DeltaRex on a 65-Meter Rooftop: Turning a Loop into a DX Weapon
When the DeltaRex is installed 65 m above ground, it transforms from a compact multiband loop into a serious DX weapon. At this altitude, low-angle radiation improves dramatically, rivaling tall verticals in open fields.
Operating Bands and Modes
| Band | Functionality | Notes |
|---|---|---|
| 10–20 m | ✅ DX | Low-angle efficiency, good coverage |
| 30–40 m | ✅ DX/NVIS | Mixed lobes, tunable, low takeoff from height |
| 60–80 m | ⚠ NVIS | Usable with tuner, higher angles dominate |
| 160 m | ❌ Not supported | Loop too small |
Radiation Angles at 65 m Mounting
| Band | Est. Elevation Angle |
|---|---|
| 10 m | ~6° |
| 15 m | ~8° |
| 20 m | ~12° |
| 30 m | ~18° |
| 40 m | ~22° |
| 80 m | ~45° |
Why This Matters
- Low takeoff angles on DX bands
- Suppression of ground loss and clutter effects
- Clean, symmetrical azimuth patterns when roof-mounted centrally
Installation Tips
- Mount centrally on rooftop for symmetry
- Use a 1:1 choke ~4 m down coax to suppress CMC
- Avoid nearby metallic structures to preserve pattern
- ⚠ Guy arms in two directions for stability in rooftop winds
Summary
On a 65 m building, the DeltaRex delivers low takeoff angles from 40–10 m, with usable NVIS on 60/80 m. Compact, efficient, and unleashed at height, it becomes one of the best urban DX solutions where big verticals or radial farms aren’t possible.
DeltaRex on a rooftop: compact. elevated. unleashed.
Mini-FAQ
- Does height improve DeltaRex DX? — Yes. At 65 m AGL, low-angle DX performance matches tall verticals in open terrain.
- Is DeltaRex usable on 80 m from rooftop? — Yes, mainly for NVIS. Efficiency is lower but tunable.
- Why add a feedline choke? — To block common-mode currents and preserve the clean loop pattern.
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