A Switchable Parasitic Receive Array for Every Ham
Last updated: August 22, 2025.
Imagine steering your receive antenna in multiple directions, suppressing local noise, and pulling in weak DX—without trimming a wire or touching a tuner. That’s what a modern switchable parasitic receive array offers.
Why “High Q” Isn’t Always Your Friend
High-Q tuned parasitics look great in textbooks. In reality, they give razor-thin sweet spots that shift with soil moisture, frequency, or mast height. Our low-Q broadband approach—borrowed from ARDF—trades a few dB of ultimate F/B for stable patterns across bands and conditions.
Combining Passive and Active
The array uses a broadband active center element (e.g., EchoTracer) surrounded by four parasitic posts. The active element ensures clean low-noise signal delivery; the parasitics provide pattern shaping and directivity. Together, they yield consistent, contest-grade performance without retuning headaches.
Dual-Ring Geometry
Different bands require different electrical spacing. This design uses two concentric rings:
- Outer ring: 20 & 17 m — larger radius for longer wavelengths.
- Inner ring: 15, 12 & 10 m — tighter radius for higher bands.
This keeps spacing near ~0.17–0.20 λ across bands for predictable coupling and pattern stability.
Yes—but not TX-grade fields. Each parasitic just needs small floating radials (3–5 m), perimeter wires, or mesh. The key: consistent grounding across the ring for symmetry.
How the No-Tune Array Works
Four parasitics surround the active center in a square. Each has a small pre-set RLC load, switched by relays to act as a director, reflector, absorber, or invisible. Steering is instant and silent; in neutral state, the parasitics are isolated, leaving only the center active.
This scheme powers the EchoArray (20–10 m dual crown) and VortexArray (40 m crown). No re-tuning, no climbing, no fuss.
EchoTriad: fully active, six simultaneous beams, deepest nulls, maximum RDF.
Switchable parasitics: single active center + four relay-driven posts. Slightly less null depth, but simpler, cheaper, and close to EchoTriad in many real sites.
Why It Works Anywhere
- Pre-set components: Factory-tuned RLC loads for common soil/geometry—no on-site adjustments.
- Damped reactance: Series resistors broaden response, making arrays site-forgiving.
- Optimized spacing: Inner + outer crowns keep coupling consistent across HF bands.
- Latching relays: Zero power draw between switches; no noise from bias feeds.
Practical for Every Ham
No VNA, no hand-cut tuning. Place the posts, connect the controller, pick a direction. The system just works—in rain, snow, or sun. Think of it as an “HF beam for your receiver,” but broadband, low-Q, and push-button simple.
Mini-FAQ
- Do I need a controller? — Yes. EchoArray and VortexArray require a controller to set parasitic states. Phased arrays like EchoTriad and WaveQuad do not.
- How many directions? — Four primary (N/E/S/W) plus four diagonals with useful nulls.
- Can I use my existing active vertical? — Yes. EchoTracer or any high-CMRR active probe works as the center element.
- Do I need to tune for soil? — No. Damping resistors make the design broadly tolerant.
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