VerticalVortex2 — Technical Overview
Updated: 2025-09-05
The VerticalVortex2 is RF.Guru’s flagship ground-mounted active E-probe for serious low-band reception on 160 m, 80 m, 60 m, and 40 m. A 6 m aluminum probe couples the vertical E-field, and a high-linearity amplifier with fast TX protection keeps the front end calm next to QRO transmitters.
Purpose-Built for Low-Band RX
- Engineered for QRO-safe operation near strong transmitters.
- Clean, stable gain over the practical 1.7–30 MHz span AC coupling and a broadband LF/MW notch set the lower edge.
- Low noise pickup when installed with proper reference and a common-mode choke at the shack end.
Technical Overview
Signal Path (schematic-validated, general terms)
- Probe & Input Conditioning: The 6 m E-probe is AC-coupled into a small-signal choke with a low-pass section to reduce out-of-band energy and improve strong-signal margin.
- Layered Protection: Surge arrestor → low-capacitance ESD diodes → RF clamp diodes → transient suppressor. This stack shields the LNA against QRO fields and static discharges.
- Broadband LF/MW Notch: Centered at ~1.46 MHz with a low-Q response, attenuating ~0.8–2.1 MHz. This prevents MW broadcast overload while keeping HF intact.
- FM Broadcast Notch: Suppresses ~118–142 MHz to eliminate FM ingress, before the LNA and the main output low-pass filter.
- TX Detection & Hard Short: A tuned RF detector drives a precision comparator and transistor, energizing a miniature RF relay. On TX, the input is hard-shorted to ground.
- High-Linearity Gain Stage: A low-noise MMIC LNA amplifier with input/output pads for gain distribution and IP3 optimization.
- Output Cleanup & Interface: Post-amp LC section into a 30 MHz low-pass filter, then to a 75 Ω F-type output with bias-T powering over coax.
Performance Highlights
| Parameter | Value |
|---|---|
| Frequency Range (–3 dB) | 1.7–30 MHz with ~1.46 MHz broadband notch |
| Optimal Bands | 160 m, 80 m, 60 m, 40 m |
| RX Polarization | Vertical (E-field) |
| Noise Figure @ 10 MHz | <1 dB |
| Output IP3 | ~+36 dBm |
| P1dB (at output) | ~+18 dBm |
| TX Sense to Relay Drive | <10 µs detection; ~3–6 ms relay operate |
| Relay Recovery | ~2–4 ms typical fast return after PTT release |
| Current Draw (RX) | 120–180 mA @ 13.8 V relay current only during TX mute |
| Output Impedance | 75 Ω (F-type) |
| Operating Temp | –20 °C to +50 °C |
| Effective Peak Elevation Response | 160 m ≈ 14° | 80 m ≈ 13° | 60 m ≈ 11° | 40 m ≈ 10° |
Radiation Patterns
Patterns shown are simplified models for clarity — see why we use simplified models and not NEC . Real-world results vary with soil, surroundings, and installation.
Maintenance Tip – Corrosion-Proof Connections
For the aluminum probe base, junction hardware, and coax terminations, apply AL-1100 aluminum paste during installation. This prevents galvanic corrosion, maintains stable contact resistance, and ensures long-term durability outdoors.
How often? Apply once during install. In coastal or polluted areas, reapply every 2–3 years during inspection or when connections are re-opened.
For the aluminum probe base, junction hardware, and coax terminations, apply AL-1100 aluminum paste during installation. This prevents galvanic corrosion, maintains stable contact resistance, and ensures long-term durability outdoors.
How often? Apply once during install. In coastal or polluted areas, reapply every 2–3 years during inspection or when connections are re-opened.
Mini FAQ
- Q: Can it survive next to a kilowatt TX? — A: Yes. The input is hard-shorted during TX and backed by multi-layer protection.
- Q: Do I need radials or a ground screen? — A: No. VerticalVortex2 only needs a quiet reference. A ground peg with RC bleed and proper choking is best. On very poor soil, a few short wires (2–3 m) may be added as stabilizers, but large radials or bonding to big metal roofs usually increase noise pickup.
- Q: Will it cover LW/MW DX? — A: Usable, but below ~1.7 MHz the response rolls off by design.
- Q: Where to place the choke? — A: At the shack entry point, especially in noisy RFI locations.
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