Hello Tim,

Of the longwave radio frequencies used for time standards, 40kHz (JJY,
Japan), 77.5kHz (DCF, Germany) and 60 kHz (WWVB and MSF) crystals are
off-the-shelf items in the Digikey catalog at less than a dollar each.
I'm guessing their easy availability is because they are commonly used
in real receivers.

Yes, but if these crystals are the only thing you'd have to buy right
now that would easily become $10 with S&H. Or about half of what an
atomic clock is at the discounters and there the price includes a huge
display along with the receiver parts.

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?

Regards, Joerg

http://www.analogconsultants.com