Grape 1 Personal Space Weather Station

The Grape 1 software defined receiver (SDR) is a key component of the HamSCI Personal Space Weather Station (PSWS).  The Grape 1 was designed with specific purposes in mind:  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.

Ham radio operators and shortwave enthusiasts are encouraged to host Grape 1 SDRs at their stations from now until well after the total North American solar eclipse on April 8, 2024.  Hosting involves providing reliable power, space for an antenna and an Internet connection.  Other factors come into play, such as the need for visibility to the constellation of GPS satellites.

A complete description of the PSWS, including an explanation of the science questions driving the need for the Grape 1 (and its big brother, the Grape 2) is available here.

Anatomy of the Grape 1 PSWS

The Grape 1 is designed for the DIY enthusiast.  The single-frequency receiver portion is built by the user on a PC board using surface mount components.  It is designed for use on 2.5, 5.0, 10.0 or 15.0 MHz.  (Operation on CHU frequencies of 3.33, 7.58 or 14.36 MHz are possible with reduced performance.) It is one of a half-dozen system components:  A GPS disciplined oscillator, a Raspberry Pi with a USB sound card, power supply and antenna.  All components are readily available and thoroughly documented below.  This video (courtesy of the American Radio Relay League) provides an excellent overview of the current version, known as the Grape 1.12.  (Archival information for the previous version, Grape 1.11 {no longer available} is here).

Please note that the Grape 1 receivers are not general purpose software defined receivers (SDRs). They are designed to receive signals only on frequencies pertinent to the research goals.

Building the Grape 1 PSWS

Building the a Grape 1 PSWS is not as easy as the old HealthKits used to be.  For starters, there is no kit of components.  The instructions are fairly complete, but they are not 'cookbook style'.  It will take some digging and planning on the part of the builder.  Fortunately, help is not far away:  Join the hamsci-grape Google group and you'll find many others who've 'been there, done that' and who can help you if you get stuck.  You can also navigate over to the Google group and 'search' on any topic or question you might have.  It's possible that the answer you are looking for will appear in the search results!

One Ham's Perspective on Building a Grape PSWS: K4BSE_Grape 1.12 Document v1-2.pdf

Grape V1.12 Block Diagram: PSWS_GrapeLowCostBlockDiagram.pdf

Grape V1.12 schematic:  WWV_Radio_V1_12_sch.pdf

Grape V1.12 Bare PC Board Ordering Link from

Grape V1.12 PC Board Bill of Material (BOM):  WWV_Radio_V1_12_bom.txt

Grape V1.12 PC Board BOM Components Order Link from

Grape V1.12 Builder Instructions, Testing, System Assembly and Operation;  NOTE:  This document was written for a previous hardware version, so the PC board component lists and schematics are not accurate for the V1.12 PCB.  However, the majority of the instructions in Sections 5, 6 and 7 do apply to version 1.12:  PIIS2468067222000347.pdf

Grape PSWS System Components, including the Leo Bodnar GPS: GrapeGen1_SuppliesList.pdf

How to Request a Node Number: Request a PSWS_Node_Number.txt

Obtaining the Grape PSWS Raspberry Pi Image File:  Navigate to and search for Grape Version 1.  When found, open the folder Grape Gen 1 OS Update V1.2.  Download the file  Follow the 'Builder Instructions' referenced above to burn the image onto an SD Card.

Many more design details are available, follow this link and search for Grape Version 1:


The Grape Version 1 was designed by John Gibbons, N8OBJ, Lab Director of the Sears Undergraduate Electrical Design Lab, Case Western Reserve University, Department of Electrical Engineering.  Many thanks to these institutions for assisting John's efforts.

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