vertical antenna problem

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE4QCO, May 2, 2012.

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  1. KE4QCO

    KE4QCO Ham Member QRZ Page

    I have a A-99 for 10 meters, works well. I went to 80m with it, ( just recieve, no TX) done great utill I started to thread the pl 259, soon as the barrel touched the rigs so- 239, recive went to 25% of what it was with just the center of the pl 259. what caused this?? thanks don. ke4qco
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    The antenna is effectively a short circuit on 80m, by design.

    When using only the center pin of the coax, you're using all of the coax plus all of the antenna as a long wire antenna. As soon as you connect the outer conductor (connector shell), that "feature" goes away and the antenna is essentially a short circuit on the end of the coax.

    It was never designed to be used on 80m. Actually it was never designed to be used anywhere except 25-30 MHz.
  3. W9GB

    W9GB Ham Member QRZ Page

    Wavelength of the Radio Waves matter !!

    3.5 - 4.0 MHz or 80 meters .... the wavelength is EIGHT times (Longer) that of 28.0 - 30.0 MHz or 10 meters.
    The Audio analogy is :
    Trying to have a Soprano voice (A99, for 11/10 meter) sing the Bass musical line (80 meters) :).
    Don -

    Best 80 meter antenna (covers full 500 kHz) is 1/2 dipole with parallel elements 2-3 feet apart (fat dipole) .... that antenna is ~ 135 feet in length (a real estate problem for many).

    N3UJJ Antenna Project

    Shortened antennas for 80 meters (Verticals or Horizontal Dipoles) suffer from narrow bandwidths.
    Last edited: May 2, 2012
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