SPINE — covert short-range radio

Overview

Field operators need devices that talk to each other over short range without an adversary detecting the transmission, and without the wire clutter of tethered gear. As Networks Lead I designed the custom communication protocol — tuned for low power, short range, and a small electromagnetic footprint — across a mix of Raspberry Pi, Teensy, RP2040, and NRF24 radio hardware. The work spans a first-generation stack, a reworked second generation, the radio-transmitter layer, and HINT, a field configuration loader. Demonstrated working covert comms across two hardware generations.

Design decisions 05

• One protocol runs across heterogeneous boards — Raspberry Pi, Teensy, Pico — rather than locking to a single platform, because operators in the field carry mixed hardware.
• The short-range NRF24 band was targeted deliberately, trading transmission range for a smaller electromagnetic signature; the goal was non-detection, so stealth was chosen over reach.
• The radio link was benchmarked empirically on a dedicated bandwidth bench, and the protocol’s framing was sized to the measured throughput ceiling instead of datasheet figures, which overstate real NRF24 performance.
• HINT loads new configuration the moment a USB drive is inserted, zero interaction — because an operator cannot be typing configs under field stress.
• Signal isolation for demos was proven with a makeshift Faraday cage — a 3D-printed frame wrapped in aluminum foil — a cheap way to show the transmission stayed contained without lab RF equipment.

custom RF protocol · NRF24L01 · Raspberry Pi · Teensy · RP2040 · MicroPython

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