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Make A Quarter Wave Stub

Discussion in 'Amateur Radio News' started by W5JDX, Jan 14, 2023.

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  1. W5JDX

    W5JDX Ham Member QRZ Page

    George demonstrates how to cut a quarter wave stub to notch out interference. Emile packs for 2023 Winter Field Day. Mike explores W0CHP PiStar Dashboard.
    Plus, mysterious solar powered antennas installations are popping up. How could this be cryptocurrency miners?
    KK6QMS, AB1Q, W7XLR and 2 others like this.
  2. WA6Q

    WA6Q Ham Member QRZ Page

    George, thank you, nice presentation.
    73, WA6Q
    W5JDX likes this.
  3. ZL4IV

    ZL4IV Ham Member QRZ Page

    This was my favorite method of getting rid of interference in commercial installations. I though it had been forgotten.
    W5JDX and AB1Q like this.
  4. KD4FOV

    KD4FOV Ham Member QRZ Page

    No code techs trying to sound technical!! lol......
  5. KK6QMS

    KK6QMS XML Subscriber QRZ Page

    Interesting. So what are all the options for notching an offending signal? Filter cavities, tuned 1/4 wave stub, ....?
  6. WP2ASS

    WP2ASS Ham Member QRZ Page

    You have to find the correct place to put the stub in the feedline as well.

    I've seen plenty of stubs not do what they where supposed to do because they where located in the wrong position in the feedline from radio to antenna.

    Stub placement matters.

    WP2ASS / ex KD6VXI
    K3RW likes this.
  7. ZL4IV

    ZL4IV Ham Member QRZ Page

    Another trick is to have the coax slightly longer and put a small adjustable cap across the end and use that to notch out the offending signal.
    N7GWA and W5JDX like this.
  8. N7GWA

    N7GWA Ham Member QRZ Page

    out of curiosity, how would one go about doing this? Find an even spot in the feedline in accordance with the wavelength of the notched frequency, and place the stub at that location?
  9. W6KCS

    W6KCS Ham Member QRZ Page

    Yeah, I'm curious about this too, and the technical reasoning behind it.
  10. KJ7WT

    KJ7WT XML Subscriber QRZ Page

    I suppose a tiny VNA would do this, also? I'll have to drag mine out and see what it does.
    W5JDX likes this.
  11. WP2ASS

    WP2ASS Ham Member QRZ Page

    For those that are wondering about stubs and their placement.....

    The info written by Jim brown, K9YC will do a lot better job breaking it down than I will.

    WP2ASS / ex KD6VXI
  12. VK5KKS

    VK5KKS Ham Member QRZ Page

    I find cutting coax with a sharp chisel and block of wood gives a cleaner more accurate cut. I used a stub to stop two meters getting into the TV, worked a treat.

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