[time-nuts] Simple question I am sure

[Jim Palfreyman]

Hello,

Let me introduce myself. I've always been interested in time and more and more accurate clocks. I have built myself a GPS disciplined HP10811 clock (Murray Greenman's design) and it all works very nicely. I have acquired the old Australian "Speaking Clock" hardware and am driving it from my GPS clock. So it's "Pretty accurate". I broadcast the speaking clock output within a few 100m of home on FM 107.7 using a very lower power (hence legal) transmitter. A great hobby and impresses the friends.

However I have a general question and I don't really know the answer. And I bloody should!

If one of you walk into my workshop with your caesium clock and we plonk it down and make comparisons to my HP10811 clock we could compare the two, look at drift, phase noise etc. We would know the caesium is better and we would watch my clock drift with respect with that. No arguments.

So I walk into your workshop with black box A and compare it to your black box B. We have no idea whether either is a rubidium standard, a hydrogen maser or a wrist watch.

How do we know which is the more accurate timekeeper?

Keep in mind we have no other units to compare with. Only these two.

The reason for my question? How do we know when someone has invented a more accurate device to measure time?


Regards,

Jim Palfreyman


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