Mike, the counter resolution was 40ps with am RMS resolution of 120ps
Erik.
On 18-2-2022 11:36, Mike Ingle wrote:
Hi Erik.
What is your counter resolution/gate time? At 1second, the interval
difference from 10MHz + 5mHz is 500ps. --mike
On Fri, Feb 18, 2022 at 11:20 AM Erik Kaashoek <[email protected]> wrote:
During long term testing of some 10 MHz TCXO the output frequency seems
to jump within one second 20 mHz ( millihertz) up in frequency every
110 seconds up and after a 25 seconds, again within one second, the same
amount down. The noise in the frequency measurement was well below 5 mHz
In an ASCII drawing of frequency versus time this looked like:
________|~~~~|___________|~~~~|________
Sometimes the high frequency period was very short (some seconds) or
absent but the overall period was within 5 seconds constant
This was tested with 4 different power supplies, although all where
mains connected, not yet tested with battery only, 2 different counters
and two different reference frequency standards.
The TCXO was thermally shielded and testing with some cold air showed a
different behavior for external temperature changes (fast jump away and
slow return to stable frequency)
Also, with thermal shielding removed, touching the TCXO showed also a
fast jump away and slow returning to stable
Measuring the supply voltage did not show clear changes but the used
voltmeter only had 4 digits resolution.
The official spec of the TCXO is much worse so the device is well within
spec but I'm trying to understand why this could happen.
Does anyone know a possible cause for this behavior?
Could this be a small mains supply variation in a 110 seconds long cycle?
Or what else?
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