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Author Topic: 115KV Transmission Line  (Read 1087 times)

AI7CH

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115KV Transmission Line
« on: July 29, 2019, 04:50:24 PM »

My QTH is about 900 ft. from one of these things. Is there a way to tell if this is the cause of my noise problem or should I just assume it is, and grin and bear it?

At this time, the only bands I use are 20 & 40M, and the noise level on both seems to vary between S3 and S5, sometimes S6. Never lower. 40M I kind of expect to be a bit noisier, but 20M.... not so sure. I realize it could be just summer-time background noise, but at this point its really causing some grief.

I've tried turning off all other electronics in the house, and the only change was two birdies at 14.212 and 14.274 disappeared. I'm pretty sure these are coming from my Internet modem/switch, so there's not much I can do about them, but the overall background noise didn't change appreciably.

Any suggestions would be greatly appreciated.
Thx,
Bill
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W1VT

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RE: 115KV Transmission Line
« Reply #1 on: July 29, 2019, 05:48:17 PM »

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K0UA

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RE: 115KV Transmission Line
« Reply #2 on: July 30, 2019, 02:42:40 AM »

My QTH is about 900 ft. from one of these things. Is there a way to tell if this is the cause of my noise problem or should I just assume it is, and grin and bear it?

At this time, the only bands I use are 20 & 40M, and the noise level on both seems to vary between S3 and S5, sometimes S6. Never lower. 40M I kind of expect to be a bit noisier, but 20M.... not so sure. I realize it could be just summer-time background noise, but at this point its really causing some grief.

I've tried turning off all other electronics in the house, and the only change was two birdies at 14.212 and 14.274 disappeared. I'm pretty sure these are coming from my Internet modem/switch, so there's not much I can do about them, but the overall background noise didn't change appreciably.

Any suggestions would be greatly appreciated.
Thx,
Bill

It has been my experience that the larger high voltage cross country transmission lines are seldom a major cause of powerline noise. Usually it is local distribution lines. Are you sure it is powerline noise.  Can you post a youtube video with good audio showing us what it sounds like. What you are hearing MAY or MAY not be powerline noise. Your neighbors are often the culprits here with switch mode power supplys. Powerline noise has a more unique "buzz" signature.  As for you internet modem. Try some mix 31 large ferrites with as much of the cords from the device wound thru each one as you can manage.  These devices can usually be tamed.  As for the noise your neighbors make that is another matter.  If it is local powerline noise it depends on how responsive the local utility company is.  NOT to say your 115K transmission line could NOT be the problem but in all my years of living with one in the back yard, it was never the source, it was alway local distribution lines. YMMV
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73  James K0UA

W6QW

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RE: 115KV Transmission Line
« Reply #3 on: July 30, 2019, 07:36:33 PM »

Having lived about a thousand feet from a 120KV transmission line a number of years ago,  I will say that the potential for arc-fault RFI is large. This meant that my noise floor for 40M was a similar S6. Using a spectrum analyzer and infrared camera, I was able to demonstrate to the utility that they had both dirty insulator blocks and cracked insulators, both causing the noise problem. But the root problems were not just nearby. It ended that the utility ended up cleaning nearly eight miles of line and replaced two cracked insulator blocks. BTW, it was the same utility that caused the Paradise, CA fire through a failed transmission line. So, if it's the same utility, they may now be more receptive to investigating the problem. If you have access to an infrared camera or ultrasonic noise detector, you should be able to easily demonstrate the problem to the utility.
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WB4SPT

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RE: 115KV Transmission Line
« Reply #4 on: July 31, 2019, 05:27:10 AM »

Take a 14 year old person with you and walk the access road for a mile in both directions.   Those ears will do 20kHz and might find ur issue. 
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N8EKT

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RE: 115KV Transmission Line
« Reply #5 on: August 25, 2019, 07:27:45 PM »

Having lived within 50 feet of similar lines i can say for certain that micro arcing of insulators is very likely.
If for example it gets worse during a dry stretch then clears up after a good rain, it is likely micro arcing. i had heavy electrical noise all the way into high vhf frequencies at times.
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