Arduino NANO based 14 MHz frequency counter
Wanted to select four 10 MHz quartz crystals from a handful, to make a SSB filter. They need to be 40 Hz of each other. My HB frequency counter has a r esolution of 100 Hz and is useless for the task. A simple frequency counter with about 5 Hertz resolution should do the job. This counter should measure 14 MHz reliably. An Arduino NANO can be used to put together such a simple frequency counter. Time interval generation using internal ceramic resonator of Arduino was not preferred. An external 10 MHz quartz crystal oscillator was used instead. Though gate based quartz crystal oscillators are not very stable, a 74HC4060 oscillator / divider was used with a 10 MHz quartz crystal, for simplicity and lower component count. A 10 MHz OCXO was not available 😞 14 MHz frequency counter External signal ( of frequency F ) goes to base of Q1 via C. Q1 shapes the signal suitable for digital circuit. Shaped signal clock