PiRadar node array under ionosphere
PiRadar nodes in arbitrarily shaped array for ionospheric imaging via pseudonoise HF radar waveforms.

We propose a dense network of dual-mission HF radars costing $300 – PiRadar costs 95% less than contemporary radar nodes using the latest COTS SDR technology, simultaneously:

  • improving ionospheric models via measurements as an alternative or complement to GNSS TEC measurements
  • 4-D imaging of the Earth’s atmosphere/ionosphere
  • data relay from isolated sites (e.g. flood alarm, tracking animals)
  • Solar storm impact detection and quantification
  • Ground-based GPS time-transfer and location service alternative
PiRadar block diagram
PiRadar high-resolution polarization-sensitive HF radar node block diagram.

A simplified system using one antenna for transmit & receive is shown below. Also shown in this figure is a means to inject 1PPS directly into transmit and receive RF streams, in case there is an issue with hardware triggering of DAC or ADC–applicable to general receivers such as RTL-SDR. In this diagram, a maximum 20 dBm transmit power is assumed.

PiRadar TX/RX Pulse, single antenna block diagram
PiRadar TX/RX 1PPS pulse injector, single antenna block diagram.

PiRadar Specifications

PiRadar performance metric value
range resolution 1..25 km
data rate 1..20 kbps
transmit power 1..100 mW
transmit bandwidth 6 kHz..1 MHz
node-to-node communication range (skywave) 50..500 km

Prior Work in HF sounding networks

Tiddbit CW HF oblique sounder works in the 2..10 MHz range, transmit power ~ 100 watts.