According to Professor GOOGLE: 150 feet
GPS Antenna Cable Configurations/Options. Antenna cabling solutions typically vary depending on how far the antenna is installed from the GPS receiver . 150 feet (45 m) is the unaided cable length limit for many GPS timing receivers . Adding a GPS inline amplifier extends the cable length an additional 150 feet (45 m).
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GPS Antennas & Cable — Masterclock, Inc.
](https://www.masterclock.com/support/gps-antenna-and-cable-information)