Building an Ultrasonic Arc Detector

Discussion in 'Homebrew and Kit Projects' started by N0TZU, Apr 18, 2018.

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  1. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I'm building an ultrasonic arc detector for locating power pole RFI. It's mostly per the design by W1TRC in the April 2006 QST, plus some additional notes by N0SS.

    I found a 12" aluminum parabolic dish for an acceptable price so I'm using it rather than the much more costly 18" size of the original. The dish will have a wider half-power beam width and a little less gain but should still be quite usable. The calculated beam width is about 1.75 degrees which is 11 inches at 30 feet.

    Today I got the transducer well mounted at the focal point and am using a camera tripod to hold the dish for testing. I set up an ultrasonic transmit transducer about 30 feet away driven with a signal generator to check alignment and beam width. The very strong received signal can be observed directly on a scope.

    The next phase is attaching a handle and providing a simple aiming sight, then on to the circuit construction.

    IMG_1867 (1).jpg
    N2EY and W0VRA like this.
  2. WZ7U

    WZ7U Subscriber QRZ Page

    Cool! Keep the unwashed masses appraised of your progress.
    N0TZU likes this.
  3. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    Looks great! Good job!
    N0TZU likes this.
  4. N7ZAL

    N7ZAL Ham Member QRZ Page

    Very interesting and curious what transducer you are using and the frequency response of it?
  5. W0VRA

    W0VRA Ham Member QRZ Page

    Very nice!

    It'd be kinda fun to add a mixer that would convert the ultrasonic to audible frequencies. Might be a way to impress friends. "See that pole over there? You can't hear it with your normal ears, but listen to the electricity leak with my special gizmo!"
    N0TZU likes this.
  6. K8ERV

    K8ERV Ham Member QRZ Page

    Don't forget the sledge hammer for whacking the pole.

    TOM K8ERV Montrose Colo
    WA7PRC and KK5JY like this.
  7. KK5JY

    KK5JY Ham Member QRZ Page

    Don't forget the yagi antenna for finding the pole in the first place. :)

    The ultrasonic devices are fine, but they aren't for just walking around a neighborhood and looking at random poles, searching for noise. I watched a representative from a major power company walk a line one day, and he walked right by a pole that was noisy, and he heard nothing on his ultrasonic receiver. I could hear it on my Arrow yagi just fine from the same location on the ground (and from considerable distance, too). Ultrasonic can hear with great precision (or so I'm told), but the usable range is very short, and there are many power-line-mounted noise sources that may never be audible on an ultrasonic receiver, no matter how close you get. E.g., a failed lightning arrestor that is arcing internally may generate near-zero external audio noise.

    The Arrow yagi is the best RFI-fighting tool I have ever seen. Even with just an HT connected, it goes right to the noisy pole, the first time, every time.
    K2XT, WA7PRC and N3AB like this.
  8. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Agreed. I have a yagi and use my handheld on AM receive to find poles, but wanted to have the capability to pinpoint hardware with ultrasonic. Especially because there are two closely spaced poles nearby that seem to have some RFI problems.

    I’m going to make a better yagi with a nice handle and place for the handheld when I get done with this project.
    WZ7U, WD0BCT and KK5JY like this.
  9. KL7AJ

    KL7AJ Ham Member QRZ Page

    Very nice. I have an unused 3' dish I've been thinking about using for a spy microphone. It's fun to listen to hooting owls and buzzing bugs with the things.
    N0TZU likes this.
  10. K8ERV

    K8ERV Ham Member QRZ Page

    Only you------

    TOM K8ERV Montrose Colo

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