[time-nuts] Disciplining a Rubidium with a Thunderbolt.

[Will Matney]

Here's an app note from NASA on what they did for controlling, or
filtering, phase noise, and it can get complicated.

http://ipnpr.jpl.nasa.gov/progress_report2/XII/XIIK.PDF

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/12/2011 at 1:44 AM WB6BNQ wrote:

>Hi David,
>
>Just to clear the AIR, all Rubidium frequency standards have a crystal
oscillator as
>the primary signal source within the Rubidium device.  The Rubidium
portion of the
>standard is just a very high Q filter whose properties can be controlled
such that
>it's filter's center frequency has extremely small drift.  That small
drift factor is,
>typically, way less then the resulting factors that control drift in a
Quartz
>resonator.
>
>In order to gain the properties of the Rubidium's longer term stability
and the short
>term noise properties of a very good Quartz oscillator you would need both
items.  You
>select a very good Quartz device and phase lock it to a really good
Rubidium (with its
>own Quartz oscillator).  You would adjust the loop constants to correct at
a very slow
>pace consistent with the quality of the very good Quartz oscillator.
>
>To get to the next level (connection to the Nation's reference), you would
discipline
>the Rubidium against a GPS device with an even slower loop.  So, in the
end you have
>two separate loops with three separate devices.  This is not your "Nickel
& Dime
>store" plug-and-play set up.  It would have to be set up with care and
some
>experimentation to get it right.
>
>For a reference on the basic process, you should read the QST article on
Brooke
>Shera's GPS disciplined oscillator system.  Contained within it is a
description of
>the loop process I referred to above.  To utilize his method would require
upgrading
>his circuit design (some parts not available any longer) and some software
upgrading
>as well to account for those changes.
>
>To obtain the QST article go to Shera's web site at
http://www.rt66.com/~shera/
>Also click on the "more information line" for further reading.
>
>Bill....WB6BNQ
>
>
>"Dr. David Kirkby" wrote:
>
>> On 07/12/11 02:15 AM, Tim Tuck wrote:
>> > Hi all,
>> >
>> > Just wondering how many people have used John Miles work @
>> > http://www.ke5fx.com/tbolt.htm, or similar, to discipline a rubidium
>> > oscillator and if so...
>> >
>> > 1. what was the RB of choice ?
>> > 2.have any measurements of phase noise etc. been published on such a
rig ?
>> > 3. Are there any published how-to's etc. available ?
>> >
>> > I'd like to build such a beast as my lab standard so any help
appreciated.
>> >
>> > thanks
>> >
>> > Tim
>>
>> I'm no expert on this, but I believe that the rubidiums have poorer
phase noise
>> than crystals, so unless holdover performance is an issue, there is no
advantage
>> in using a rubidium over a crystal as long as GPS lock is maintained at
all times.
>>
>> The Stanford PRS-10 rubidium looks to be quite nice, as it has a 10 MHz
crystal
>> to give good phase noise and also the rubidium for medium term
stability. It can
>> be disciplined easily, as it has a 1 pps input.
>>
>> Alas the PRS-10 is not as plentiful (i.e. cheap) as some other
rubidiums.
>>
>> There may be better ways, but a PRS-10 and a timing receiver which
outputs 1 pps
>> looks to be a relatively easy way to get the short term peformance of a
crystal,
>> the medium term performance of a rubidium should the GPS get unlocked
and the
>> long term stability of GPS.
>>
>> I'm looking for a lab standard too, so I'd be interested in what other
replies
>> you get. For me personally, for a short term solution, I'm thinking of
using an
>> undisciplined rubidium.
>>
>> --
>> A: Because it messes up the order in which people normally read text.
>> Q: Why is top-posting such a bad thing?
>> A: Top-posting.
>> Q: What is the most annoying thing in e-mail?
>>
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