TerraBooster Medi — Technical Overview
Updated: 2025-08-11 — Technical overview validated against schematic and sweep measurements. Values with ~ are sweep-derived approximations.
Overview
The TerraBooster Medi is a 32-meter circumference (H-field) shielded ground loop receive antenna designed for 160–10 meter operation, with usable response into 6 meters. Its high-linearity differential amplifier and large loop aperture deliver strong low-band performance while maintaining excellent common-mode rejection in noisy environments.
Performance Highlights
- ~1.2 mA/m² loop sensitivity on 160m for NVIS and DX
- High IP3 (~+42 dBm) push-pull front-end for strong-signal environments
- Low noise floor thanks to shielded H-field coupling (<15 cm above ground)
- No radials required — operates effectively over soil, grass, or concrete
- Stable gain across 160–10m, with mild roll-off above 30 MHz
- Integrated low-pass network (~32 MHz) to suppress strong FM/VHF interference
Directional Characteristics
Unlike most compact ground-level receive antennas, the TerraBooster Medi exhibits mild directionality. When deployed in open space, it produces a broad cardioid pattern with maximum sensitivity perpendicular to the loop, and slightly reduced sensitivity in line with the coaxial feed ends.
This directionality is useful for rejecting localized noise or enhancing signals from a preferred direction. A 90° reorientation can noticeably change received noise levels.
- Single orientation: Best for targeting a primary direction.
- Dual 90° rotated: Covers complementary directions, switchable.
- Opposing pair: “X” layout for dual-opposite coverage — ideal for PolarFlip LH/RH NVIS reception (160–40m).
Measured Band Performance (Medi – 32m circumference)
| Band | Frequency (MHz) | Elevation Angle (°) | Total Gain (dBi) |
|---|---|---|---|
| 160m | 1.8 | 75 | ~-26 |
| 80m | 3.5 | 65 | ~-18 |
| 40m | 7.0 | 55 | ~-12 |
| 30m | 10.1 | 45 | ~-6 |
| 20m | 14.0 | 45 | ~-6 |
| 17m | 18.1 | 35 | ~-2 |
| 15m | 21.0 | 25 | ~+2 |
| 12m | 24.9 | 25 | ~+2 |
| 10m | 28.5 | 25 | ~+2 |
Core Specifications
| Parameter | Value |
|---|---|
| Loop Type | Shielded H-field coaxial loop |
| Loop Circumference | 32 m (Medi) |
| Frequency Range | ~50 kHz – 60 MHz |
| Best Performance | 160–10 m |
| Placement | On ground or <15 cm above ground |
| Amplifier | Differential, high-IP3 push-pull |
| Output Impedance | 75 Ω (SMA adapter included) |
| CMRR | >60 dB typical |
| TX Tolerance | Up to 2 kW @ 12 m |
| Supply Voltage | 13.8 V via Bias-T |
| Current Draw | ~180 mA |
For all bolts, screws, and coax connectors, apply AL-1100 aluminum paste during setup. It prevents galvanic corrosion at the loop junctions and ensures low-loss RF contact in long-term outdoor use.
How often? One careful application at installation is normally sufficient. In harsh coastal or industrial areas, reapply every 2–3 years during inspection, or sooner if connections are opened.
PolarFlip Companion
The TerraBooster Medi is a perfect low-band (160–40m) companion for the PolarFlip LH/RH phasing system. Two Medi units in a cardinal or opposing arrangement enable polarization diversity reception, significantly reducing QSB and improving NVIS stability — especially effective in noisy low-band conditions.
Mini-FAQ
- Do I need radials? — No, the TerraBooster Medi is a closed-loop H-field design and requires no radials.
- How high should it be? — Best performance is at ground level or up to 15 cm above ground.
- Can it be rotated? — Yes, rotating changes noise rejection and signal emphasis.
- Can I combine two units? — Yes, for direction diversity or PolarFlip NVIS configurations.
Interested in more technical content like this? Subscribe to our updates for deep-dive RF articles and lab notes.
Questions or experiences to share? Feel free to contact RF.Guru.