[time-nuts] Primary Time Standards

[J. L. Trantham]

I am an extreme novice in this field but my understanding is that the
C-Field adjustments on the CS standards (5061A, 5061B that I am familiar
with) allow for insuring that the appropriate energy state transition of the
CS Ion is chosen as the 'reference' for the standard, something that can be
accomplished without 'calibrating' against another device.

The standard 5061A and 5061B provide a standard set of frequencies (5 MHz, 1
MHz, and 0.1 MHz for both the 5061A and 5061B and also 10 MHz for the
5061B).  I have never measured them against each other but I suspect their
phase will vary while their frequencies will be exact.  It is hard to
imagine that all CS ions are 'in phase' world wide.

The 5061A and 5061B both offer clock options that provide an indication of
time in an Hr:Min:Sec format as well as 1 PPS output.  There is also an
adjustment on these clocks to allow the 1 PPS to be synchronized with an
external 1 PPS such that the clocks can all be set to the same time +/- a
small error on the 'phase' of the 1 PPS.

If my understanding is incorrect, I would greatly appreciate being
corrected/educated.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Palfreyman
Sent: Wednesday, July 13, 2011 9:26 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Primary Time Standards


Hi All,

I've just realised I don't understand something. Something quite basic.

Primary Standards are ones which don't have to be calibrated against others.
My understanding is that Caesium and Hydrogen masers are Primary Standards
(in our field).

Secondary Standards are calibrated against the Primary Standards. My
understanding is that Rubidium is an example of a Secondary Standard.

So I can calibrate my Rubidium clocks by adjusting the C Field. All good.

But why is it that Caesium Clocks and Hydrogen Masers have an adjustment
facility?

And what about the clocks used to determine UTC around the world? Do they
have an adjustment facility? What are they adjusted to? Wouldn't that make
them Secondary Standards?

Now I'm aware that the "average" of those clocks is UTC, so are those clocks
adjusted regularly to get closer to that average?

I'm sure someone can clear this up for me.

Regards,

Jim
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