One Month of Phasing: What We Really Learned About RX Arrays

After a deep dive into phased RX arrays—across weeks of modeling, measuring, and testing—some truths have emerged that matter more than simulation plots and textbook theory. Whether you're building an EchoTriad (our 3-element trilateral system) or the QuadraTus (our 4-square phased array), understanding what really impacts your signal-to-noise ratio is key. Here’s what one month of obsessing over phasing taught us.

1. RDF Is Everything

Receiving Directivity Factor (RDF) is the true metric for how well an RX array performs. It’s not about peak gain, lobe angle, or even rear null depth. A higher RDF means more wanted signal, less noise — plain and simple. Aim for 8–10 dB or more.

2. Forget the Rear Null Obsession

Rear nulls may look great on paper, but in practice, they're narrow, frequency-dependent, and only useful if they align with real noise sources. Most of the time, focusing on rear nulls leads to chasing ghosts. RDF tells you far more about practical performance.

3. Optimal Spacing Isn’t Magic, It’s Math

Spacing governs lobe width, RDF, and pattern shape. Some spacings just work:

  • 0.139λ for triangular arrays (EchoTriad)
  • 0.20λ for square arrays (QuadraTus)
    These values emerged consistently from both NEC simulations and real-world tests.

4. Multiband Means Geometric Mean

Trying to use your array across bands? Don’t pick the spacing for one band and hope for the best. Use the geometric mean of the wavelengths. It balances RDF across your entire target range — especially for 160/80m or 160/40m combinations.

5. Fixed Hybrid Phasing Wins

Fixed 45° hybrids outperform frequency-specific delay lines when it comes to stability and multiband compatibility. They provide clean, broadband phase shifts that hold up across bands without detuning.

6. Low Mounting Still Yields Low Angles

You don’t need to mount your RX array at 20 meters height. The phase pattern has a greater impact on reception angle than elevation itself. An EchoTriad setup with three EchoTracers just 1.5 meters high already delivers excellent low-angle DX from 20 to 6 meters. For the low bands, a ground-mounted four of our VerticalVortex probes provides superior performance on the QuadraTus 

7. Common-Mode Rejection Is Not Optional

Poor CMR can bury a good RX design. Using isolated active elements and hybrid-fed systems improves inter-element isolation and reduces unwanted pickup from local sources.

8. Models Help, Reality Decides

Free-space and simplified phase models—especially with active, electrically small RX elements—can predict real-world behavior with surprising accuracy. However, they don’t account for coax loss, hybrid imperfections, terrain conductivity, or local noise sources. NEC adds some realism, but ultimately, field testing remains essential. It confirms assumptions, exposes practical limitations, and validates performance in your actual noise and ground environment.

Summary

If you want an RX array that really works, stop obsessing over deep nulls or textbook beamwidths. Focus on RDF. Use the geometric mean for multiband designs. Keep spacing in that 0.139–0.20λ sweet spot. Choose fixed hybrids.

And above all — trust your ears as much as your models.

That’s what one month of phasing taught us.

 

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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.