richard at karlquist.com
Tue Oct 2 15:20:06 EDT 2007
This question keeps coming up in relation to various crystal
oscillators. Basically, if you have a really good process,
which HP had for the E1938A, there will be no bias in favor
of aging in any particular direction. If there was any
bias, the cause of it would be investigated and then eliminated.
The main source of aging that remains is believed to be microcracks.
These can increase or decrease frequency.
Now if you are talking about colorburst crystals, they usually age down
because crud from the package deposits on the crystal to
a greater extent than dirt on the crystal flying away.
Brooke Clarke wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+richard=karlquist.com at febo.com RETRY
> Hi Rick:
> If the aging drift is up in frequency then there might be an advantage in
> starting at the low end of the window. Any idea of how these age?
> Have Fun,
> Brooke Clarke
> http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
> Richard (Rick) Karlquist wrote:
>> ); SAEximRunCond expanded to false
>> Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
>> The labels may or may not be significant. If the frequency
>> is indeed -2.94 Hz at 2.5V EFC, you could probably get it back
>> to 10 MHz by increasing the EFC voltage. You can also decrease
>> the bridge capacitor to bring the frequency up if necessary.
>> The factory was supposed to choose the capacitor to get 10 MHz
>> in the center of the EFC range. If this is not correct, the
>> oscillator is usually perfectly OK , and they just
>> goofed on the capacitor. The capacitor installation process
>> had a lot of problems. Should be safe to power it up and see
>> what the status is.
>> Rick N6RK
>> Jeroen Bastemeijer wrote:
>>>); SAEximRunCond expanded to false
>>>Errors-To: time-nuts-bounces+richard=karlquist.com at febo.com RETRY
>>>After some shipping time, my E1938 arrived today! :-) :-) :-)
>>>Thank you Rick!
>>>First thing was examining the board, oscillator and the HP-test
>>>notes/labels. Most of the specs mentioned there are logical and numbers
>>>are very reasonable. ;-) However, one spec drew my attention: "Hz off
>>>freq. after warm up: -2,94". Does anyone know what it means? Is this the
>>>offset after warm-up without EFC applied?
>>>The unit hasn't been powered up. Whit the hardware at hand I first want
>>>to read some docs to be sure about what I'm doing. For comparison, what
>>>other numbers are around for the "Hz off freq. after warm up"-spec?
>>>Final result of the HP-test was: PASS. So, I assume this number is OK.
>>>What is your opinion? Looking forward to your reactions.
>>>73 Jeroen PE1RGE
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