[time-nuts] 10MHz Rubidium reference source for frequency counter
magnus at rubidium.dyndns.org
Sun Oct 26 21:51:32 UTC 2014
One use for the R variants of the Fluke/Pendulum counters is/was for
calibrating base-stations. They had issues with ovens and turning the
counter to the side as you lifted it up. A rubidium inside solved that
in a nice way.
It's not all government work you know. :)
On 10/26/2014 10:45 PM, Brooke Clarke wrote:
> Hi Karen:
> The ones you mention are all stand alone Rb oscillators that need to be
> calibrated to set their frequency.
> This was the historical way that crystal oscillators were calibrated
> every year or so. The great advantage of Rb over crystal oscillators is
> that their drift is specified in months instead of days.
> A much better - more modern idea - is the GPS Disciplined Oscillator
> (GPSDO). It keeps the oscillator "calibrated" in real time.
> A popular crystal based GPSDO is the Trimble ThunderBolt:
> Another crystal based GPSDO is the HP Z3805:
> There are many more commercial GPSDOs and this list has discussions that
> show they can be a do it yourself project for under maybe $10, but
> require a number of sophisticated skills.
> I have the just released LTE-Lite GPSDO Evaluation Kit with 10MHz TCXO
> on order. Seems to offer good performance for the dollar.
> The only advantage of a Rb GPSDO over a crystal GPSDO is for the case
> where the GPS updating has not happened for some time.
> This might be due to a power failure lasting some days or that the
> oscillator will be used where there's no GPS access and it only gets
> "calibrated" then used much later.
> The Stanford Research PRS-10 Rb oscillator can be used stand alone where
> it time stamps an external 1 Pulse Per Second input, or as part of a
> GPSDO where an external GPS receiver supplies it with a 1 PPS input.
> The Thunderbolt can be custom modified to drive an external Rb
> oscillator, like the ones you mentioned, but that requires some
> technical sophistication.
> Note the ThunderBolt and Z3805 are complete GPSDOs in a box, just
> connect power and a GPS antenna.
> The PRS-10 requires an external GPS receiver and antenna. A a practical
> matter that means it's more work to maintain the PRS-10 because there's
> more opportunity for problems like disconnecting a cable.
> PS Stanford Research offered a version of their SR620 Time Interval
> counter that included a Rb oscillator (not a GPSDO) that some government
> agencies purchased, but for normal use you really don't need a Rb
> oscillator, so the CNT-91R appears to be a similar way so sell it to a
> government with a lot of money to spare. So don't feel pressured to use
> an Rb oscillator. http://www.prc68.com/I/TandFTE.shtml#SR620
> Mail_Attachment --
> Have Fun,
> Brooke Clarke, N6GCE
> Karen Tadevosyan wrote:
>> Hello All,
>> Can I have your recommendation regarding a choice of 10 MHz rubidium
>> (available now on eBay like FE-5680; LPRO-101; LPFRS; FRS etc.) as a
>> reference signal for my frequency counter Pendulum CNT-91.
>> Thanks in advance.
>> Karen, ra3apw
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