SDR Field Companion
A phone app that pairs with a portable SDR dongle and Rotman-lens-fed antenna array to show live beam direction, signal-strength heatmap, and detected aircraft or satellite passes — turning a backyard RF rig into a usable passive radar.
Amateur radio operators and STEM students exploring radar and satellite reception
- Live heatmap of received signal strength as you sweep beam ports on your array
- Pre-loaded satellite and ADS-B databases with pass predictions over your location
- Recording mode that captures IQ snapshots when a target exceeds a threshold
- Step-by-step build guides for constructing a Rotman-fed array from off-the-shelf parts
Cheap SDR hardware ($25 dongles) plus a working Rotman design makes backyard passive radar realistic; an app is the missing software layer that turns hardware into a usable hobby.
Passive-radar/SDR hobby has a documented community (IEEE Spectrum how-to, Hackaday tag with multiple projects, WHY2025 conference talk, RTL-SDR blog posts), but it remains a small niche within the ham/STEM crowd; the HN Rotman-Lens hit was modest at 66 points.Build a Passive Radar With Software-Defined Radio ↗WHY2025 Conference: Passive and Active RADAR using Software Defined Radio ↗
No phone app combines Rotman-lens beam-direction visualization + passive-radar signal processing; existing mobile tools cover only single slices (ADS-B only, generic SDR only) and PC tools like SDRDue handle passive radar but not on a phone with a lens-fed array.SDRDue Updated: Passive Radar Software for RTL-SDRs ↗
Comparable paid mobile SDR apps price around £5.99 one-time (SDR Touch); ham/hobby buyers do pay modest sums for niche tools, but addressable market is tiny (likely thousands, not millions) and free open-source PC alternatives (SDRDue, PassiveRadarSim) cap willingness-to-pay.GitHub - bradleeharr/PassiveRadarSim ↗
SDR hobby has been steady for ~15 years with recurring educational and maker interest (conferences, IEEE/Hackaday coverage); Rotman-lens DIY content continues to appear, but the niche isn't expanding into mainstream consumer territory, suggesting durable but flat demand.Rotman Lens - Radartutorial ↗passive radar - Hackaday ↗
Building blocks exist (SDR Touch proves phone+RTL-SDR via USB-OTG, SDRDue proves the passive-radar DSP, Rotman-lens designs are published), but integrating them into a calibrated beam-direction + heatmap UI with real-time ambiguity-surface rendering on a phone is a substantial engineering effort; the IEEE piece notes passive-radar signal processing is computationally heavy.Build a Passive Radar With Software-Defined Radio ↗