01-01-2017, 12:29 PM
Crackle Wrote:This morning I put together the Pierce oscillator circuit, it took ages to find an RF choke of about the right value in my spares box, I stuck a bit of ferrite up it to help take the value to 2.5mH.
Hi Mike, I don't think the value of the chokes is critical, old compact fluorescent lamp electronic ballasts usually have a 1-5mH choke in them (every penny a prisoneer!)
If you just need to test for life signs, then Mark's idea of using a CMOS hex buffer is the way to go for both parallel or series crystals.
If you're getting a meter reading near the fundamental then they're good. As you say the crystals are old then don't be surprised that they are a bit off tune. The best types for long term frequency stability amongst the oldies are the Brook hermetic sealed glass encapsulated ones. The ones that are giving odd readings may be OK but are just not suited to the Pierce circuit.
Andy.
