Precision Frequency Reference (GPS Clock)

Price: 150.00GBP



Low-jitter GPS-locked precision frequency reference
450 Hz to 800 MHz output

This device outputs two synchronised low-jitter reference clocks locked to GPS signal.

Long term stability of output signal is defined by high accuracy of GPS Caesium references and theoretically approaches 1x10-12.

Short term signal quality is defined by internal TCXO clock source providing high-quality, low phase noise clock signal with sub-picosecond RMS jitter.

Digital PLL allows main output reference frequency to have almost any value between 450Hz and 800MHz.

Two outputs can be individually enabled and set to different frequencies. Second output frequency depends on the first output. If both outputs have the same frequency their relative phase shift can be adjusted. This can be used, for example, to generate two signals with 90° phase shift for use in I/Q mixer.

Both output signals are at 3.3V CMOS levels with 50 Ohms characteristic impedance. Their output drive levels can be adjusted.

Output power level (measured at 10MHz, fundamental power channel):
+13.3dBm, drive setting 32mA
+12.7dBm, drive setting 24mA
+11.4dBm, drive setting 16mA
+7.7dBm, drive setting 8mA

Operation requires continuous presence of GPS signal, however temporary loss will be tolerated seamlessly. Active or passive antennas are supported. An active antenna with 3 metre cable is provided with the device but can be substituted if necessary. GPS acquisition time after power-up is around 30 seconds. If GPS signal is lost, digital PLL will maintains best estimated output frequency based on historical data. On reacquisition of GPS lock, output is seamlessly brought back in sync with GPS reference. Entry and exit of frequency hold is glitch-less.

All frequency and output settings are fully user-configurable via USB connection from Windows PC.

GPS clock can be powered from USB input and/or external 5-15VDC power input including standard +13.8V PSUs or car battery. USB connection to Windows PC is required only for one-off configuration. All settings are stored inside the device and maintain values when off.

Examples of use include:
 10.000MHz, 1.000MHz or other frequency reference for lab equipment and instrumentation
 reference for transmitter equipment - HAM rigs, propagation beacons, frequency markers
 reference for receiving equipment, RTL SDRs (28.8MHz) and band scanners
 calibration source for radio receivers
 master clock for audio and video equipment, DACs and studio recording gear

Measured phase noise of standard (TCXO) version is equal or better than

-120 dBc/Hz at 100 Hz
-133 dBc/Hz at 1 kHz
-137 dBc/Hz at 10 kHz
-140 dBc/Hz at 100 kHz
-144 dBc/Hz at 1 MHz

We are happy to advise whether specific combination of output frequencies are achievable and preset them into the product before shipping. If you are not happy with your product for any reason just send it back and we will refund your purchase. Please contact us at if you have any questions.

SDR-Kits has selected the Leo Bodnar precision GPSDO as the recommended External Reference Oscillator for the DG8SAQ Vector Network Analyzer

This product is available in USA from AirSpy.US

Links :
21 page GPSDO Technical Evaluation Report By OZ7OU: HERE
An Informal Evaluation of a Leo Bodnar GPS Frequency Reference By W.J.Riley: HERE

Phase noise plots have been acquired with HP E4406A signal analyser using notch filter method. The measured phase noise approaches the noise level of E4406A and therefore might be lower than presented here.

Connect the device to a PC via the supplied USB cable. Configuration software can be downloaded from the Product Downloads tab.

Open the software and set the desired frequency. You can find PLL setting by putting required freq in "Output 1" window and clicking "Find".

Then save it in the clock hardware by clicking "Update". If you want independent frequencies, adjust the PLL parameters (below Output2) manually and click "Update".

"Sleep" button shuts down internal micro controller for lowest noise level. It requires power cycle to wake it up again.

It does not need any drivers installed or even USB connection. You can use external 12V power supply without USB attached.

Configuration Software - Click Here to Download

Latest Firmware - version 1.09 - Click Here to Download

Quick use guide

1. Put frequency in output 1 field

2. Click “FIND”

3. There is no step 3.

On the power supply connector, which pin is the +ve and what is the recommended voltage?

Centre pin is "+" supply voltage is 5-14v voltages. Any excess voltage over 5v will be converted to heat, so it is recommended to use closer to 5v.
The case can become warm to the touch ( 40°c ) at high voltage levels ( 12v + ) this is normal operating.

What are the differences between the two different models offered for sale?

The 'Optional Crystal' unit has a crystal instead of a TCXO as the system clock source. It has a slightly lower phase noise in the close range ( 1kHz ), in exchange for higher drift in the unlocked state and longer lock times.
This option should only be considered if you definitely know that phase noise has to be as low as possible.

How do I tell if the unit is locked onto a GPS signal?

The two status LEDs on the front of the device will be constantly on.
Also if the device is connected to the software the two warning messages will not be show.
'No PLL Lock' and 'No GPS Signal' will be shown if there is a problem connecting to the GPS signal.

What do the two LEDs mean?

The LEDs will flash when the clock is searching for a GPS lock and remain constantly lit when GPS lock is successful.

In the software, what does Signal Loss Count mean?

Signal Loss Count is an indicate or counter of how many times the signal has been lost since power up. If you leave the unit unattended it might be useful to know if it had lost the signal while you were away and how many times this happened.

When I hit FIND or UPDATE on the software No PPL lock is displayed and then disappears. What does this mean?

Every time you program new frequency or update the old one by clicking the buttons "Find" or "Update" the system then recalibrates itself. This causes a temporary loss of lock for a few seconds. This is normal and only happens during frequency changes.