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3.4kW DeltaRex - The Ultimate Low Angle DX Multiband Deltaloop
3.4kW DeltaRex - The Ultimate Low Angle DX Multiband Deltaloop
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The DeltaRex is a solid, base station-class multiband delta loop antenna designed for high-performance DX and NVIS operation from 40 m to 10 m, with usable coverage on 60 m and 80 m NVIS. Built for durability, the DeltaRex uses a heavy-duty triangular loop with a 120° bottom vertex and a dual-wire wide-top conductor on ~5 cm spacers to minimize RF loss and maximize long-term reliability.
The loop legs are constructed from 35 mm diameter, 2 mm wall marine-grade aluminum tubing, while the base and all mechanical fittings use 3 mm RVS316 stainless steel. Every metallic component is marine-grade, ensuring all-weather resilience.
Unlike portable loops, the DeltaRex is built for permanent installation. It is fed at the bottom vertex with an included 4:1 UNUN (rated 2.4 kW or 3.6 kW ICAS). A 1:1 current choke should be placed at ~4 m above ground (~0.05λ on the lowest band) to preserve balance and reduce common-mode noise.
Specs at a Glance
| Frequency coverage | 80–6 m (DX focus 40–10 m; NVIS usable on 80/60 m) |
| Feedpoint impedance | ~100–120 Ω (transformed to ~25–30 Ω via included 4:1 UNUN) |
| Power handling | 2.4 kW or 3.6 kW ICAS versions |
| Polarization | Horizontal |
| Choke recommendation | 1:1 current choke at ~4 m AGL (≈0.05λ of lowest band) |
| Footprint | ~11 m top span, ~22.4 m perimeter |
| Mechanical | 35 mm / 2 mm wall Al tubing; 3 mm RVS316 stainless base/fittings |
Operating Bands and Modes
| Band | Functionality | Notes |
|---|---|---|
| 10 m | ✅ DX | Efficient, low-angle radiation |
| 12 m | ✅ DX | Strong performance |
| 15 m | ✅ DX | Slight multi-lobe; may need tuner depending on height |
| 17 m | ✅ DX | Good radiation, wide match |
| 20 m | ✅ DX | Full-wave loop, strong DX |
| 30 m | ✅ DX/NVIS | Mixed pattern; typically tunable |
| 40 m | ✅ DX/NVIS | Efficient half-wave loop |
| 60 m | ⚠ NVIS | Usable with external tuner |
| 80 m | ⚠ NVIS | Sub-resonant, lower efficiency |
| 160 m | ❌ Not supported | Too short for practical use |
Recommended Mounting Heights
| Bottom Vertex Height | Top Wire Height | Best Bands | Radiation Angle Behavior |
|---|---|---|---|
| 0.5 m | ~5.5 m | 20–10 m | More regional short skip, easy install |
| 2 m | ~7 m | 40–10 m | Enhanced low angle, reduced ground loss |
| 3–4 m | ~8–9 m | 30–10 m | Ideal for DX + moderate NVIS |
| 5 m | ~10 m | 40 m & 30 m peak | Deeper DX angles, some NVIS reach |
Feed System and Choke Recommendation
Typical loop feed impedance is ~100–120 Ω, transformed by the included 4:1 UNUN to roughly ~25–30 Ω. Place a 1:1 current choke at approximately 4 m above ground level (≈ 0.05λ of the lowest band) to suppress common-mode current and preserve pattern symmetry.
Why Two Wires on the Top Span?
At first glance, the dual-wire top span might seem redundant, but it actually functions as a single, wider conductor. With ~5 cm spacing, the two parallel wires create a broader effective surface area, which lowers the loop’s Q and produces a broader, flatter SWR curve. That means more bandwidth, less sensitivity to weather and height changes, and a touch of extra efficiency versus a single thin wire. This is the same “pseudo‑cage” principle often used in premium HF elements.
For all bolts, screws, and electrical interfaces, apply AL-1100 aluminum paste during assembly to prevent galvanic corrosion and keep contact resistance low in outdoor exposure.
How often? One thorough application at installation is typically sufficient. In harsh coastal or polluted environments, reapply every 2–3 years during a visual inspection, or sooner if you open/retorque joints.
Construction Highlights
- Triangular 120° geometry for optimal loop current symmetry
- Loop legs: 35 mm / 2 mm wall marine-grade aluminum tubing
- Base plate & fittings: RVS316 stainless steel
- Dual-wire top conductor with ~5 cm spacers (≈11 m span)
- Total perimeter length: ~22.4 m
- Polarization: Horizontal
- Rugged, permanent-grade design
VSWR Sweep
Radiation Patterns
Patterns shown are simplified models for clarity — see why we use simplified models and not NEC. Real-world results vary with soil, height, and surroundings. These plots are for 3 m bottom height.
Comparison to Other Antennas
DeltaRex vs EFOC29:
More symmetry, lower ground coupling, better low-angle DX. The EFOC29 is lighter but more prone to common-mode issues.
DeltaRex vs IronWave6:
Far higher efficiency on 40/30 m, more gain on 20–10 m. IronWave6 is compact but tuner-reliant.
DeltaRex vs Vertx206:
Broader coverage and NVIS support. Vertx206 is a pure DX vertical on 20–6 m, less flexible overall.
DeltaRex vs TermiLoop (160–6 m):
DeltaRex prioritizes radiation efficiency and controlled patterns for DX on 40–10 m with horizontal polarization and lower ground coupling.
TermiLoop is a broadband terminated loop that delivers smooth < 3:1 SWR from 160–6 m in a smaller footprint, ideal for all-band convenience and constrained sites.
On 40–10 m, DeltaRex typically offers higher efficiency and stronger low-angle DX; on 160–80 m NVIS and general coverage, TermiLoop provides greater band reach with simple matching.
Summary
The DeltaRex is the ideal permanent multiband loop for operators who want reliable DX from 10–40 m with NVIS capability on 60/80 m, all in a rugged, corrosion-resistant triangular structure. No radials. No traps. No gimmicks — just performance by design.
Mini-FAQ
- Does the DeltaRex need radials? — No, it’s a closed loop.
- Do I need a tuner? — Usually not on 40–10 m with an internal ATU. 60 m and sometimes 15 m may need an external tuner depending on height.
- Why are there two wires on the top? — The dual-wire top acts as a single, wider conductor. The ~5 cm spacing lowers Q and broadens bandwidth, giving a flatter SWR curve and better stability than a single wire.
- Is it portable? — No. It’s engineered as a permanent installation antenna.
- Where should I place the choke? — At ~4 m above ground (≈ 0.05λ of the lowest band).
