Why the VerticalVortex Excels at Low-Angle DX Reception (But Not NVIS)
It’s a Vertical – and Verticals Don’t Do NVIS
The VerticalVortex is a vertical antenna, and as such:
- It has maximum sensitivity at low elevation angles, close to the horizon.
- It has very poor sensitivity straight up (high elevation angles).
This is the exact opposite of what you need for NVIS (Near Vertical Incidence Skywave), which relies on:
-
Radiating and receiving nearly straight up, so the signal reflects back down to Earth within ~500 km.
So:
- Bad for NVIS: The VerticalVortex has a deep null overhead, meaning high-angle signals (like local skywave) are strongly attenuated.
- Good for DX: It picks up the low-angle signals that travel long distances via shallow skywave hops.
Low Angle = Long Distance
On 160 and 80 meters:
- DX signals arrive at 5° to 20° elevation, especially at night when D-layer absorption drops.
- The VerticalVortex is optimized to listen in this low-angle range, rejecting local high-angle QRM and favoring distant signals.
This makes it especially useful for:
- DXing during greyline or night-time conditions
- Receiving weak transcontinental signals that NVIS-style antennas (like low dipoles) won’t hear well
RX Antenna Design Tailored to Propagation Mode
Most hams use NVIS antennas like low dipoles or loops for regional coverage on 80 m — which works great for traffic nets, ragchews, or emergency comms.
But if your goal is:
- DX contacts on Top Band (160 m) or 80 m
- Listening to weak signals from across continents or oceans
Then you need a receive antenna that favors low-angle arrival paths.
That’s exactly what the VerticalVortex does:
- Omnidirectional
- Low-noise
- Low-angle
- Perfect for 160/80 m DX reception
Summary
Use Case | Desired Elevation | VerticalVortex |
---|---|---|
NVIS | High angle (60–90°) | ❌ Poor (deep null) |
DX | Low angle (5–25°) | ✅ Excellent (peak gain) |
So while it’s not your best friend for local nets, the VerticalVortex is a DX hunter’s dream on 160 and 80 meters.
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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.