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 <jim...@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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