[time-nuts] 10MHz Rubidium reference source for frequency counter

Magnus Danielson magnus at rubidium.dyndns.org
Sun Oct 26 18:14:21 EDT 2014


Hi Brooke,

I wonder which instruments that would be, as most of them calibrate 
easily standing flat on the bench.

Cheers,
Magnus

On 10/26/2014 11:01 PM, Brooke Clarke wrote:
> Hi Magnus:
>
> I've also heard that in order to calibrate rack mount crystal
> oscillators in instruments they need to be in the same orientation as
> when mounted in the rack.  So you can not remove the instrument from the
> rack and turn it on it's side for the cal.  So for some instruments that
> means mounting them in an empty rack and laying on your back like
> working under a car.
> Mail_Attachment --
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> http://www.prc68.com/I/DietNutrition.html
> Magnus Danielson wrote:
>> Brooke,
>>
>> 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. :)
>>
>> Cheers,
>> Magnus
>>
>> 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:
>>> http://www.prc68.com/I/ThunderBolt.shtml
>>>
>>> Another crystal based GPSDO is the HP Z3805:
>>> http://www.prc68.com/I/Z3805A.html
>>>
>>> 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.
>>> http://www.ebay.com/itm/171504585820
>>>
>>> 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.
>>> http://www.prc68.com/I/PRS10.shtml
>>>
>>> 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
>>> http://www.PRC68.com
>>> http://www.end2partygovernment.com/2012Issues.html
>>> http://www.prc68.com/I/DietNutrition.html
>>> Karen Tadevosyan wrote:
>>>> Hello All,
>>>>
>>>>
>>>> Can I have your recommendation regarding a choice of 10 MHz rubidium
>>>> source
>>>> (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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