[time-nuts] Chinese GPSDO 10 MHz error

[Mike Feher]

Look in the manual for the 8640B as they use FLL there when the lock button is pushed on the front panel. Simply, in one case, in lock, the numbers driving the frequency readout is saved and then when the oscillator drifts one way or the other, an EFC is applied that attempts to make the new readout driver number equal to the saved number. Regards - Mike 

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Benward
Sent: Wednesday, August 26, 2015 11:55 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Chinese GPSDO 10 MHz error

So how does a frequency lock work?  How is it implemented? Can someone sketch a schematic?

And what equipment or technique is used to measure a 2hz error at 100GHz?

Bob

>>> -----Original Message-----
>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Tim 
>>> Shoppa
>>> Sent: Wednesday, August 26, 2015 5:18 PM
>>> To: Discussion of precise time and frequency measurement
>>> Subject: Re: [time-nuts] Chinese GPSDO 10 MHz error
>>> 
>>> Full KE5FX evaluation of BG7TBL GPSDO here:
>>> http://www.ke5fx.com/gpscomp.htm
>>> 
>>> I'm wondering out loud if it might, like many hobbyist GPSDO's, be 
>>> frequency-locked rather than phase-locked and thus susceptible to 
>>> last-digit- counter bobble in some long-averaging counter.
>>> 
>>> Tim N3QE
>>> 
>>> On Wed, Aug 26, 2015 at 3:18 PM, Perry Sandeen via time-nuts < time- 
>>> nuts at febo.com> wrote:
>>> 
>>> > Hi,
>>> >
>>> >
>>> >
>>> > On the EEVBLOG  (http://www.eevblog.com/forum/index.php)
>>> >
>>> >
>>> >
>>> > They mention that the "2014-11-06"version GPSDO that was “most 
>>> > extensively tested, so far (by ke5x and others).
>>> >
>>> >
>>> >
>>> > (Has a) known bug, outputfrequency is not exactly 10mhz
>>> > (9,999,999.999,800 Hz). This translates to ~2hzerror at 100ghz.”
>>> >
>>> >
>>> >
>>> > A question is if this bug isjust for this particular model or all 
>>> > other versions suspect?
>>> >
>>> >
>>> >
>>> > I realize that in and of itsself it is very small error, but 
>>> > errors tend to multiply or cause incorrectconclusions to testing.
>>> >
>>> >
>>> >
>>> > Another question is will the LHdisplay unit they offer work with 
>>> > other Trimble units such as are offered byRDR?
>>> >
>>> >
>>> >
>>> > That said, these models seem tobe a very nice turn-key systems.
>>> >
>>> >
>>> >
>>> > Regards,
>>> >
>>> >
>>> >
>>> > Perrier
>>> >
>>> > _______________________________________________
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