The GPS Disciplined Reference Generator GPSD-2 is designed to provide accurate and stable frequency locking for microwave digital phase locked loops, VHF/UHF radios, and test equipment. Four sine wave outputs are provided. The module operates over a wide range of supply voltages. Once calibrated by GPS disciplining, the GPSD-2 module maintains the same accuracy and stability as its OCXO module and will hold its calibration for up to 12 months.

The module is based on a CTI OSC5AB02 oven-controlled crystal oscillator OCXO, square wave, operating at 5V. The inherent OCXO has a warm-up time is less than 2 mins and stability is better han 10 ppb (±0.1Hz) at 0^oC to 45^oC. Phase noise is -80dBc/Hz@1Hz, -120dBc/Hz@10Hz, -140dBc/Hz@100Hz, -145dBc/Hz@ 1kHz, -150dBc/Hz.

The module may be configured for sine or square wave outputs of more than 0 dBm. Four SMA outputs are available along the back panel of the enclosure.

The GPSD-2 uses a u-blox GPS receiver and an Arduino Nano microprocessor to supervise and discipline the highly stable OCXO.  

The module operates from a supply of 12 to 28V dc. At 12V the current drain at start-up is less than 0.6A. When settled, the current drain at 12V is less than 300mA and at 26V is less than 200mA.

The GPS receiver warm starts in seconds after which the precision 1PPS pulse is used to measure the frequency of the OCXO. After a few minutes delay for warm-up, the EEPROM stored is applied to set  the OCXO to frequency. The frequency is then measured over 30 second intervals and, if necessary, corrections applied to correct the accuracy. After the initial warmup time, the frequency is measured over longer periods and fine corrections applied, if required. These small corrections will not affect the performance of digital protocols.

The status of the GPS disciplined OCXO is displayed on four LEDs:

• Power (Green) indicates unit is operating;
• 1PPS (Blue) indicates GPS receiver is locked and producing 1PPS timing pulses;
• Warn (Red) is lit steady during timed warm-up and flashes long during coarse discipline, then fast during fine discipline, and then goes out when accurate and stable ± 0.1Hz (± 10ppb);
• OK (Green) indicates the reference is GPS locked.

The GPS is configured to send NMEA sentences at 9600 baud via serial USB on the processor and quasi-RS-232 via a 3.5mm phone jack. The RMC, GGA, and GSV sentences may be connected to a personal computer for time synchronisation, grid square calculations, or beam headings. The RS-232 will synchronise radios such as the IC9700 for time and position.

Enclosure is an aluminium extruded enclosure 120 x 85 x 40 mm.

For What makes GPSD-2 Different?   See https://vk4amg.blog/what-makes-gpsd-2-different/