Having developed several systems based on this principle, I am now pleased to offer the design illustrated on this page which incorporates the best results of my experience of the Jupiter GPS engine, phase-locked loops and OCXOs. With careful choice of components, patient sourcing and rational design I have been able to keep the price at level affordable by the small commercial or home laboratory and by serious radio amateurs. Read an independent comparison of several GPSDOs.
The frequency accuracy is of course set by the GPS idiom, and is essentially exact for practical purposes. The stability as given by the Allan Deviation is typically 5x10-12 at τ=10s. That figure is 0.05 Hz at 10 GHz and is a remarkably small value.
The low phase noise from the high-quality OCXO results in a very clean 'sound' to harmonics in the microwave region, and with a power consumption of 300 mA at 12.5V this GPSDO is suitable for field operation from a car battery.
Other applications include radio beacons, harmonic marker 'comb' generators, downconverter and test equipment external frequency reference.
Specification
Power Input
Voltage min: 12.5V DC
max: 18.0V DC
Current min: 0.3A
max: 0.6A during OCXO warm up (about 2 minutes)
Connector: Screw terminal block
GPS Receiver
Rockwell Jupiter TU30-D140-221
Connector: MCX socket
Socket powered 5V for active antenna (this can be disabled)
LED shows 1PPS (1 pulse-per-second); synced to UTC when RX locked
Signal Output
10 MHz sinewave, AC coupled
Level: 13 dBm into 50Ω ; 1V RMS
Connector: BNC
0-5V or ±2.5V square-wave on request
Data Input/Output
RS-232 in/out of GPS receiver
Protocol: NMEA (user changeable)
1PPS on DCD line
Connector: DE9S
Warm-up Accuracy
After 30 minutes < 10-10 typical
After 60 minutes < 10-11
RMS accuracy (over a 10s period)
7x10-12 ; that is, 99% of measurements would fall within ±2x10-11
Stability (Allan deviation) typical
1s < 1x10-12 1000s < 2x10-12
10s < 3x10-12 10000s < 3x10-13
100s < 5x10-12 1 day < 5x10-14
Dimensions
35 H x 92 D x 150 W mm including mounting flange
Weight 0.430 kg
- Supplied with 80cm power cable with 6mm spade terminations.
- Full documentation.
- Built, tested and ready to use (that is, not a kit). Just connect your GPS
antenna, apply 12V DC power and you're in business.
Price
The price of this GPSDO and shipping is:
OCXO-based GPSDO, part No. 0091-000 £240
Shipping by secure service: UK £10
EU/US/AUS etc £15 (via air-mail)
Kindly note that I am unable to supply GPS antennas, power supplies or kits of parts for this product.
Prior GPSDO developments with emphasis on self-construction.
Last updated: 2008 Mar 25