mike742 wrote:
I've always noted with some curiosity that 77.503kHz,
60.002kHz, and 60.005kHz are off-the-shelf crystals too...
used in a direct conversion receiver for DCF/WWV to 3Hz, 2Hz,
and 5Hz carrier-detect frequencies maybe?

Strange. Maybe another resonance mode?

I'd guess the specified frequency is parallel resonance with
the specified load capacitance.

I have some Digi-Key SE3320-ND 60 Khz xctls (C-2 60.000KC-P).

My best try at measuring the series resonant frequency shows
59998 Hz. Perhaps the 60.002 Khz ones are series resonant at
60000 Hz. I don't have any of those to measure.

Here are some measurement of a few Epson Type 2 60 kHz crystals I made
recently:

Fs BW Fp
60001.6 4.6 60009.9
60001.2 4.6 60009.7
60002.2 5.6 60010.6
60001.1 4.4 60009.5

The test setup is shown below. The input signal was produced
by my homebrew function generator implemented with an AD9833.
The clock for the 9833 is an 10 MHz SG-615B which
has a specified frequency stability of 100 PPM.


|Vcc
|
|
20.0k |
Vi 0.1++ |-+ 2N5457
-/\/\-+--||-||--+-|
| ++ | |-+-- Vo
\ \ |
/ 1M / \
1.0k \ \ /1k
| | \
| | |
+---------+----+
|
V