RF Guru
13.8v LoRa APRS Automotive Tracker 433 Mhz 400 mW CE
13.8v LoRa APRS Automotive Tracker 433 Mhz 400 mW CE
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Included
- Custom RF.Guru enclosure
- Alpha19 GPS Square Antenna
- RF Solutions 433 MHz Patch Antenna (SMA)
- Pre-programmed (request via email after ordering)
- Assembled and rigorously tested
Product Overview
The RF.Guru LoRa APRS Tracker is a compact, vehicle-ready tracker for ham radio APRS. It combines a Raspberry Pi RP2040 MCU with a 433 MHz LoRa RF stage and a high-sensitivity GNSS receiver to deliver reliable long-range beaconing. Built-in voltage monitoring and optional temperature/humidity sensing provide additional system health and environmental data.
Quick Highlights
- Clean 3-rail power design with low ripple & protection
- Active GNSS bias and filtering for robust GPS lock
- Filtered LoRa PA chain for pure RF output & compliance
Key Features
- 433 MHz LoRa APRS with ~400–500 mW RF output for extended coverage
- GNSS with active antenna biasing and filtering for solid satellite lock
- Vehicle voltage monitoring with protected ADC input
- USB-C for firmware updates and configuration
- 13.8 V PowerPole DC input; ultra-low idle draw (<0.5 W)
- LED indicators for Power, GPS lock, and APRS TX
Datasheet
- PCB finish: ENIG (Electroless Nickel Immersion Gold)
- MCU: RP2040 with external QSPI flash
- RF: 433 MHz LoRa transmitter chain with filtering and gain stage
- RF output: 26 dBm (≈400 mW)
- Interfaces: USB-C, PowerPole 13.8 V, SMA GNSS & 433 MHz RF
- Indicators: Power / GPS lock / APRS TX
- Power: ~3.7 W TX / <0.5 W idle
Software
Open-source firmware: https://github.com/Guru-RF/LoRa433APRSTracker
Schematic Highlights
- Power architecture: 13.8 V input regulated down to 5 V, then low-noise 3.3 V rails. Includes soft-start, reverse/over-current protection, and LC filtering.
- USB interface: D+/D– lines filtered with ferrite beads, shunt caps, and ESD protection array. Proper CC pull-downs ensure cable compatibility.
- GNSS RF path: SMA input with bias-T powering active antennas. Isolated supply filtering ensures stable GPS performance.
- LoRa RF chain: SPI-driven stage into an RF gain block and low-pass filter, ensuring clean RF delivery to the antenna.
- Voltage sensing: Scaled, filtered, and clamped input protects the RP2040 ADC while maintaining accuracy.
- GPIO & expansion: Exposed I²C/IO header. LEDs (Power / GPS / TX) are RP2040-driven with current-limiting resistors.
CE RED Spurious Emission Test
Measurements with calibrated VNA and 36 dB attenuator. Worst-case harmonic: 3rd harmonic at −73.6 dBc.
Surpasses ETSI EN 300 220 (−43 dBc for ≤30 dBm transmitters) by ~30 dB margin, ensuring excellent spectral purity and compliance.
Shipped with an advanced Siretta GPS antenna and an RF Solutions 433 MHz patch antenna.
