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160 meter inverted L radials

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG4DYN, Jan 8, 2021.

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  1. WA9GON

    WA9GON Ham Member QRZ Page

    My 175-foot RG-213 coax and rotor cables are underground and bonded. I use a coax switch at the tower.
     
  2. W9XMT

    W9XMT Ham Member QRZ Page

    Below is what I think I understand from the details about the inverted L system with a top-loaded, vertical re-radiator 15 feet away from it.

    I don't have accurate information about the HF beams, so I just added some structures generally matching the descriptions I saw here.

    The wires leading down from the 4-wire counterpoise below the feedpoint of the inverted L are there to include common-mode radiation on the coax feedline as it exits the ground plane (Earth), plus the connection of its shield OD to an 8' buried ground rod, at that point.

    The elevation angle for the gain plots was chosen to favor those more suitable for DX work. Gains are quite a bit higher than shown there, for greater elevation angles.

    Radiation resistance at the feedpoint terminals is ~ 3.2 Ω. The NEC model AGT is 0.993 (nearly perfect).

    [​IMG]
     
    Last edited: Jan 22, 2021
  3. WA9GON

    WA9GON Ham Member QRZ Page

    Thank you, Richard. I did not give you accurate information. The base of my antenna is 15 feet away from my tower and about 3 feet away from the tower at the bend. The HF beams are both Optibeam products; model OBLY 14-5 ( 20-10 meters and model OB4030 ( 40-30 meters ). You do not have to model anymore for me. I appreciate your effort. Gerry, WA9GON
     
  4. W9XMT

    W9XMT Ham Member QRZ Page

    Ok, Gerry. Thanks for your appreciation, and hope the graphic gave some understanding of what effects your nearby tower and beams (as installed) can have on the performance of an inverted L antenna.
     
  5. WA9GON

    WA9GON Ham Member QRZ Page

    One option I am thinking of using an inverted L antenna for 80 M or 160 M and have the tower support the far end of the inverted L horizontal wire. Any thoughts?

    Gerry, WA9GON
     
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    Sounds like this would be an inverted-L where the horizontal part slopes up toward the tower?

    How high could you put the vertical-to-horizontal corner?

    Can you elevate the radials at least so you can walk under them without touching them?
     
  7. WA9GON

    WA9GON Ham Member QRZ Page

    I am thinking of buying a fiberglass pole ( nested ) that goes up 40-50 feet. With radials at 8-10 feet off the earth, that would leave me with 30-40 feet vertical.

    Gerry, WA9GON
     
  8. WA9GON

    WA9GON Ham Member QRZ Page

    What length changes would there be for the frequency of 3.550?

    Gerry, WA9GON
     

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