seems plagued with persistent power-line interference. The power companies have learned a great deal in recent years about the techniques of reducing undesired radiation from their lines, and with the cooperation of the amateur who is experiencing noise interference, they can usually correct any trouble within their responsibility quite effectively.

In several cases within the author's experience, line noises severe enough to wipe out the amateur bands entirely from 21 Mc. through 144 Mc. were promptly and (so far) permanently cured. All that was required was willing cooperation on the part of the amateur in making the work of the power company a little less time consuming. Without this cooperation it is doubtful that anything would have been accomplished.

Don't get tough

Put yourself in the position of the manager of the average small power company. He receives a complaint from an amateur conveying the general impression that "You've got a line noise somewhere near here that's wiping out half of the spectrum. Better get it fixed!" This is enough to add gray hairs to any manager's already thinning scalp. Noise-locating equipment is not always immediately available, especially to the smaller branch offices. It is expensive gear, and the company is usually forced to spread it rather thinly over the entire service area. In addition, it means diverting a trouble-shooting crew from other work for what might be an extended period.

Some of the sources of line noise are pretty tricky to locate. And then, of course, a fairly high percentage of the complaints will be found arising from sources outside of power-company responsibility, such as noise generated by equipment within a factory, hospital, or even a private home.

If, however, the manager gets a friendly call from an amateur stating that "I'm quite sure I've located a source of noise interference on or near pole number 276 on West Hill Road," the manager will be much more inclined to send someone out right away to investigate. From there on, relations will be good, and steps will be taken to eliminate the noise pronto. After all, a line noise means a loss of power, and the power companies are sharp enough to realize that they don't get paid for power leaks on their side of the meter!

How does the amateur find out that the noise that has been keeping him out of the DXCC is coming from a particular source? Well, it takes a little sleuthing, but it can be fun, once you get the hang of it. My own case is typical, and a brief rundown will give you some ideas to use in your own "Operation trackdown."

The trouble starts

We moved into what promised to be a really super location in September of last year. It's high on a hill with a clear shot in all directions, out in the woods where we knew we wouldn't be bothered by the racket from neon signs, auto ignition, welders, and other electrical devices commonly found only in the city. The OM could already hear the rare stuff rolling in as he signed that big fat mortgage note. It would be worth it!

Antennas were put up - an 80-meter halfwave for use on the low bands, and rotary beams atop a 40-foot tower for six and two meters. And the signals really did roll in - for a time. Then followed some revolting developments. It started in late October, when the weather began to get cool and crisp (meaning dry). A racket, best described as a high-pitched buzz saw coupled directly to the end of the antenna, started blanketing every ham band from 21 Mc. up. It was S9, plus enough to wipe out everything except the real rock crushers. If you're looking for DX, you don't usually want to work the loud ones. The weak ones just weren't there any more. Thinking that the XYL's refrigerator, or the oil burner, or something around the house had taken off on its own, a quick check was made of these and a few other obvious suspects, but nothing seemed out of whack inside the shack. After a few hours of impatient waiting for the noise to go away of its own accord, it was decided that maybe a little more scientific approach to the problem was in order.

Pin-pointing the sound

The six-meter beam was rotated, and it told us that the noise peaked up strongest when the beam was pointed southwest, or down the road from the house. The next step was to take the 2-meter mobile rig(1),(2) for a ride in that direction. With just a simple whip antenna on the receiver, the noise could be heard as soon as the car left the driveway. A cruise up and down the road showed that the noise had definite peaks and nulls - a standing-wave pattern of sorts. After several trips back and forth over the section of road where the peaks seemed loudest, one spot was found where the strongest peak of all occurred. Sure enough, it was right near one of the power company's poles. While listening on the receiver with the audio gain turned up full, the pole was tapped, first gently, and then a bit harder, with the head of an axe. (Don't let them catch you using the business end on their timber, boys!) As the pole vibrated from the blows, the noise became intermittent. Examination of the wires, insulators, and miscellaneous hardware at the top of the pole with field glasses disclosed nothing. It looked like any other pole; but it wasn't. It had an embossed aluminum - tag tacked to it bearing its own distinctive pole number.

