Not sure how the GPS NUDET system works but I suspect the downlink is something other than the navigation signal. Spoofing the navigation signal would not affe

Not sure how the GPS NUDET system works but I suspect the downlink is something other than the navigation signal. Spoofing the navigation signal would not affect the GPS telemetry signal to dedicated NUDET ground stations. BTW, the device you linked is used exactly for that purpose, to shut down electronics to prevent damage from EMP and other effects. To your point, there are other means to detect nuclear explosions, used mostly to verify compliance with treaties, such this seismic one: https://www.osti.gov/servlets/purl/1582524 https://www.osti.gov/servlets/purl/1582524