GRAPE 2 fldigi - Overview, Specifications, Sourcing

 

G2 Complete Asbly 2024-02-15 cropped.png 2024-04-08 AF8A Grape 1 Total Eclipse Grape1 fldigi plot.jpg

Overview

The three-channel GRAPE 2 Doppler Monitor (fldigi version) is a key component of the HamSCI Personal Space Weather Station (PSWS).  It could be considered the 'next generation' of GRAPE receiver, released just prior to the April 8, 2024 North American solar Eclipse.   It is used for receiving, analyzing and recording of signals from frequency standard stations such as WWV/H and CHU. The PSWS project involves monitoring changes in the Earth's ionosphere through measurements of Doppler frequency shifts on a 24/7 basis. 

The Grape 2 could be considered the 'big brother' of the GRAPE PSWS family. It is capable of receiving three frequencies simultaneously, utilizing a GPS disciplined oscillator for making precise frequency measurements.  A complete GRAPE 2 PSWS system (as pictured above) consists of the following: Grape 2 Receiver and Logic PC boards, Teensy microcontroller, Raspberry Pi 4, external hard drive, power supply and two antennas, one for the GPS and one for the time standard frequencies. Ideally, every Grape 2 should have access to a reasonably fast (>100Mb/S) Internet connection for data uploads. There is a provision to buffer and transmit buffered data at a later time if the connection is lost. Data collected by the GRAPE 2 is intended to be uploaded on a daily basis to a HamSCI server.   The data collected by a Grape 2 can be used to generate plots of Doppler shift vs. UTC hour.  A sample plot from  April 8, 2024 (the date of the recent North American total solar eclipse) appears above.  (The solar eclipse's effect on the ionosphere is clearly visible between about 1800 and 2100 UTC.)

Specifications

Purpose Three frequency, low-IF receiver, used for measuring Doppler shift while receiving frequency standard stations such as WWV/H or CHU.  Data is useful for studying bottom side motion of the ionosphere.
Frequency Selections 2.5, 5.0, 10.0 or 15.0 MHz (reduced though very acceptable performance on 3.33, 7.58 or 14.36 MHz)
Frequency Stability As stable as the Leo Bodnar GPS disciplined oscillator, approaching 1x10-12 
Sensitivity Under review
Dynamic Range Under review
Received Bandwidth Under review
Current Hardware Version 1.0.  No further revisions or production is planned.
Required Computer Raspberry Pi 4B, 8 GB memory
Operating System Raspbian OS
Required software fldigi, a ham radio modem application, numerous GRAPE-specific shell scripts
Data Repository The GRAPE 2 fldigi data is freely accessible, available in the HamSCI Community on Zenodo.org 

Sourcing

Approximately 30 GRAPE 2s were manufactured and tested late in Q1, 2024. They were deployed in accordance with terms of the grants which funded the project: A map of the stations appears on this page. They were on line and uploading data during the April 8, 2024 North American total solar eclipse. It is HamSCI's expectation that all will be kept running, on a 24/7/365 basis, for years to come, studying the behavior of the ionosphere during Solar Cycle 25. Further, some GRAPE 2 installations included remote magnetometer boards, used to measure minute changes in the Earth's magnetic field. That data was sent to the same HamSCI server.

Occasionally, units are returned to HamSCI for redeployment.  If you are interested in hosting a grand-funded GRAPE 2, please send your contact info, including location (grid square and city/state/province) to hamsci@hamsci.org.  Note that grantees are expected to have basic Linux experience, an HF (shortwave) antenna, and common computing peripherals (USB keyboard/mouse, monitor) and an Internet connection for daily data uploads. Of course, we can't guarantee availability but we are very interested in having as many systems running as possible.

Further Information


Images of the Grape 2 under development at the bench of John Gibbons, N8OBJ:

G2DevSetup.jpeg
G2Running.jpeg

 

Grape 2 Hosts

30 Grape Version 2s were deployed prior to the April 8, 2024 total solar eclipse over North America.  The host stations are shown on this map.

 

Credits

The Grape Version 2 was designed by John Gibbons, N8OBJ, Lab Director of the Sears Undergraduate Electrical Design Lab, Case Western Reserve University, Department of Electrical Engineering. Software applications were written by Bill Blackwell, AB1XB and Cuong Nguyen, KC3UAX. The remote magnetometer board was designed, built and provided to host stations by David Witten, KD0EAG. Dr. Nathaniel Frissell, W2NAF, was the Principal Investigator on National Science Foundation grant 2230345 ('Collaborative Research: CEDAR: Measuring Daily Ionospheric Variability and the 2023 & 2024 Solar Eclipse Ionospheric Impacts Using HamSCI HF Doppler Shift Receivers'). Their efforts were supported by additional NSF grants (2002278, 1922972, 1932997, 2230346) and these institutions:

hamsci_collaboration.png