GPS-Disciplined Shortwave Beacon for High Rate Of Measurement Ionospheric Propagation Analysis

The ionosphere is an undersampled system. Gathering more data points—such as time of flight, Doppler shift, and derivatives (number of hops, type of propagation)—could further our understanding of the ionospheric propagation and enable more in-depth research. This work presents a relatively low-cost, highly repeatable beacon transmitter based on the AD9850 chip, clocked by an external GPSDO. It transmits Costas arrays and phase-modulated timestamps with location data. The AD9850 is loaded in advance by a microcontroller and triggered by the 1PPS pulse of the GPS module. In this design, we aim for a measurable delay of no worse than 100 ns and stability of the delay on the order of tens of nanoseconds. This level of precision translates into time-of-flight measurements with theoretical spatial resolutions on the order of tens of meters, which, given the short length of the signals, allows for rapid, precise measurements at the rate of up to 1 Hz. Such capabilities could allow for the capture of rapid changes and monitoring of the more dynamic processes in the ionosphere.