Help arrives

At this point a phone call was placed to the office of the local power company. After a short discussion with their engineer, who seemed to be in complete sympathy with the situation, he agreed to send out a trouble shooter. This rosycheeked individual arrived at my home in due time, and asked if I was the one who had called to report some radio interference. He was invited into the shack to hear for himself. "Funny," he said, "I've never heard anything like that on the radio in the truck." Of course not. Power companies use f.m., but this fellow was no radio expert, so he didn't know about such things. I mention this just to forewarn you. You are the radio expert in this case, and don't be bashful about establishing this point. It will help you sell the job that is ahead of you.

A loose tie wire

The trouble shooter, after receiving a short course in ham radio, was then escorted, truck and all, to the scene of the suspected pole. With the audio gain on the mobile receiver opened up wide so that he could hear what was happening even when he climbed the pole, the trouble shooter (let's call him Jack, because he sure was nimble) donned his irons and went up the pole. He checked all the insulators, because any power-company man will tell you that leaking insulators are always the cause of this kind of trouble. But don't believe him - until he proves his point. Well, it wasn't insulators in this case. Finally, being somewhat of an experimenter himself, Jack began to poke around up there among the kilovolts. Sure enough, after a bit of prodding, shaking the pole, and banging on the crossarm, he heard the noise become intermittent, as I had. Further poking showed that the.cause of all this miserable racket was a short length of insulated wire used to tie the main distribution wire to one of the standoff insulators on top of the crossarm. They usually twist several turns around the main wire on either side of the insulator. The twists had loosened, and when the insulation was good and dry, corona discharge was taking place between the main wire and the tie wire. Jack snugged up the twists with his pliers, and the noise stopped.

We returned to the shack. He wanted to listen to the home receiver again to be sure. I could see that he was mentally scratching his head about it all, and he finally broke down and said, "First time I ever saw anything like that." Conversation with other power-company engineers indicates that not many of them are familiar with this type of noise source either, which is surprising but true.

Where there is one loose tie wire in a neighborhood there are almost always others, and this was certainly the case at my location. Before the winter was past, I had located the sources of no fewer than seven other noises, all being generated by loose tie wires. Seven times I called the power company, and seven times Jack, or his counterpart, came out to fix them. Another time we located a guy wire that was brushing up against a 4000-volt line as the lines swayed in a high wind. What a racket that one made!

Noise and the weather

There is more to this story. Noises of this sort disappear in wet weather almost with the first drops of rain, and reappear after the line has dried out. They come back gradually, intermit. tent at first, then increasing in frequency of repetition until they blend into a steady roar. They are at their worst on cold, dry, winter days, especially when it is windy. To locate them you sometimes have to cruise around in the chill winter blasts for a few hours until you can arrive ' at the scene of the offending source while the noise is present. Many times I have set out with the mobile receiver to return without having found the culprit. Upon returning to the home shack, I found that the noise had quit while I was in search of it. Yet on other occasions, the noise will persist for days, seeming to come from all directions with equal intensity. Don't let this fool you. It is probably coming from two or more sources at once, and the beam pattern of your rotary antenna just isn't sharp enough to pin any one of them down. You can be sure, however, that if you can hear the noise loud enough to bust up reception on your favorite band, it is probably being generated within a mile of your antenna. In rare instances, the source of the noise will be farther away than that, but in these cases, the noise is probably entering the receiver on the power line, rather than through the antenna. This is easy to check. Just disconnect the antenna, or if you're fussy, operate your receiver from an emergency supply independent of the company lines. If the noise is entering through the power line, the same general method of track own should be used. A directional antenna on the mobile receiver will be of great help, although it is not a must, and an S meter with which to plot the strength of the noise is also much better than an uncalibrated ear. About the only other equipment you will need is the aforementioned axe or, if you wish to avoid suspicion, use a sledge hammer, but with gentleness. A good sound whack on the pole will sometimes cause the noise to quit, temporarily, just as you are about to pin its source down!

