[time-nuts] Advantages of GNSS ???

[Bob kb8tq]

Hi

TCXO’s are very different beasts than OCXO’s. In an OCXO, the crystal is not exposed
to any significant temperature change. 

Bob

> On Jul 9, 2019, at 8:05 PM, Mark Goldberg <marklgoldberg at gmail.com> wrote:
> 
> 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
>> 
>> 
>> 
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