Generator Si5351a

Generator Si5351a

1MHz - 160MHz  GPS


Si5351a frequency generator is synchronized by1PPS signal from the GPS receiver.
Useful as a reference to 10MHz frequency meter, spectrum analyzer or other equipment, or as a stand-alone generator.
It is also a precision watch.


 The project is inspired by W3PM QEX July/August 2015 

GPS 2  GPS 3

After power on, the device checks the connection to the GPS receiver and then wait for the information about satellites.Then the time is displayed, and after 40 seconds if they are received all the necessary data  the frequency is synchronized.Time synchronization, information on satellites and frequencies repeated in cycles of 40sec.


The function Fstab shows us the last value of the frequency correction and the time remaining until the next synchronization. Observing it through now and again you will notice that the first adjustment when you turn it around 80Hz and then it was only + - 0.1Hz.

GPS 6  GPS 5

The output frequency is organized in five memory banks. Each of these memories can be freely programmed in the 1-160MHz range with an accuracy of 1 Hz. And the last menu item is the time zone. All functions are operated by encoder with a button.


How it's working:
We get 1pps impulses from the GPS module. For 40 seconds, we measure the 2.5Mhz signal coming from the Si5351a module. If no 1pps pulse is lost and the system counts all 40 pulses , the asterisk symbol appears on the display in the Fstab function and the output frequency is corrected. The correction value is the Fstab value in hz. If the frequency correction is less than 1Hz at least 3 times then its value is stored in the eeprom for faster correction after restarting.

The construction of the device is very simple.

Arduino NANO


GPS receiver any (in my quectel L80)


and 5V power supply


Schematic <>>>:



Soft<>>>: 02.12.2017r


The first time you start, you must perform EEprom initialization.
Press the encoder button and turn the power on.
The initialization tekst should appear on the display.