On 09/04/2024 21:48, John Ackermann N8UR via USRP-users wrote:
I'm not sure about this particular unit, but typically if a crystal
oscillator datasheet lists an "accuracy" specification, that is over a
time period that takes into account the long-term frequency drift
("aging") that affects almost all oscillators. Sometimes the accuracy
is specified over a period of years, especially if the oscillator
doesn't have a frequency adjustment input. In oscillators that can be
tweaked, it might be stated as an aging rate of some value per day,
week, or month.
In inexpensive oscillators, the "stability" number usually refers to
short-term change due to temperature and other environmental factors.
In more expensive oscillators, stability is usually specified over
various averaging intervals, say from 1 second to 10K seconds.
Sometimes accuracy is also expressed as a combination of time and
temperature range, which gives the most conservative result.
John
----
See also Allen Deviation plots....
On 4/9/24 21:19, Timothy J. Salo via USRP-users wrote:
Hi,
I'm writing a "Getting Started" guide for our research group. When I
got to the GPSDO section, I had difficulty in figuring out the frequency
stability and the frequency accuracy of the B210.
At least the early versions of the B210 used a CTS Electronic Components
520L20DA40M0000 TCXO. The datasheet for this TCXO says it has a
frequency _stability_ of +/- 2.0 ppm over an operating temperature range
of -30C - +85C.
The CTS website states that their TCXO exhibit: "Stratum 3 Performance;
±4.6ppm overall, ±0.28ppm over -40°C to +85°C". Am I correct in
concluding that this is the frequency _accuracy_ of the TCXO used in
the B210? Does this translate directly into the frequency _accuracy_
of the B210?
The B210 datasheet states a frequency _accuracy_ of +/- 2.0 ppm. Is
is a typo, and should the datasheet actually say frequency _stability_?
Or, did someone conclude that over a reasonable operating temperature,
the effects of temperature outweigh any inaccuracy in the frequency
of the TCXO?
Anecdotally, I have heard that one organization found that three of
their four B210s, when operating as a 5G base station, were unable
to connect with commercial off-the-shelf cellular handsets, unless
an external GPSDO was used with the B210. Does anyone have any idea
what frequency accuracy is expected by cellular handsets?
So, does anyone know what the frequency _accuracy_ of the B210 is, in
the absence of a GPSDO? Or, should I just use the +/1 2.0 ppm figure?
Thanks,
-tjs
- - - -
[1]
https://www.ctscorp.com/Files/DataSheets/Passives/FCP/TCXO/TCXO-520-datasheet.pdf
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