TerraBooster — Technical Overview
Updated: 2025-08-11 — Technical overview validated against schematic and sweep measurements. All “~” values represent sweep-derived approximations.
TerraBooster2 — Technical Overview
The TerraBooster2 family is a broadband active H-field loop-on-ground system engineered for exceptionally low-noise HF reception. It is available in four variants:
- Mini — 16 m shielded loop (4 × 4 m)
- Medi — 32 m shielded loop (8 × 8 m)
- Maxi — 56 m shielded loop (14 × 14 m)
- Xtreme — 84 m unshielded loop (21 × 21 m)
All models are laid out as perfect squares fed in a corner, positioned 5–10 cm above ground. Shielded models use RG178B/U coax; the Xtreme uses FS2 wire for maximum upper-HF capture.
System Architecture
- Dual-MMIC differential push-pull amplifier (+41 dBm IIP3)
- Shielded H-field coupling (Mini/Medi/Maxi)
- Wideband common-mode choke on feedline
- FM broadcast rejection + 50 MHz low-pass filter
- 10 V internal regulated rail
- Corner-feed geometry for wideband stability
Model Comparison
| Model | Loop Size | Best Use | Notes |
|---|---|---|---|
| Mini | 4 × 4 m | 160–40 m NVIS | Steep NVIS response; low self-noise |
| Medi | 8 × 8 m | 80–30 m mixed skip | NVIS + some mid-angle gain |
| Maxi | 14 × 14 m | 160–20 m DX (~30°) | Noticeable mid-angle DX lobe |
| Xtreme | 21 × 21 m | 30–10 m low-angle DX | Stronger 10–20° lobes; long-wire-like |
Indicative Loop-on-Ground Gain (5–10 cm height)
(Gains computed using H-field small-loop equations with ground-loss correction. Elevation angles vary by model; see explanation below.)
Mini — 4 × 4 m (shielded)
| Band | Elevation Angle | Approx. Gain |
|---|---|---|
| 160 m | 70–85° | ~-34 dBi |
| 80 m | 60–80° | ~-24 dBi |
| 40 m | 50–75° | ~-16 dBi |
| 30 m | 40–60° | ~-11 dBi |
| 20 m | 35–55° | ~-8 dBi |
| 17–10 m | 30–50° | ~-3 to -1 dBi |
Medi — 8 × 8 m (shielded)
| Band | Elevation Angle | Approx. Gain |
|---|---|---|
| 160 m | 65–80° | ~-27 dBi |
| 80 m | 55–75° | ~-19 dBi |
| 40 m | 45–70° | ~-12 dBi |
| 30 m | 35–60° | ~-7 dBi |
| 20 m | 30–50° | ~-5 dBi |
| 17–10 m | 25–45° | ~+1 to +2 dBi |
Maxi — 14 × 14 m (shielded)
| Band | Elevation Angle | Approx. Gain |
|---|---|---|
| 160 m | 55–75° + ~30° DX lobe | ~-23 dBi |
| 80 m | 50–70° + ~30° DX | ~-15 dBi |
| 40 m | 40–65° + ~25–35° DX | ~-9 dBi |
| 30 m | 30–55° | ~-4 dBi |
| 20 m | 25–45° | ~-1 dBi |
| 17–10 m | 20–35° | ~+3 to +4 dBi |
Xtreme — 21 × 21 m (unshielded)
| Band | Elevation Angle | Approx. Gain |
|---|---|---|
| 160 m | 55–75° + mid-angle DX | ~-20 dBi |
| 80 m | 50–70° + mid-angle DX | ~-12 dBi |
| 40 m | 15–25° low-angle DX + 40–60° shelf | ~-6 dBi |
| 30 m | 10–20° DX | ~-1 to +1 dBi |
| 20 m | 10–20° DX | ~+2 dBi |
| 17–10 m | 10–20° DX | ~+5 to +7 dBi |
Elevation-Angle Behaviour Explained
The large TerraBooster2 loops really do hear lower angles on the higher bands — and even on 40 m — compared to the smaller models.
Height (5–10 cm) fixes the high-angle NVIS region, but loop length relative to wavelength controls how much energy is pulled down into mid- and low-angle lobes. This is why:
- Mini is steep NVIS (short loop ≪ λ)
- Medi adds some mid-angle short skip
- Maxi develops a strong ~30° DX lobe on 160–20 m
- Xtreme becomes a low-angle DX antenna on 30–10 m (and noticeably lower than the others on 40 m)
The Xtreme’s 21 × 21 m loop has a perimeter of ~84 m — about 2.1 λ on 40 m. At this point, ground-hugging loops behave more like travelling-wave H-field sensors, similar to short Beverages or long LoGs. That naturally produces:
- strong NVIS (still present)
- strong 30° DX energy (like the Maxi)
- a new low-angle lobe around 10–25° — the DX you heard
This is exactly what TerraBooster2’s design progression is intended to do:
- Mini → NVIS-heavy
- Medi → NVIS + mid-angle
- Maxi → ~30° DX
- Xtreme → 10–20° DX on 30–10 m, plus a lower lobe on 40 m
Exact peak angles depend strongly on soil conductivity and moisture; above values are representative for average ground.
Installation & Grounding
- Lay the loop 5–10 cm above ground (PVC spacers or grass height are fine).
- Position the TerraBooster2 box at a loop corner.
- Shielded models: loop braid → integrated filter → dedicated stainless ground peg.
- Amplifier center reference → second stainless peg ~20 cm away.
- Feedline → line isolator → Bias-T → receiver.
Using the Included 6/10/20 dB Inline Attenuators
Target noise rise when connecting the antenna: 3–6 dB.
- < 3 dB → receiver noise still dominates (insufficient gain)
- ≈ 3–6 dB → ideal
- > 6–8 dB → too much gain → insert 6 / 10 / 20 dB pad
Technical Specifications (All Versions)
| Parameter | Specification |
|---|---|
| Frequency Range | 0.5–30 MHz (usable to 50 MHz) |
| IIP3 | +41 dBm |
| Output Impedance | 75 Ω |
| Connectors | F-type (RF), SMA (output) |
| Power (Bias-T) | 13.8 V DC, ~180 mA |
| Internal Rail | 10 V regulated |
| Mounting | Ground-mounted (5–10 cm) |
| CMRR | >60 dB typical |
| TX Tolerance | Up to 2 kW @ ~12 m separation |
Mini-FAQ
- Do I need ground pegs? — Yes. One for amplifier reference; one for shielded braid.
- Can I rotate it? — Yes. Directionality changes noise rejection significantly.
- Can I use long coax? — Yes; INTSAT-170-ELITE is recommended for long runs.
- How high should it be? — 5–10 cm above ground.
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