On Thursday, May 9, 2019 at 9:14:45 AM UTC-4, son_of_flubber wrote:
https://www.faa.gov/other_visit/avia.../InFO19006.pdf

That PDF is short on details, but seems to imply that the transmissions from the SPOT device cause a nearby GPS receiver to have problems. Since the SPOT only transmits once in several minutes, do the observed GPS position losses only occur at those times and briefly? I wonder what the power and frequency of SPOT's transmissions are. We use many other devices in our cockpits that transmit periodically in VHF or UHF, e.g., transponders (high power!), FLARM (low power), cellphones (medium power), Bluetooth (low power), VHF radio (medium power), goTenna (medium power), switching power supplies (low power in any given frequency). Do any of these interfere with GPS reception? Actually I am amazed how well GPS receivers do in listening to very faint signals from the satellites, in the face of all the electric noise, and often poor "view of the sky" (e.g. the pilot's body nearby).