SkyTracer — Technical Overview
Updated: 2025-08-12 — Technical overview validated against SkyTracer2 schematic. Capacitive hats confirmed at Ø14 cm (~20–25 pF each). Values with ~ are sweep-derived approximations.
Overview
The SkyTracer is a dual-leg, high-linearity E-field differential dipole designed for low-noise HF reception. It comes in two versions — Standard (0.5 m legs with capacitive hats) and Maxi (1 m legs without hats). Both deliver stable, wideband response from ~50 kHz to 30 MHz and are ideal for NVIS and diversity systems like PolarFlip.
Performance Highlights
- Capacitive hats (Ø14 cm) on Standard extend LF response without increasing element length
- High IP3 (~+41 dBm) differential front-end for strong-signal handling
- Front-end shaping: soft suppression around ~50–55 MHz (keeps 6 m usable but tamed) and a dedicated FM broadcast notch (~88–108 MHz) for ~20–30 dB rejection
- Mount on any mast type (metal or non-metal); typical heights: Standard ~5–6 m, Maxi ~6–8 m
- No radials required; seamless pairing with PolarFlip for 160–40 m NVIS LH/RH diversity
Directional Characteristics
The SkyTracer exhibits a broad cardioid pattern with a deep null on one axis — effective for rejecting local noise sources. Noise can be minimized by orienting the null toward the interference or using two units in complementary orientations.
Measured Band Performance — Standard vs Maxi
| Band | Freq (MHz) | Std Gain (dBi) | Maxi Gain (dBi) |
|---|---|---|---|
| 160m | 1.8 | ~28 | ~35 |
| 80m | 3.5 | ~26 | ~31 |
| 40m | 7.0 | ~24 | ~27 |
| 30m | 10.1 | ~23 | ~24 |
| 20m | 14.0 | ~23 | ~23 |
| 17m | 18.1 | ~23 | ~23 |
| 15m | 21.0 | ~23 | ~23 |
| 12m | 24.9 | ~23 | ~23 |
| 10m | 28.5 | ~23 | ~23 |
Preselection & Usable Bandwidth
- System bandwidth: response extends to ~60 MHz+
- 6 m region (~50–54 MHz): intentionally softened to reduce overload; casual monitoring still possible
- FM broadcast (~88–108 MHz): notched by ~20–30 dB to preserve linearity in urban sites
- Takeaway: the chain is broadband, but parts of VHF are deliberately de-emphasized for cleaner HF performance
Technical Note
On LF/MF, physical element length directly impacts E-field capture. The Maxi’s 1 m legs yield ~7 dB more gain on 160 m and ~5 dB more on 80 m compared to the Standard. Above ~10 MHz, both behave as electrically short probes, so gain is set by the flat amplifier response — making HF performance essentially identical.
The Standard’s capacitive hats increase capacitance at the element tips, effectively lengthening them electrically without extra height, retaining strong LF sensitivity in compact form.
Core Specifications
| Parameter | Standard | Maxi |
|---|---|---|
| Leg Length | 0.5 m | 1.0 m |
| Capacitive Hat | Ø14 cm (~20–25 pF) | N/A |
| Frequency Range | ~50 kHz – 30 MHz (usable response to ~60 MHz; 6 m softened, FM band notched) | |
| Best Performance | 80–10 m | 160–10 m |
| Placement | Typical heights: Standard ~5–6 m; Maxi ~6–8 m | |
| Amplifier | High-IP3 differential, push-pull | |
| CMRR | > 55 dB typical | |
| TX Tolerance | Up to 2 kW @ ~12 m distance | |
| Supply Voltage | 12–15 VDC via Bias-T | |
| Current Draw | ~150 mA | |
For leg junctions, bolts, and feed connections, apply AL-1100 aluminum paste during installation. It prevents galvanic corrosion, maintains stable impedance, and ensures long-term reliability in outdoor environments.
How often? One careful application at install is typically sufficient. In coastal or industrial areas, reapply every 2–3 years during inspection, or whenever hardware is loosened and retightened.
PolarFlip Companion
Two SkyTracer units — Standard, Maxi, or a mix — can be phased for PolarFlip diversity reception. Matching versions ensure symmetrical patterns, but mixing is possible if low-band gain asymmetry is acceptable.
Mini-FAQ
- Do I need radials? — No, fully active E-field dipole.
- Which version for top band? — Maxi for +7 dB gain on 160 m.
- Why use capacitive hats? — Electrically lengthens short legs without added height.
- Can I mount on a metal mast? — Yes, no degradation.
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