this arduino code controls a si5351 to keep the oszillation on a straight controlled level. the fathers ot this code is: Based on the projects: W3PM (http://www.knology.net/~gmarcus/) & SQ1GU (http://sq1gu.tobis.com.pl/pl/syntezery-dds/44-generator-si5351a) and the info found at http://sq7hjb.pl/index.php/mini-gpsdo/ of SQ7HJP

Copyright is maintained tho their code. my part added by oe6rke Robert ist following the same way: Permission is granted to use, copy, modify, and distribute this software and documentation for non-commercial purposes.

The code is using fixed qrg to supply an xtal of an rtl. Pinout and wireing is selfexplainary. if questions are left contact me oe6rke Robert, 2021-04

Following links were reused during this project: http://sq7hjb.pl/ http://sq7hjb.pl/index.php/mini-gpsdo/

http://knology.net/~gmarcus/Si5351.html http://sq1gu.tobis.com.pl/pl/index.php?option=com_content&view=article&id=44:generator-si5351a&catid=12&Itemid=107

https://github.com/etherkit/Si5351Arduino !!!

http://www.kh-gps.de/si5351.htm

si5351 frequency plan calculator https://emergent.unpythonic.net/01597601150

https://funduino.de/nr-42-oled-display-ssd1306-128x64-128x32

http://arduiniana.org/libraries/tinygpsplus/ https://github.com/mikalhart/TinyGPSPlus https://github.com/mikalhart/TinyGPSPlus/releases

https://www.rfzero.net/tutorials/si5351a/ http://www.hamskey.com/2018/03/how-to-use-si5351-1-source-analysis.html

http://arduiniana.org/libraries/tinygpsplus/ https://www.arduino.cc/en/Tutorial/LibraryExamples/SoftwareSerialExample https://forum.arduino.cc/t/softwareserial-with-nano/575224