40 m ½ dipole antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by OZ1LL, Jun 17, 2021.

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  1. OZ1LL

    OZ1LL Ham Member QRZ Page

    Hello out there i have a question about 40 m ½ dipole antenna about its distribution. I have made one with a bu-50 balun. and trim the wire so i have measured it with my nanoVNA and i get about 1.5 swr on the 40 meter band. My rig is a ts-830s. i have set my antenna up semi permanet not like its 100 % unfolded i know its not good but i dont receive any kind of signal sometimes a new radio station. it is so import that my antenna is 100 % unfolded to get some signal?

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  2. WA7ARK

    WA7ARK Ham Member QRZ Page


    Welcome to QRZ. Put the actual pictures up on QRZ; do not post links to where the pictures are stored unless they are stored on a public web site.

    Yes, an effective antenna has to have wires more-or-less stretched out. They can be bent, but not more than ~90 degrees. They can be "folded", but the spacing between the two parallel, folded-back conductors have to be spaced at least a 0.1wavelength. They cannot be folded back laying parallel with no spacing between them. Even folded, appropriately spaced wires are not as efficient (as an antenna) as non-folded wires.

    Here, yet again, is a case where a wire antenna may be "resonant" (have a feed-point impedance where jX ~= 0 Ohms) and have a "low Swr" (have a feed-point impedance where R ~= 50 Ohms or matches the coax impedance), yet not be an effective "radiator".
    Last edited: Jun 17, 2021

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