W2ETI Frequency Reference
If you have one watch, you know what time it is. If you have two that
disagree, you can't be sure. So with watches, so with frequency standards,
which are really just very good watches. I put together a triple standard
to always be sure:
- A rubidium (Rb) atomic standard, which should be correct to parts in 10^11.
However, there is no long-term correction, and, of course,
something can go wrong.
- A GPS receiver with an ovenized quartz oscillator whose frequency is
"disciplined" by the GPS. Because GPS is monitored and corrected by
the people in charge of time, bizarre as that concept may seem, its
long-term accuracy is "perfect." Its short term accuracy is usually
parts in 10^11 as well, although if the GPS signal is lost it can
- A high-quality ovenized quartz oscillator, whose frequency is adjusted
by screwdriver instead of by quantum mechanics or the government.
Oddly, this is probably the most stable and cleanest oscillator, short-term.
But it can and does drift, by about 1 part in 10^9 over a couple of weeks.
Behind this unassuming panel is one of each. If the GPS and Rb
disagree, the quartz can decide which is right.
Why no detailed internal photos?
Next time I take it out of the rack I'll take some and add them here.
Meanwhile, visualize whirling satellites and tiny quantum mechanics vibrating