[time-nuts] Advantages of GNSS ???

[Mark Goldberg]

That is the dirty little secret of crystals. Manufacturers will test the
temperature response in one direction, but if you heat and then cool
crystals and measure the frequency, they do exhibit significant hysteresis.
I've not been able to get a supplier of TCXOs for me to characterize this
as I don't buy enough. I just have to test them myself and toss the 10% or
so that don't meet their specs due to the hysteresis. If you cycle the
temperature up and down multiple times, the effect lessens, but after
letting them sit for a while, it comes back. I also saw jumps at particular
temperatures, but that may be due to the TCXO compensation.

Mark


On Tue, Jul 9, 2019 at 4:00 PM Glen English VK1XX <
glenlist at pacificmedia.com.au> wrote:

> and non monitonicity in the device is the death of a control loops.
>
> My attempts at building good OCXOs using cheap AT crystals in the 90s
> was thwarted by.... non monotonic bending crystals !
>
> And everytime they would wake up, the monitonicity would be in a
> different part of the control curve....
>
> and they exhibited hysteresis, like defined steps , this seems to be the
> case with most crystals, the harder you looked, the more undesirable
> imperfections you found...
>
>
>
> On 10/07/2019 5:57 AM, David G. McGaw wrote:
> > Leo -
> >
> > I do believe you mean non-monotonic, rather than non-monotonous. Not
> > being monotonous is a good thing.  :-)
> >
> > David N1HAC
> >
> > On 7/9/19 1:20 PM, Leo Bodnar wrote:
> >> It's not very good, it is highly non-linear and even wor
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>