[time-nuts] Weird GPSDO behavior
shalimr9 at gmail.com
Fri Sep 29 09:47:20 EDT 2017
It makes me feel better (not good, just better) to know it's not just me...
On Sep 29, 2017 7:19 AM, "Bob kb8tq" <kb8tq at n1k.org> wrote:
> > On Sep 28, 2017, at 6:59 PM, Mark Sims <holrum at hotmail.com> wrote:
> > I suspect that it is either temperature related (the funkiness starts
> around when the temperature reaches a minimum) or related to the way the
> disciplining parameters are hacked to get the extended time constant.
> Like it or not, most of these devices were made back a while ago.
> The CPU’s used were not the ones we have today. the code was tested
> over the “expected range” of values. Most (but not all) of the control loop
> code was done as integer math. With limited RAM, tossing everything into
> 64 or 128 bit integers was not an option. In some cases 32 bit int’s were
> a premium. Multiply this by that, that, and that. Then divide by
> something, and
> something else. … hmmm…. a few bits just went missing. Could you reorder
> and fiddle to fix some of this? Sure, that’s where we get back to the
> range stuff.
> Even if it’s not in the “main loop”, GPSDO code is full of checks for this
> or that.
> Like the main math, they are scaled and tested for the normal range of
> Not all of them spurt error messages when they get involved. Some just
> bump this
> or that and move on.
> Lots of possibilities ….
> > Try setting up for say a 10,000 second time constant and see how things
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