Spatial Phasing, Not Just Delay Lines, Why RF.Guru builds RX Arrays with Fixed Hybrids
Broadband Hybrids vs Delay Lines: Phasing in the 21st Century
For decades, phasing in HF receive arrays followed the example set by legends like ON4UN: delay lines calculated for a specific band, empirically tuned for deep nulls and directional behavior. It worked, but came with inherent complexity — especially when aiming for multiband coverage.
The rise of broadband fixed-phase hybrids marks a pivotal shift. Instead of manually cutting delay lines and managing switch matrices, operators now rely on stable, frequency-independent phase angles — like 22.5° or 45°. This flips the design paradigm:
In classic systems:
- Delay was tuned per band
- Spacing was assumed (e.g., 1/4 λ, 1/8 λ, or 1/16 λ)
In hybrid-based systems:
- Phase is fixed
- Spacing becomes the tuning element
This subtle shift leads to a powerful insight:
You can now optimize your array by selecting spacing that matches your fixed hybrid angle for a given band, band pair — or even three bands at higher frequencies.
Rather than being constrained to traditional λ-based spacing assumptions, you use a calculator or spacing tool to determine where spatial phase offset naturally aligns with your hybrid. The result: clean cardioid patterns and strong RDF over multiple bands, without relays or active switching.
A Tool-Driven Approach
We are building a design tool that inverts the ON4UN model. Instead of calculating delay for a given spacing, it determines optimal spacing for your fixed hybrid.
- Input: Desired band (or band group), hybrid angle (e.g., 22.5° or 45°), layout geometry (e.g., equilateral)
- Output: Optimal element spacing in meters for best directivity/null position
We are currently focused on equilateral 3-pole arrays — a simpler geometry that offers clear benefits in RDF and directionality. A working solution is nearby and will soon be ready for public use.
This approach doesn’t replace ON4UN's wisdom. It builds on it — but now with broadband components and modern expectations:
- Simpler implementation
- Multiband performance
- No mechanical switching
And soon, the same logic will apply to:
- 4-square systems
- Phased beverage arrays
The core principle remains:
Fix the phase. Let spacing do the work.
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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.