Stan’s 4 ExpressLRS Receivers Hold 5km Forest Link on 2.4 GHz

Q: What hidden circuit board trick allowed a homemade drone receiver to punch through dense forest interference on just one watt of power?

The key PCB trick was not extra transmit power but a careful antenna-via layout: Stan routed the antenna through a via, which normally risks impedance mismatch, then preserved performance by placing enough nearby ground-plane stitching vias to keep the RF return path intact. That mattered because at 2.4 GHz, the real enemy is often a broken ground return path rather than the via itself. The surrounding ground vias acted like a return-current fence, limiting disruption to the antenna feed and preventing the signal from being badly distorted. In tests, that unconventional layout performed almost the same as a more textbook RF connection. The receiver’s range through dense forest was then made possible mainly by ExpressLRS’s LoRa-derived Chirp Spread Spectrum modulation. ELRS encodes data in chirps, and the receiver dechirps the signal and uses an FFT to recover it, gaining roughly 24 dB in effective sensitivity. That lets it decode signals below the noise floor, which is why links can hold over kilometers even at about one watt. So the “hidden trick” was a subtle board-level RF design choice: using the antenna via without penalty because nearby ground stitching vias preserved the return path. Combined with ELRS’s chirp-based modulation, that helped the homemade receiver maintain control through heavy foliage.

1 articles · Updated · Hackaday · Aug 22

Four custom ExpressLRS receivers built by Stan kept a drone-control connection at more than 5 kilometers even with a forest blocking the path.
2.4 GHz carried most of the test, while two boards also added 900 MHz antennas; the bigger range boost came from ExpressLRS’s Chirp Spread Spectrum modulation rather than simply dropping frequency.
24 dB of equivalent gain from decoding each chirp with an inverse chirp and FFT lets the receivers recover signals below the noise floor, trading data rate for reliability.
An ESP32, an SX1281 radio chip and a few peripherals were enough for the hardware, and even a receiver that routed its antenna through a via showed little performance loss.
ExpressLRS builds on LoRa-style radio techniques that have already posted extreme long-distance records, helping explain how low-power drone links can stretch far beyond line-of-sight conditions.

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Hackaday1d ago

Stan's ExpressLRS Receivers Achieve 5km Range in Forest Test

How can a tiny drone receiver decode control signals from miles away when the transmission is literally weaker than background noise?

What hidden circuit board trick allowed a homemade drone receiver to punch through dense forest interference on just one watt of power?

Could the radar-like chirp technology keeping drones connected over extreme distances completely revolutionize how we design all low-power wireless devices?

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Hackaday1d ago

Stan's ExpressLRS Receivers Achieve 5km Range in Forest Test

Stan’s 4 ExpressLRS Receivers Hold 5km Forest Link on 2.4 GHz

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