Ground radial patterns for vertical antennas

I don’t have a small lot, for a suburban home. It is about an acre. However, my house sits almost directly in the center which makes placement of antennas slightly challenging. I have a very enjoyable 50ft tower about 20ft off the end of the house with a triband yagi and an inverted-V doublet hanging from a crossbar just below the top. This gives me 10m-80m coverage with two antennas. But the question looms: what about 160m?

I know I won’t be able to put up a full 1/4 wave 160m vertical (120+ feet). So my designs revolve around an inverted-L. I have a small landscaped island in the back yard about 20ft from the tower where I can install a base for an inverted-L, and use a PVC elbow joint on a support cord from the tower for the bend in the L. A tree at the other end of the yard can support the top end of the L with a pulley and weight to accommodate the wind. But, the problem then remains with the radials.

For any vertical the minimum recommended length of the radials is 1/10 wavelength. For 160m that ranges from 49.2ft to 54.67ft. Most people recommend 50ft so I’ll use that for sake of argument. From the proposed vertical base, I can easily do 50ft in two cardinal directions. The other two are limited to maybe 30ft. That’s not enough. And thus brings me to the “ah ha” moment I had while researching this:

This is brazen taken from this post by WB5YUZ over on QRZ:

You do know that the radials can be formed into a spiral or any other pattern, as long as they don’t overlap, right? There is a TIS I know of that uses a very short (in terms of wavelength) vertical and less than ten watts to transmit on the AM band. The FCC intended this type of station to be audible up and down a few miles of roadway, but this station can be heard twenty miles away, even after dark! (Obviously this means they are exceeding allowable field strength limits, but I bear them no ill-will, so I don’t want to identify the station.) I asked the station engineer why he thought the set-up worked so well and he said, “I use 120 full size 1/4 wave radials.” I asked him how he found the space to fit them all, and he said, “I laid them out in a spiral pattern.”

Just. Brilliant. In hindsight, it is also obvious.

I need to see how this will work in my yard.

Posted in Antennas

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