Passive radar
Passive radar compares a broadcast transmitter's direct signal with its echoes off aircraft and
other objects. It measures how much further each echo travelled and its Doppler shift. Two lanes
on a shared clock are enough; a time_sync array works without phase calibration.
Set up
- Add a Device or Array with at least two time-synced lanes.
- Add Passive radar.
- Wire the antenna pointing at the transmitter to
ref. - Wire the antenna pointing at the area you watch to
surv. - Wire GPS position for the map.
| Setting | Does |
|---|---|
| Integration | Longer finds weaker echoes, but blurs moving ones |
| Range bins | How far out the display reaches |
| Doppler span | How large a frequency shift to search |
Processing runs in five steps: cancel the direct signal and ground clutter, correlate reference with surveillance, detect cells above their background, merge neighbours, and track echoes over time.
Read the display
The display plots range against Doppler and marks detections. An echo seen repeatedly gets a track number. A single flash may be noise.
On the map
Turn on Transmitter and enter its position and frequency. With your own position known, the map draws an ellipse of possible locations for each echo.
The range is bistatic: the extra distance the echo travelled compared with the direct path. One echo gives an ellipse, not a point or a bearing.
On a phone, use the Radar watch mission in field mode.