[time-nuts] First success with very simple, very low cost GPSDO, under $8

Brian Lloyd brian at lloyd.com
Thu Apr 10 11:28:55 EDT 2014

On Wed, Apr 9, 2014 at 11:43 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> > You are right in the I don't even need data cycles.  All I want is the
> > error which is 5,000,000 minus the count.  this is hopefully zero.
> Correct. Keep the counter running. No need to zero it, ever. Use
> differential measurements. Essentially you are using binary modulus
> arithmetic.

Chinese remainder theorem. Use that and stop worrying about how big your
word is. Since we have these really great integer divisors we can use
between 1e7 and 1e0, it becomes trivial. Your counter word only needs to be
large enough to handle the maximum possible accumulated error in an
interval. In fact, you probably can get by comfortably with an 8-bit

Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian at lloyd.com

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