Frequency Calibration via GPS

Inexpensive Frequency Standard with output synchronized to GPS satellites,

Features

• U-Blox NEO-7M GPS Module
• Remote Amplified GPS Antenna
  • SMA Male connector
• FTDI-49MM
  • Used to program the GPS module
• Pulse Generator modified to provide 50 Ohms, 5V drive
• Mini-360 Switching Power Supply
• 5V out
  • 7-23V in

Parts

GPS

• U-Blox NEO-7M GPS Module
• SMA Female connector

U-Center Programming Software

• U-Blox website
  • U-Center software
• Set to 8 MHz on GPS PPS pin when locked
  • Other frequencies have some "jitter"
• Set to 2 Hz on GPS PPS pin when not locked

FTDI

• FTDI-49MM

50 Ohm Driver

• Used modified PulseGen card to drive 50 Ohms, 5V level output
  • Remove oscillator circuit
  • 5 parallel 74AC14 outputs with 249 ohm resistors on each output
• Able to drive long 50 ohm coax
• Square wave output
• Very fast edges

Videos

• GPSDO vs Rubidium Frequency Standard