Hey everyone,
I’m working on a homebrew antenna project for the 10/11-meter bands (centered around 27.8 MHz) and want to get some feedback on a 3D loop concept I’ve been brainstorming.
The goal is to achieve 360-degree, horizontally polarized omnidirectional coverage with a low noise floor, but without the phasing nightmares, complex switching networks, or destructive mutual coupling that usually come with multi-antenna arrays.
The Concept:
Imagine taking a traditional bi-directional hourglass loop and turning it into a 3D cylindrical skeleton. I am planning an 8-facet (8 cross-sections) layout arranged evenly at 45-degree angles to form a cage.
To keep everything perfectly in phase, the entire structure will be woven out of a single, continuous unbroken wire.
The Dimensions & Geometry:
Build Constraints & Power Handling:
I will be feeding this antenna with a Ranger N4 running 400W+ PEP. Because of the high RF voltage, I’m planning the following:
Where I Need Help:
Before I start cutting heavy wire and building the frame, I would love some help from the software modelers here:
I’m working on a homebrew antenna project for the 10/11-meter bands (centered around 27.8 MHz) and want to get some feedback on a 3D loop concept I’ve been brainstorming.
The goal is to achieve 360-degree, horizontally polarized omnidirectional coverage with a low noise floor, but without the phasing nightmares, complex switching networks, or destructive mutual coupling that usually come with multi-antenna arrays.
The Concept:
Imagine taking a traditional bi-directional hourglass loop and turning it into a 3D cylindrical skeleton. I am planning an 8-facet (8 cross-sections) layout arranged evenly at 45-degree angles to form a cage.
To keep everything perfectly in phase, the entire structure will be woven out of a single, continuous unbroken wire.
The Dimensions & Geometry:
- Target Frequency: 27.8 MHz (λ ≈ 35.42 feet)
- Total Wire Length: Scaled to roughly 1λ (approx. 36 feet) or 2λ, depending on modeling.
- Structure: A non-conductive cylindrical frame (PVC/fiberglass) featuring 3 parallel rings (Top, Center "Waist", and Bottom).
- Transition Points: 24 nodes total (8 per ring).
- The Path: The wire starts at a bottom feed point, runs diagonally up to the center waist node, diagonally up to the top node, steps over horizontally to the next top node, and zigzags back down through the waist to the bottom. It repeats this around all 8 facets until the single wire closes back at the feed point.
Build Constraints & Power Handling:
I will be feeding this antenna with a Ranger N4 running 400W+ PEP. Because of the high RF voltage, I’m planning the following:
- Wire: 12 AWG or 10 AWG stranded copper to minimize skin-effect losses and broaden SWR bandwidth.
- Waist Isolation: At the 8 center crossing points, the wires absolutely cannot touch. I am designing a non-conductive center hub/spacer to maintain at least 0.5 to 1 inch of air gap to prevent high-voltage arcing.
- Impedance Matching: Because the parallel paths will drop the native impedance (likely down to 15–25 Ω), I plan to bypass lossy/meltable commercial baluns and use a rugged Quarter-Wave 75-Ohm Coaxial Transformer (RG-11) to step it up to a clean 50 Ω match.
Where I Need Help:
Before I start cutting heavy wire and building the frame, I would love some help from the software modelers here:
- Can anyone help me map this specific geometry in 4NEC2 or EZNEC?
- I want to see what the actual horizontal radiation pattern looks like, how uniform the 360-degree coverage is, and what the true native feed point impedance (Z) looks like at 27.8 MHz.
- Are there any obvious phase-cancellation traps in this specific single-wire weave that I might be overlooking?
