KerberosSDR — 4-Channel Coherent RTL-SDR for Direction Finding

The KerberosSDR is a four-channel coherent software defined radio system built for direction finding (DF) and passive radar applications that are impossible with a single-receiver SDR. Four RTL-SDR receivers share a single reference clock and noise source calibration circuit, enabling phase-coherent sampling across all four channels simultaneously.

When paired with a four-element antenna array and the open-source KrakenSDR or Kraken Android app, the system performs real-time direction-of-arrival estimation using MUSIC, Bartlett, and Capon algorithms — visualising the angular bearing of any RF source in view. Applications include amateur radio foxhunting (ARDF), interference hunting, wildlife radio collar tracking, and passive radar demonstrations using DVB-T and FM broadcast illuminators.

• 4× RTL2832U receivers with shared 28.8MHz reference clock
• Frequency range: 24–1766MHz per channel
• Phase coherent sampling: all 4 channels synchronized
• Noise source for automatic phase calibration
• SMA connectors × 4
• USB hub board (powered from single USB-C input)
• Compatible with KrakenSDR app, GNU Radio, Python