Hamshop.cz

There are cheap boards with ADF4351 34MHz to 4.4GHz Frequency Synthesizer available on eBay or Aliexpress.

With this simple board you can set registers in PLL and program PLL to you frequency. You can make an easy signal generator or personal beacon for ham radio bands, or use it as LO (local oscillator) for a transverter.

The KIT contains all parts and the MCU is not programmed. There is source code available on github and program can be compiled with Arduino IDE.