[time-nuts] Brand new OCXO/TCXO reccomenations

[jimlux]

On 9/25/20 5:50 PM, Mark Goldberg wrote:
> Those look pretty good compared to some I got. See attached.
> 
> I'm purchasing a small, custom frequency run and it is cheaper for me to
> super select than for the manufacturer to do so. In fact, they won't set up
> that kind of testing for such a low volume. I'm lucky to get them at all.
> About 70-80% looked like your examples, but there were a number of
> outliers. I would expect that if you buy a common frequency they would have
> the process optimized.

interesting.. those were for 49.244792 MHz, which is hardly a standard 
frequency. But they were for a space application..

> 
> Regards,
> 
> Mark
> W7MLG
> 
> On Fri, Sep 25, 2020, 11:51 AM jimlux <jimlux at earthlink.net> wrote:
> 
>> On 9/25/20 8:55 AM, Mark Goldberg wrote:
>>> Note that many (maybe all) TCXOs exhibit a hysteresis effect when the
>>> temperature cycles. The stability reported on the datasheets is only
>>> tested with a temperature change in one direction. Cycling temperature
>>> up and down will result in more variation.  I've seen two or three
>>> times the datasheet variation when cycling some TCXOs between 0 and 50
>>> C and have had to super select for this. I've also seen non monotonic
>>> jumps. Aging is also very significant in the first few months after
>>> soldering.
>>>
>>
>> I've attached a couple plots showing the hysteresis of two different
>> TCXOs (fairly good ones) - so you can get an idea of the amount of
>> variation.
>>
>> 10 ppm easy, 1 ppm hard.
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