Rain "curing" raspy line noise

[K3PI]

I have been plagued by what sounds like line noise for weeks.  The power company came out checked the transformer, changed some insulators, etc.  Even pulled the power to the house but the buzzing interference continued.  My next move was to see if it was coming in via cable, phone lines, etc.

Today, after a steady downpour all day - the noise is gone.

These power guys are very cooperative but kinda clueless on how to troubleshoot this.  Where would you point them next based on the noise going away following a good soaking rain?

73
Russ K3Pi

[WA1RNE]

 After replacing the transformer, insulators, did the noise level decrease any degree?

 If you haven't already done so, get a portable AM/SW radio and try to pinpoint the general location of the noise.

 Passing this info on to the power company should make it worth their while to come out for a second look.  They've likely missed something, like another bad HV insulator, transformer bushing,  a poor connection or some other piece of faulty distribution equipment.


 ....WA1RNE

[KF7CG]

Do you live in a dusty environment? This sounds like a case of dust and conductive dirt build up on high tension transmission line insulators. The resultant leakage can generate significant noise at all frequencies. A good heavy rain or several days of rain can often wash enough of the dust of the insulators to cure the problem until the dust builds up again.

This can be a ongoing problem in some areas.

KF7CG

[K3PI]

Thanks for the replies, guys.

No the noise did not change any when the power crew did their work.  In fact, the noise was still present when the power was off at the pole.

I wouldn't say the environment is dusty, but the pollen has been terrible this year so I can imagine any and everything has a big build up on it.

I contacted the local phone company which is also provides cable tv and is one of two ISPs.  I contacted them before the rain, so when they showed up there was no noise.  However, they did say they found two pieces of competitors (ISP) equiptment on poles in the neighborhood with major leakage and went ahead and tightened up loose connections.  They seemed to have a much higher degree of technical expertise than the power company did.

So it's still kind of a mystery.


Russ K3Pi

[AF4O]

Check with your local power companies engineer and see if he can contact the power distributor and request a rfi location team to come out. Also request a bucket truck crew from the local power come out at same time which the rfi team will likely do anyways to fix as they find. Try to schedule on a day that the interference is present. And follow them around, its good education. This was a real break for me as my power company was like yours and did not have much rfi location experience.
The rfi team showed up with a van of equipment including 3 pieces. A shoulder mount variable frequency receiver with small log periodic to locate the pole, an ultrasonic handheld dish receiver to isolate to usually one component, and a ultrasonic stick mounted sniffer for the bucket truck guys to really pinpoint.
I was lucky in that i got a guy (and another younger fellow) at first with the rfi team that was about to retire (unlucky that he is now retired). He wasnt in much of a hurry and stayed 2 days and located -many- sources.
Also look at April 2006 QST for a build your own ultrasonic dish receiver and May 2007 for a antenna to go with your portable receiver and what type receiver to use and other info.
I have about got all the parts to build the ultrasonic and hope to locate a couple of aggravating intermittents popping up lately.
I would strongly suggest you have someone locate the source(s) instead of the hit and miss which might burn out your local power company and cause strained relations (been there done that so i know).
Lastly do searches on the web and do all the reading you can about the topic. Read the ARRL's RFI book and others. My experiences at http://bellsouthpwp.net/a/f/af4o/rfi.html

73
Chuck
AF4O

[AA4PB]

I highly recommend the "AC POWER INTERFERENCE HANDBOOK" by KB7KK for some very good insight.

Its available from the ARRL at http://www.arrl.org/catalog/index.php3?category=Interference%2FDF

[N1UK]

Take a look at this

http://www.arrl.org/tis/info/HTML/pwr-line-noise/

The pins between the insulators can arc and cause problems. The rain tends to conduct across the arc gap and quietens the line down.

The interference guy came out to see me and he used a fiberglass pole to wiggle components to try and isolate the bad parts. I have about 6 poles near my QTH that require attention. I hope they fix it soon


Mark N1UK G3ZZM

[K9TOA]

Hi. I had a similar RFI problem, such that would dissapprear when it rained and on cooler days. It would completely dissappear in the winter!
The local power company experts were baffled as well, their equipment was showing the problem, but after replacing just about everything they could replace, back it came in the summer.
It was affecting my neighbors TV's as well, and they obviously thought initially that my radios were the cause of all their problems. I decided to tackle this myself and purchased a small MFJ signal tracer and built myself a directional antenna to help find the problem.
Long story short, I found it after a few days of walking the street with headphones and this antenna.
The problem was in my next door neighbors doorbell transformer, which was located in the attic. It was heating up in the summer heat and buzzing. When it rained the transformer would cool and the RFI would go away, as it would in the winter months as well.
My neighbor had this transformer replaced, problem solved. Their gratitude was such that they(neighbors) sent me a "Thank You" card and a check for 100.00 to cover the cost of my equipment!
They are now very happy to have a Ham on the street!

[AF4O]

--- "Their gratitude was such that they(neighbors) sent me a "Thank You" card and a check for 100.00 to cover the cost of my equipment!
They are now very happy to have a Ham on the street!" ---

My gosh aren't you the lucky one! I have some neighbors that have threatened me and my wife when I was operating on 6 meters.
I invited them to call the FCC. That was a year or more ago and no more calls. One because i blocked their phone number :<)

They are trying to pick up over the air broadcast it appears with a gull wing camper antenna some 60 miles away and they think its my fault that they get 6 meter interference. Go figure.

I often wonder if they wonder why their reception is much better on that cheap gull wing than it use to be. Could be because i messed with the power co for years getting them to fix all the powerline rfi that was so strong at one time, it was even coming in on my tv and it was on cable!!

[K1CJS]

Did they check the splices in the incoming lines where they transition from the overhead feed cable to the cables that go into your weatherhead at your house?  

I had an experience where there was noise coming in from the street which would go away when it rained or was extremely humid.  (I guess it would be called 'misty'.)  When I pulled the house main it also stopped.  For 2 months I examined the wiring, wiggled the cabling on the house around the meter feed and the cables that entered the house.  I found it one dry evening when the sun had gone down, I noticed a bit of arcing at that splice point.

A call to the power company had a bucket truck down there that night--the linesman told me the splice was just about to fail, and after it was replaced the noise vanished.  None of the linesmen had checked that splice point before that night.

I guess it may be a case of too many minor things to check, but one of those 'minor things' turned out to be the problem.