VerticalVortex3 — Technical Overview
Updated: 2026-01-11
The VerticalVortex3 is RF.Guru’s ground‑mounted active E‑probe platform for serious low‑band reception on 160 m, 80 m, 60 m, and 40 m. A long vertical probe couples the vertical E‑field, while the receive front‑end is designed to be installed at the antenna (or at the start of a long feedline) for stable, predictable behaviour on the low bands and strong-signal resilience.
Purpose‑Built for Low‑Band RX
- Optimised low‑band behaviour: stable and predictable reception on 160 m / 80 m, with optional wider bandwidth settings when needed.
- Controlled HF roll‑off: selectable low‑pass shaping reduces out‑of‑band energy and helps keep receivers calm in dense RF environments.
- Robust front‑end protection: primary surge handling plus optional clamping/muting options for harsh real‑world installations.
- Feedline‑friendly interface: defined output termination for long coax runs (default 75 Ω, optional 50 Ω) and common‑mode suppression at the coax interface.
- Flexible powering: bias‑T over coax or external DC (solar/battery), depending on your site layout.
Technical Overview
Signal Path (schematic‑validated, general terms)
- High‑Z input node + primary surge path (GDT): A low‑capacitance 90 V gas‑discharge tube provides a high‑energy discharge route for ESD/induced surges while keeping the input node lightly loaded at HF.
- Static control (optional bleeder): A jumper‑selectable high‑value bleeder can reference the input slowly to ground when running AC‑coupled, reducing long‑term charge build‑up on stand‑alone high‑impedance elements.
- Optional limiter + optional input shorting relay: A jumper‑selectable limiter (diode clamp with a small series resistor) can be enabled for extra strong‑signal margin. For additional protection/muting, an subminiature relay can hard‑short the input to ground when power over the feedline is asserted.
- Input coupling / DC‑continuity options + optional damping: The input is AC‑coupled by default with a solder‑jumper bypass option for DC continuity in specific use cases (e.g., arrays). An optional small shunt capacitor can be enabled to tame HF peaking or improve stability with “difficult” antenna/feed arrangements.
- Selectable HF roll‑off (low‑pass shaping): A first‑order RC low‑pass (470 Ω series with selectable shunt capacitance) provides two practical bandwidth options: ~18.8 MHz corner (wider) or ~9.4 MHz corner (stronger roll‑off), depending on configuration. This is intentional shaping to reduce out‑of‑band energy and overload risk.
- Low‑noise wideband gain stage: A wideband low‑noise op‑amp stage is used as a non‑inverting RF buffer with selectable gain (≈0 dB or ≈+6 dB). A small HF feedback capacitor is used for stability/compensation.
- Matched output pad + impedance option: A built‑in ≈‑6 dB output pad defines a predictable source impedance for long coax runs: default 75 Ω operation with an optional 50 Ω selection.
- Coax interface hardening + common‑mode suppression: The output is AC‑coupled into a two‑line common‑mode choke (both inner and return paths) to reduce feedline common‑mode currents, followed by coax‑side surge protection and an on‑PCB F‑type connector.
- Flexible powering (bias‑T or external): Power can be injected either via the coax bias‑T node or an external DC input (jumper‑selectable), with filtering, reverse‑polarity protection, and an internal regulated rail for the RF stage.
Performance & Configuration Highlights
| Parameter | Value |
|---|---|
| Intended use | HF receive front‑end at the antenna / start of a long feedline |
| Optimised bands | 160 m / 80 m (optional wider HF coverage via roll‑off configuration) |
| HF roll‑off (‑3 dB corner, 1st‑order RC estimate) | ~18.8 MHz (wider) or ~9.4 MHz (stronger roll‑off), configuration‑selectable |
| Gain modes (pre‑pad) | ≈0 dB or ≈+6 dB (configuration‑selectable) |
| Output matching | ≈‑6 dB matched pad, default 75 Ω, optional 50 Ω |
| Primary surge protection | 90 V GDT at input node + 90 V GDT at coax interface |
| Additional protection options | Optional limiter clamp + optional input shorting relay (mute/protect) |
| Common‑mode suppression | Two‑line common‑mode choke at the coax interface (inner + return) |
| Output connector | F‑type |
| Powering | Bias‑T over coax or external DC (solar/battery), configuration‑selectable |
| 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: It is designed for robust front‑end protection. For best results in high‑RF stations, use proper station sequencing and (when used) assert the input‑mute/short function during TX. Always use external primary lightning/surge protection at the antenna and manage common‑mode currents on the feedline.
- Q: Do I need radials or a ground screen? — A: No. VerticalVortex focuses on a quiet reference and good feedline common‑mode control. 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 often increases noise pickup.
- Q: Will it cover LW/MW DX? — A: The front‑end itself is broadband, but LF/MW results depend strongly on your probe/element and local broadcast environment. If strong broadcast signals cause overload, consider external site‑specific filtering.
- Q: Where to place the choke? — A: At the shack entry point, especially in noisy RFI locations. The interface includes common‑mode suppression, but additional choking at the building entry often improves real‑world noise performance.
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