Crystals

[Ed Richards]

A crystal frequency depends on the impedance of the oscillator circuit.
Perhaps the off-frequency ones were ground for a different impedance. 32
pf is more or less a standard shunt capacitance, although others are
used. All commercial gear that I have worked on (hundreds) use a variable
capacitance or inductance to set the frequency right on. Try varying the
Z of the circuit and see if the crystal will come on frequency.

Ed Richards

On Wed, 17 May 2000 21:24:49 -0400 Bill Coleman AA4LR <aa4lr at RADIO.ORG>
writes:
> On 5/16/00 10:35 PM, Edward Gardner at egardner at TWCNY.RR.COM wrote:
>
> >Anyone know how to check crystals to see if they are working? I
> realize
> >they probably have to take quite a jolt to STOP working, but I've
> got one
> >that may have come from the factory bad.
>
> Plug them into a crystal oscillator. The ARRL handbook has several
> simple
> circuits for doing this.
>
> I homebrewed up one such circuit, and tested a whole bunch of
> FT-243-type
> crystals I had. Out of the bunch, only 1 wouldn't oscillate,
> although
> several were up to 5 kHz off of their marked frequencies.
>
>
>
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at radio.org
> Quote: "Boot, you transistorized tormentor! Boot!"
>             -- Archibald Asparagus, VeggieTales
>
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