GRAPE-1

The GRAPE-1 system is designed to monitor how the Earth’s ionosphere changes over time. It does this by continuously listening to a known, fixed-frequency, and stable HF time signal (Source). These signals include WWV & WWVH (USA), CHU (Canada), RWM (Russia), and BPM (China). The Grape-1 platform mixes signals received with a GPSDO derived reference frequency set slightly away from that of a known HF time-signal station frequency. The output of this mixing process produces an audible tone. Variations in the frequency of that tone are directly related to changes in the Source frequency. Tone frequency variation data is collected over time and stored in a digital format for subsequent analysis. These data thus provide the means by which ionospheric changes may be monitored (Collins et al. 2021, Collins et al., 2022).

Two versions of GRAPE-1 are available, they differ in the method of signal processing and reporting of data.

Full details are via these links:

• GRAPE-1 fldigi.

• GRAPE-1 digitalRF

The GRAPE Version 1 hardware was designed by John Gibbons, N8OBJ, Lab Director of the Sears Undergraduate Electrical Design Lab, Case Western Reserve University.

References Collins, K., Montare, A., Frissell, N. and Kazdan, D., 2021. Citizen scientists conduct distributed doppler measurement for ionospheric remote sensing. IEEE Geoscience and Remote Sensing Letters, 19, pp.1-5. Online

Collins, K., Gibbons, J., Frissell, N., Montare, A., Kazdan, D., Kalmbach, D., Swartz, D., Benedict, R., Romanek, V., Boedicker, R. and Liles, W., 2022. Crowdsourced Doppler measurements of time standard stations demonstrating ionospheric variability. Earth System Science Data Discussions, 2022, pp.1-21. Online