[RFI] Power Line Noise
Michael Martin, RFI Services
mike at rfiservices.com
Thu Apr 16 18:22:21 EDT 2020
That's a good find Scott, especially if you get it repaired and find that you're correct.
The results of your investigation and the symptoms you followed to find the result are not uncommon at all. It's very common for HF directional antennas to be inaccurate when looking atsources that close to your antenna. That's a daily occurrence for me. As far as the polarization is concerned oh, I'm betting when you go back out there tomorrow to check out what I'm telling you you'll find that as you approach the source your antenna will be polarized more diagonally with the closer to the source you get. I use 143 megahertz 95% of the time and if my noise is strongest when my antenna is horizontal I know I've got further to go, not that I wouldn't do it otherwise.
using a small portable oscilloscope along with that receiver would enable you to see if both of those are wrestlers are creating noise. the oscilloscope will allow you to see you all the noise is affecting your antenna not just the one you're closest to the height of the oscillations on the scope will determine the strength of the signal coming in.
Has Jim replied to your post, his scenario is also common. However each investigation is different and can bring different results. The noise sources that are closer to you are more elusive to an HF beam. The noise is radiates from the pole and wavelength matching whatever frequency you're using to receive the noise. so if a noise source radiates from the pole and arrives at your antenna at the peak of the wavelength you get a very strong signal. If it arrives at your antenna at a null in the wavelength, that noise source can be very weak and sometimes so weak you don't even receive it.
When I'm investigating noise it's affecting HF and I swing a being around and it gives me for example, a northern direction, I go outside I hold my 143 antenna and I do a search and I see if I see the same noise pattern from the qth. If I do I walk to it. If I don't I get in my truck and I go in the direction of the beam heading and I go everywhere the power lines cross that beam heading and look for wherever than antenna is receiving the signal from.
I would urge you to keep in mind that the lesson learned isn't what you're going to see every time it's going to change depending on the source the hardware around it and how far away it is as well as how it gets to your antenna.
If I were you oh, I would report it to the parent company tell them about the two arrested as you have noise on has a suggestion. I would not tell them that is my noise I would let them make that determination. It isn't likely that you have to causing your noise problem and it may not be the arrest you at all. The mfj or Homebrew ultrasound devices are not extremely sensitive and have a hard time picking up noise sources that are blocked or covered up with something. Meaning, it's very uncommon for them to detect I like me arrested that's bad unless it's blown open and is split so the ark is exposed. what you normally find them picking out is Corona off of pin type Brown insulators. That's extremely common, but is not the source of your noise.
Corona is almost never the source of your noise but is a result of arcing. It's very common to have several Corona sources on a structure and none of them be your noise as common as it is to not be able to detect the noise with the ultrasound receivers that are not very high quality.
I apologize for any typos for I'm using voice to text so I can do this quicker and I don't have time to proofread.
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On Apr 16, 2020, 5:32 PM, at 5:32 PM, K9MA <k9ma at sdellington.us> wrote:
>I think I just learned something interesting. I'm in the city,
>surrounded by 14 kV overhead lines. I went out today to track down a
>noise source, which on the HF bands appears to be coming from the east.
>What I found, with a VHF tracker and an ultrasound tracker, is that it
>appears to be coming from two lightning arrestors across the street to
>the NORTH. (The ultrasonic tracker points to one particular arrestor
>each of two different poles.) So why does it seem to be from the east
>HF? (Yes, I'm absolutely sure it's the right source.)
>It has to be the polarization. My tribander is, of course, horizontally
>polarized, so it's most sensitive to vertical polarization off the
>But, something I never realized before, one should expect line noise to
>be mostly vertically polarized. The current from an arcing device like
>lightning arrestor flows in BOTH directions away from the source on the
>horizontal lines, so the horizontal component largely cancels out. It's
>like the top of a "T" antenna. The radiation then mostly comes from the
>vertical ground wire.
>Generally, I've found the HF beam heading to be pretty accurate for
>distant sources, perhaps because the vertical component is attenuated
>more quickly. With the VHF tracker (135 MHz), I do find I have to
>sometimes turn it vertically, but not consistently up close. I expect
>the shorter wavelength has something to do with that.
>In any case, the moral of the story is don't just look in the direction
>your HF beam thinks it's coming from!
>k9ma at sdellington.us
>RFI mailing list
>RFI at contesting.com
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