[time-nuts] Fw: New to list and GPSDO questions

[Bob Stewart]

OK, I believe you.  I can see I have a lot to learn.

Bob



----- Original Message -----
> From: Richard H McCorkle <mccorkle at ptialaska.net>
> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com>
> Cc: 
> Sent: Thursday, June 13, 2013 7:04 PM
> Subject: Re: [time-nuts] Fw:  New to list and GPSDO questions
> 
> Hi Bob,
> Any user of a Brooks Shera controller will tell you that phase errors
> can be recovered using a jittery 1PPS reference. While the 1PPS may
> jitter (+/- 42ns in a UT+ GPS) the jitter averages out to zero error
> over time. The Shera controller uses the phase difference between the
> 1PPS and divided by 16 source to drive the EFC to maintain a constant
> phase difference. The Shera design updates every 30 seconds and in
> mode 1 the phase error from setpoint is sent directly to a DAC to
> correct the frequency. Shera adds a selectable filter before the DAC
> to reduce the EFC noise and increase the correction stability. More
> samples averaged over a longer period increases the stability, but
> smaller corrections are applied over a longer period to make the
> phase (frequency) correction.
> 
> Richard
> 
> 
> 
>>  Hi Richard,
>> 
>>  As time goes by, I'll reread your post until I understand it.  I'm 
> a newbie, but
>>  It's hard to believe that there is enough information in a jittery 1PPS 
> reference
>>  pulse to be able to recover phase errors.
>> 
>>  Bob
>> 
>> 
>> 
>>  ----- Original Message -----
>>>  From: Richard H McCorkle <mccorkle at ptialaska.net>
>>>  To: Bob Stewart <bob at evoria.net>; Discussion of precise time and 
> frequency
>>>  measurement <time-nuts at febo.com>
>>>  Cc:
>>>  Sent: Thursday, June 13, 2013 5:51 PM
>>>  Subject: Re: [time-nuts] Fw:  New to list and GPSDO questions
>>> 
>>>  Hi Bob,
>>> 
>>>  The VE2ZAZ controller is a frequency locked loop that keeps the source
>>>  on frequency but over time the phase drifts, as past corrections are
>>>  not compensated for.
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>