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Author Topic: A line noise problem resolved  (Read 247 times)

K8AC

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A line noise problem resolved
« on: December 21, 2022, 12:21:13 PM »

For the past many months, I had a noise problem on 10, 12 and 15 meters that grew increasingly worse over time.  After I eliminated potential noise sources in the house, I noticed that the noise disappeared when it rained and always came back after a day of dry weather.  So, I figured it was likely a nearby line problem.  The noise as heard on a receiver didn't have a 60 Hz component, but rather sounded like something frying in a skillet.  And the intensity varied quite a bit across the 10 meter band, with a distinct null appearing every 100 kHz or so.  I had also used a portable radio tuned to 28 mHz and held it up to the ground wire coming down the pole on several poles on the street and the noise increased substantially as the radio approached the ground wires. 

I reported the problem to the local power co-op and they showed up today to check out the line hardware.  They found a defective lightning arrestor about 200 yards down the road and replacing it was just a 5 minute job.  They brought the defective arrestor to me and explained the problem.  The arrestor had a ceramic body, maybe 4" in diameter and 15-18 inches long.  The unit had several cracks over that length.  These units had been sourced from China and the guy said they'd had a lot of similar failures with them.  He then showed me what they replaced it with and the new arrestors had a polymer body with the consistency of rubber and no ceramic material.  When I checked the bands, the noise was completely gone.

If you ever have a line noise problem like this, it is helpful if you can do anything to help pinpoint the problem (beam heading, etc.) and if you know if the problem disappears or is less when it rains.  The noise can propagate a long way down the line, so it can be difficult or impossible to pinpoint with your beam, but in my case there was a slight peak in the noise in the direction of the problem pole.  When contacting the power company, I started with their director of communications and he just happened to be studying for his ham license and so was sympathetic to the problem.

73, K8AC
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WB6TIX

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Re: A line noise problem resolved
« Reply #1 on: February 06, 2023, 09:07:11 PM »

Listening to the noise in the VHF and even UHF bands seems to offer better resolution of the source of the noise. 

I recently was able to track down a power line noise problem to a particular pole by using my Yaesu FT-60 tuned to 130MHz (easiest way to get the radio into AM mode).  I didn't even bother with a directional antenna....I just took the dog for a walk along the power line route while listening to the noise on the radio.

There is nothing magic about the FT-60.  Instead it's the frequency range and AM mode that is "important".  So, any portable VHF/UHF radio that can be put into AM or SSB mode will do the trick.

BTW, the dog was disappointed that I was able to quickly find the problem.  :-)

Eric
WB6TIX
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W1VT

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Re: A line noise problem resolved
« Reply #2 on: February 07, 2023, 05:25:45 AM »

AM on VHF/UHF is a common feature on handhelds made by the major manufacturers for hams.

But, I've never heard of any of the cheap Chinese imports offering AM on a VHF or UHF band. They seem to be FM only.
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