[time-nuts] GPSDO Alternatives - Bert's boards

WB6BNQ wb6bnq at cox.net
Sat Dec 8 02:06:17 UTC 2012

Hello Bert,

The boards look nice but tell me nothing of the circuitry.  How about sending the schematics ??  That way I
can appreciate what it is that you have.

p.s.  By the way, what ever happen with that DMTD you were going to produce about three years ago ?

EWKehren at aol.com wrote:

> Attached is my latest ExpresPCB layout of a GPSDO. A clear  understanding
> of the GPS limitations, a goal as to what I want to control ,focus  on
> attainability, reproducibility KISS, cost and tests of partials on  development
> boards and what you see if you download the ExpessPCB software is on  the
> right the saw tooth correction, in the middle the analog board with opto
> isolation to prevent ground loop and on the right the actual GPSDO.  This
> particular unit also allows you to link a 20 Hz offset FRS-C (part of my dual
> mixer) to my house reference. Total material cost depending how many boards  one
> buys is below $ 40. I will include this particular board along with other
> designs on my next order and subsequently cut with a sheer.
> The board on the right could be used by itself with minor  modifications to
> directly drive a FE 5680 if some one would step up to the task.  Total cost
> below $ 15. I use the analog board, which by the way is the most  expensive
> since it has a LTC 1655 and REF 02.
> No dither 16 bits, dither 18 bits and depending on loop time,  clock
> frequency range starting at 3 E-9 and resolution up to 6  E-16.
> Again I am only interested in to controlling a Rb which gives  me way more
> flexibility, the Rb's are either modified with a 10811 or in  one case with
> the M1000 and in the case of the FE 5680 a MV89 with a separate  analog loop.
> And in all cases the RB is temperature  controlled.
> All this based on over 10 years of work with the Shera  controller,
> exclusively controlling Rb's.
> Bert Kehren
> One more thought you may want to look at a 1 $ gate array for  all your
> timing issues. Simplifies the work dramatically. With the long loop  times
> associated with Rb and high sample rate, 100 psec. are no  problem.
>   ------------------------------------------------------------------------
>                         Name: Shera 3 board.pcb
>    Shera 3 board.pcb    Type: PCB Wizard Document (application/x-unknown-content-type-PCBWizard.Document)
>                     Encoding: base64
>   ------------------------------------------------------------------------
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