[time-nuts] GPSDO Alternatives
EWKehren at aol.com
EWKehren at aol.com
Fri Dec 7 22:38:35 UTC 2012
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.
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.
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