[time-nuts] FE-5680A Mechanical Question

EWKehren at aol.com EWKehren at aol.com
Thu Jan 12 11:20:51 EST 2012


I have experimented with it find that to take advantage of the OCXO you  
should use its full potential which means long time constant and I was not 
able  to get good results. It would have saved a loop but I would not interfere 
with  the 5680 internal loop because we do not know how it performes.
Bert Kehren
 
 
In a message dated 1/12/2012 11:16:18 A.M. Eastern Standard Time,  
azelio.boriani at screen.it writes:

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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