I recall someone making a very narrow CW filter (20Hz?) which utilised a number of 32kHz clock crystals. I'd like to have a go at building one but can't recall where I saw the information. Can anyon
Its was I ........... 1) Take a handful of watch crystals, from the same batch (buy 10 or 20 from Farnel / Maplin ??) 2) Connect 5 in series to form the top elements of a ladder filter; you now have