The GRAPE 2 Doppler Monitor is a three-channel HF receiver developed as part of the HamSCI Personal Space Weather Station (PSWS) project. It was released shortly before the April 8, 2024 North American solar eclipse as a next-generation system designed to monitor Doppler frequency shifts in HF time-standard signals such as WWV, WWVH, and CHU. GRAPE 2 is capable of simultaneously receiving three frequencies, with primary frequency selections at 2.5, 5.0, 10.0, and 15.0 MHz, and reduced though very acceptable performance on 3.33, 7.58, or 14.36 MHz. It utilizes a GPS-disciplined oscillator (GPSDO) for precise frequency measurements. The GRAPE 2 system consists of receiver and logic PCBs, a Teensy microcontroller, a Raspberry Pi 4B running Raspbian OS, an external hard drive, and two antennas—one for GPS reception and one for HF time-standard signals. It is used for continuous monitoring of the ionosphere through measurements of Doppler frequency shifts as part of the PSWS network.

The AB4EJ Grape 2 station is located at 33.417ºN, 87.583ºW. Instrument type is Grape 2. There is one antenna at this station, which is 80 m dipole antenna. It records WWV 5 MHz, 10 MHz, and 15 MHz Doppler Shift.