Feedline lenght on EF Quad w/coax grd

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    KC4SR
    Member

    I’m getting ready to put up my new EF Quad in a permanent installation. All of my antenna cables come back to coax surge suppressors mounted on a copper flange installed on the ground rod at the shack entry point. That rod is bonded with #6 to one other station ground rod about 15 feet away and as per NEC, to the house electrical system rod about 25 feet away. The 100 watt rig is attached to 10 ft of coax coming into the house from the surge suppressor on the ground rod

    From the FAQ:
    “The only conditions where we were able to measure significant RF on the outer coaxial shield occurred when:

    The coaxial length was an odd multiple of va wavelength AND
    The rig was grounded.”

    I am interpreting “odd multiple of va wavelength” as odd multiple of 1/4 wavelength since these would be resonant, low impedance and would allow significant current flow. So you would want a length that is not resonant on any of the 4 bands between the antenna and the grounding point.

    This seems to be the only reasonable interpretation, but I just want to be clear before I start cutting coax and installing PL-259s. This antenna is a perfect fit for where it’s going, and a center fed would have been unacceptable there. I’m really looking forward to it.

    73, Ken

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