Dear LF group,
Looking through my box of crystals recently, I found some
operating in the range 30 - 40kHz. They are in glass envelopes,
and I noticed that the metalisation on each side of the quartz plate
is divided into two halves, giving four electrodes. On some units, all
four electrodes are connected to seperate pins, while on others
two diagonally oposite electrodes are commoned, giving only 3
external connections. They look a little like 2 pole monolithic crystal
filters, but have no bandwidth marked on them, and I have not
heard of such filters being used at low frequencies.
Does anybody know how these 3 and 4 terminal crystals are
used? Just curious really.
Cheers, Jim Moritz
73 de M0BMU
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