Which device is used as the internal timekeeping source in most GPS receivers?

• A. Quartz crystal oscillator
• B. Cesium clock
• C. Rubidium clock
• D. Solar-powered oscillator

Answer: (A)

A quartz crystal oscillator serves as the time base for most GPS receivers. The receiver needs a stable local clock to generate its internal reference frequencies and to track the code and carrier signals from satellites. Quartz crystals provide a compact, inexpensive, low-power, and sufficiently stable timing source for everyday navigation tasks. The GPS system itself gives precise time via its satellite clocks, but the receiver does not carry an atomic clock; it measures its own clock bias relative to GPS time as part of the positioning solution. In higher-end gear, more stable devices like rubidium or cesium clocks can be used for better hold-over, but they’re not the norm in most receivers. A solar-powered oscillator isn’t a standard timekeeping device in GPS receivers.