This small board is used throughout my transverters due to its simplicity and versatility. It uses an SI4133G-BT RF synthesizer chip which locks to an external frequency reference (I use a GPSDO). An ATtiny13A microcontroller is used to program the SI4133 each time it powers up and to detect whether it is locked (and producing the desired frequency output) or not . You will find a link here where you can download some useful files including the PCB and an example program written in Bascom-AVR. The document is still in a draft stage (as of 12-2-2013) and it will be expanded with more information in the near future.