[time-nuts] FE-5680A Mechanical Question

Azelio Boriani azelio.boriani at screen.it
Thu Jan 12 11:15:43 EST 2012


A good OCXO left alone. Rbs should have OCXOs inside...

On Thu, Jan 12, 2012 at 5:01 PM, John Ackermann N8UR <jra at febo.com> wrote:

> I think you have to define "better," though.  A GPSDRbO will have better
> holdover performance (e.g., stability when the GPS signal goes away) than
> one using an OCXO, but the OCXO is quite likely to have better short term
> stability than the Rb.
>
> If holdover isn't an issue, you need to find the "Allan Intercept Point"
> (term stolen from David Mills and NTP) to see where the GPS and oscillator
> ADEV curves cross over.  That will tell you how long a loop time constant
> you want, and will let you look at the combined ADEV for each type of
> oscillator.  You may find that a decent OCXO gives better performance
> overall than an Rb.
>
> John
> ----
>
>
> On 1/12/2012 10:37 AM, EWKehren at aol.com wrote:
>
>> with the good long term performance of Rb's and the presently available
>> 5680A for $ 40 a Shera Type controller will make available to any one on
>> the
>> list a reference better than a Tbolt for less money than a Tbolt.
>> Repeating
>> my  self I would also add a "clean up" OCXO in order to get the very best.
>> Bert Kehren
>>
>>
>> In a message dated 1/12/2012 8:34:54 A.M. Eastern Standard Time,
>> jltran at att.net writes:
>>
>> David,
>>
>> I have been following discussions on the list about a  GPSDRbO for a year
>> or
>> so.  Some interesting challenges and probably  best implemented in a
>> 'stable'
>> environment rather than portable operation  but as best I can tell, it
>> would
>> require a very stable and good antenna  location, stable and clean power,
>> and
>> I was thinking of using something  like an LPRO-101 with an Ext C Field
>> input, a Shera type controller, and a  GPS timing receiver, though, I
>> suspect
>> there are likely to be some  'multi-tasking' receivers out there that will
>> look at several sources  including GPS, GLOSNASS, etc.
>>
>> While the project might be fun, for  portable work, it is likely far
>> easier
>> and probably just as good (almost),  to use a Tbolt.
>>
>> In any event, something to think about for the  future.
>>
>> Joe
>>
>> -----Original Message-----
>> From:  time-nuts-bounces at febo.com [mailto:time-nuts-bounces@**febo.com<time-nuts-bounces at febo.com>]
>> On
>> Behalf Of  David
>> Sent: Wednesday, January 11, 2012 11:12 PM
>> To: Discussion of  precise time and frequency measurement
>> Subject: Re: [time-nuts] FE-5680A  Mechanical Question
>>
>>
>> How would a GPSDRbO work?  Phase lock the  DDS output to the GPS? Phase
>> lock
>> a VCXO to the GPS and then phase lock to  the RbO on loss of GPS lock?
>>
>> On Wed, 11 Jan 2012 22:55:58 -0600, "J. L.  Trantham"<jltran at att.net>
>> wrote:
>>
>>  Bill, Brian, Bill, and  Peter,
>>>
>>> Thanks for the info.  All I need now is a 'project'  to incorporate the
>>> unit into.
>>>
>>> In the back of my mind, I  have the thought of a 'box' that will be
>>> battery powered or 110 VAC  powered (perhaps with an internal SLA
>>> battery) and include a GPSDO and  Rb unit (possibly a GPSDRbO) for the
>>> purpose of a 'reference' for  portable operation in the microwave
>>> regions.
>>>
>>
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>
>
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