Using 4 surplus Lucent rubidiums compared to a Lucnet GPS receiver I find a
consistent error of between 110 and 860 pico-seconds using a HP 5370B after
running them for about two weeks. By measuring the weekly drift one could
calculate the drift. I measure the offset at about 20 milli-Hz.
To phase lock it use the NIST 60KHz by diving it down to 10KHz and using the
comparator circuit used by James Miller G3RUH in his Rockwell GPS circuit for
10MHz crystal oscillators.
You’d probably want to inhibit the circuit during the two periods between dawn
and dusk to avoid what I believe is called the diurineal (sp) shift. In that
small amount of time the Rb oscillator shouldn’t drift out of spec.
There was a circuit published in 73 magazine called “the worlds most accurate
clock” and a PC board kit for it is available from FAR circuits. There was
also a similar one published in Ham Radio magazine in the 70’s IIRC.
10 foot diameter loop antennas made out 3/4 inch PVC pipe and orientated
towards Boulder, CO would give reliable reception and are inexpensive to make.
Total cost is less than $800. The trick is borrowing a TIC for set up.
Hope this might help.
Regards,
Perrier
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