Frequency Calibration via GPS

Inexpensive Frequency Standard with output synchronized to GPS satellites,

Features

• Generates very accurate frequency output
• U-Blox NEO-7M GPS Module
• Remote Amplified GPS Antenna
• FTDI-49MM
• 50 Ohm Output

Parts

GPS

• U-Blox NEO-7M GPS Module
  • Programmable frequency from USB
• SMA Female connector
• 5V operation

U-Center Programming Software

• TP5 sets PPS output to "any" frequency
• U-Blox website
  • U-Center software
• Set to 8 MHz on GPS PPS pin when locked
  • Other frequencies have some "jitter" but are still GPS accurate
• Set to 2 Hz on GPS PPS pin when not locked

FTDI

• FTDI-49MM

50 Ohm Driver (Not Required - nice to have)

• 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

• This is the approach I followed

• GPSDO vs Rubidium Frequency Standard