G4NSJ – Grounded loop aerial

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G4NSJ grounded loop aerial

This is my grounded loop aerial.

The red lines are the support poles. They’re not actually red in colour, but they’re support poles all the same. Paint them blue, if you want to. The height of the horizontal wire is about forty feet, plus or minus a bit. Again, controversy surrounds the length of the horizontal bit. Short? Long? More on that later.

The earth is a continuous length of 15mm copper pipe buried beneath the ground running from one end to the other with various radials and rods bonded to it. The aerial works on all bands, but I use it primarily on top band. There have been a thousand questions hurled around about this aerial… What does the horizontal section do? What does the vertical bit at the house end do? Should the earth physically (electrically) complete the loop?

HOW IT WORKS

The theory behind this aerial, as I understand it, is that the RF current is forced into the vertical section at the end of the garden. Why? Because the base of the vertical is grounded, it’s at ground potential, and therefore this must be the high current and low voltage point. The voltage at the base of the vertical section, with respect to earth, must be zero. The idea is that this works as a vertical aerial on all bands. Bear in mind that the high current section of an aerial is the high radiating point.

I’ve given the aerial a good thrashing on top band with excellent results. I am now going to thrash the thing of the five meg frequencies. So far, on receive at least, it’s every bit as good as my doublet.

The ATU is in the shack and the copper earth pipe is about 10 feet long running down from the window to the ground. The ground being that bit of mud at the base of the house. The ATU is shown below.