[time-nuts] Disciplining Rubidium

J. L. Trantham jltran at worldnet.att.net
Thu Apr 24 11:20:34 UTC 2008


Thanks,

That helps immensely.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Tom Duckworth
Sent: Wednesday, April 23, 2008 10:58 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Disciplining Rubidium

Joe,

tau, the Greek symbol for a defined measured time (1 sec., 10 sec., etc.)
when using it in a timing application measurement. In nuclear physics it has
a very different meaning (weakly interacting subatomic particle).

Tom
Tom Duckworth
510-886-1396
 
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of J. L. Trantham
Sent: Wednesday, April 23, 2008 8:15 PM
To: wa1zms at att.net; 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Disciplining Rubidium

I have truly enjoyed 'reading the mail' on this group.

However, I need some help or a 'refresher' on the lingo.

I am a Clinical Cardiac Electrophysiologist but in a bygone millennium, I
received a BEE and a MSEE from Georgia Tech before I went to Medical School.

'tau'?

Thanks,

Joe
WB4BPP

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of wa1zms at att.net
Sent: Wednesday, April 23, 2008 7:37 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Disciplining Rubidium

But doesn't it matter what your definition of "short term" really is?

I have some Wenzel OCXOs that hit 5E-13 for a 1 second tau. No Rb or Cs
or Z3801 that I have running get that good at 1 sec tau!  Over 10,000
is a different matter, however.


-Brian, WA1ZMS

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Tom Duckworth
Sent: Wednesday, April 23, 2008 6:13 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Disciplining Rubidium


Antonio,

Absolutely! With a good XTAL you have parts in the 9th, short term. With a
XTAL controlled by a Rubidium, in the phase-lock feedback loop, you have
parts in the 12th, short term. With the Rubidium disciplined by the GPS,
with its on-board Rubidium/Cesium oscillators updated from the ground every
orbit, you have parts in the 14th, short term. In other words, your
XTAL/Rubidium/GPS has an effective short-term Allen variance equivalent to a
good Cesium; and better than a single Cesium, long term, for a lot less
money!

Tom
Tom Duckworth
510-886-1396

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of iovane at inwind.it
Sent: Wednesday, April 23, 2008 3:11 PM
To: time-nuts
Subject: [time-nuts] Disciplining Rubidium

Does it make any sense "GPS disciplining" a rubidium oscillator?
In such a case we have a chain made of
GPS - Rubidium - XTAL
as opposed to the simpler case of
GPS - XTAL
(assume that XTALs are of the same quality, and so the control loops).
Does the addition of Rb in the middle of the chain add
any real advantages?

Antonio I8IOV



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