I found the local power company most cooperative, and prompt attention was given to every complaint, especially after I had established my reputation with them as being right most of the time. Thus, it is important to be reasonably sure that you have found the real source of trouble before you yell for the power company's help.

Other sources

If they don't cooperate, and I'm sure this will be the rare exception, a friendly suggestion to the manager that he review the FCC's latest regulations on interference with any radio service will be certain to bring results in a hurry. Use this only as a last resort, however, and then only after you are doubly certain that the noise is coming from the power lines. Of course, there are many other possible sources of radio interference - including the following, to name some of the more common ones and their characteristic noises:

Commutator motors: High pitched, tearing.
Corona: Hissing.
Faulty insulators: Rasping, or buzzing.
Corroded hardware on pole: Staccato, irregular.
Loose hardware on pole: Popping.
Fluorescent lamps: High pitched and rough hum.
Traffic lights: Regular clicks or pops.
Ungrounded conductor with static discharge: Irregular bursts of low-pitched static.
Spark ignition: Sharp, regular, staccato.
Welding arc: Frying.

If your power company engineers seem a bit baffled by noise problems, as some of them may be, suggest that they get a copy of a report entitled, A Practical Handbook for Location and Prevention of Radio Interference from Overhead Power Lines.(3) This report was generated by a U. S. Naval Civil Engineering Research and Evaluation Laboratory, at Port Hueneme, California. It is dated 21 November 1956. Project NY 411-002-1, Technical Memorandum M-116. This report is available to industry through the Armed Services Technical Information Agency (ASTIR), Knott Building, Dayton 2, Ohio. It is a must for all power company engineering departments, although few of them seem to have heard of it. To my pleasure, one of the prime causes of interference, according to the report, is my old friend the loose tie wire!

Other points covered in this report will be of general interest. If the noise seems to peak a short distance either side of the point where a feed line, or junction, leads away from the line, with a null right at the junction, check the feed line, too. It may be the path to the source. The reason for the apparent null at the junction is the impedance discontinuity caused by the junction. Similar misleading observations can be obtained where a line comes to a dead end, and for the same reason. So if you come up against a few puzzlers, don't give up. The noise has to come from somewhere, and you'll find it if you persist.

Loose hardware

"Hardware" noises are also quite common, and these are apt to be the most difficult to pin down. It is no more difficult to locate the offending pole, however, than in the simpler case of the loose tie wire, and if it becomes necessary, the power company will replace everything on the pole until the culprit is found. It may be something as obscure as leakage between two lag bolts screwed into neighboring spots on the pole. If metal crossarm braces are used, the difference in potential between them can be appreciable, because they are in intense electric fields, as well as magnetic fields. If the two pieces are insulated from each other by a corrosion film, or a small air gap, an abrupt arc-over can occur one or more times on each half cycle, resulting in a pulse rich in harmonics that will cover large chunks of the radio spectrum. Depending on the dimensions of the pieces of hardware involved, they can act as efficient dipole antennas at certain frequencies, radiating a husky signal. Hardware interference is usually found when two pieces of hardware are not securely bonded to each other, or are not permanently separated by an air gap of at least 1½ inch, or a path along wood of at least 2 inch. This, however, is something for the power-company men to handle. The amateur's job is usually over once he has pointed the finger at the pole involved.

The real key to the rapid elimination of your line-noise problems is your own attitude. If you take a cooperative attitude, and really try to do an effective job of helping the power companies find the source, they will do their part, and the noise will be cleared up. If, however, you take a get-tough attitude and refuse to stir from your easy chair to help them, you may have a long wait until you can hear those weak, rare ones coming through again.


  1. Gonset Communicator.
  2. In the author's experience, car broadcast receivers have not been very effective in tracking down noise except in very obvious cases where the noise was extremely strong. Many types of interference, including the type discussed principally in this article, are bothersome only at frequencies higher than the 14 Mc band and often are not audible at all on lower frequencies.
  3. This publication has restricted circulation and may not be available to power companies except under certain circumstances.

Richard M. Smith, W1FTX.