Ferrite Mix for 144 and 432 Mhz

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by K2WH, Apr 8, 2021.

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  1. K2WH

    K2WH Premium Subscriber QRZ Page

    Building 2 antennas, and want to add some ferrite on the coax cable at the antenna.

    What mix is good for that frequency ?

  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Mix 61 is likely best.
  3. K2WH

    K2WH Premium Subscriber QRZ Page

    Thanks, I knew you would respond.

  4. N7EKU

    N7EKU Ham Member QRZ Page

  5. KH6AQ

    KH6AQ Ham Member QRZ Page

    Type 31 and 61 look good for those bands.

    Here are EZNEC results for type 31 ferrite to fit LMR-400. I would use at least 6 cores slipped over the feedline at the antenna.


    EZNEC model
    Modeling a dipole with a resonant 146MHz, 1/4 wavelength of wire perpendicular to represent a worse case coax shield. The ferrite core impedance is 300 +j75 ohms. Cores are touching end-to-end. RF power is 100W CW.

    I would use at least two cores at 100W CW and four cores at 500W CW.

    1 ferrite core: ferrite dissipation 4.8W, 4.8W max core
    2 ferrite cores: ferrite dissipation 2.6W, 1.3W max core
    3 ferrite cores: ferrite dissipation 1.8W, 0.6W max core
    4 ferrite cores: ferrite dissipation 1.5W, 0.4W max core
    6 ferrite cores: ferrite dissipation 1.4W, 0.4W max core
  6. G0GSR

    G0GSR Ham Member QRZ Page

    Maybe, but for VHF (and above) bands, its easy to get any required inductance with an "air core".
    VHF/UHF baluns are easy to make without ferrites.

    HF "thinking" about VHF/UHF maybe?

    KP4SX likes this.

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