[time-nuts] Re: pulling some crystals

[Bob kb8tq]

Hi

Their idea that 3 days at 105 is the same as 1 year is …. errrr …. ummm ….. questionable. Even more so in an oven application that will have the crystal running at something well above room temperature (our starting point for the thread was heating it to 60C ….). 

Simple example: 

A typical OCXO crystal can easily be 20C above the max temp spec on the device. If the OCXO is rated to go to 70C, that would be 90. In the case of 85C, you are up at 105C. If indeed 3 days is a year, those 85C OCXO’s would have an insane daily aging rate. In practice, that’s not what folks observe.

Bob

> On Dec 7, 2023, at 3:07 PM, glen english LIST via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> thanks Bob and Rick for your fine input, Rick thanks for the treatment , I will follow your recipe and report back. Yes these days I have troubles with AVAILABLE SMT RF transistors, they all have Fts 4-10 GHz and I generally resort to common base with ballast R. 2N5179 I used to put a bead on the emitter lead as described in "ARRL Solid State Design " remember that ?
> 
> If I ran out of pull after 10 years  while  I can tell the radio just to go off freq a bit (digital fix in FPGA) , the issue then is the digital sample rate fixed to the oscillator  go off meaning the world runs fast or slow.
> 
> From the manufacturer, Krystaly ,  on my batch of 3OT  98.304 crystals : I reproduce word for word here. These guys are very helpful.
> 
> "
> 
> All our crystals have undergo the process of preaging, also called "accelerated aging" (i.e. 3 days storage at +105 deg.C). This aging is equivalent to one year aging at normal temperature (according standard IEC 60122-1). The crystals produced for you had frequency shift after this preaging below 1.0 ppm, so it guaranties aging below 10 ppm after 10 years. The aging curve shows deceleration (saturation) in time.
> Information to pulling parameter:
> Trimsensitivity at frequency 98.304 MHz, 3.rd  overtone is approx. 35 ppm/pF.
> Trimsensitivity at frequency 32.768 MHz, 1.st  overtone is approx. 400 ppm/pF so ten times higher."
> 
> regards
> 
> On 8/12/2023 4:19 am, Richard Karlquist wrote:
>> 
>> When I was working for Zeta Labs, circa 1978, I was in charge of a huge order for 5th overtone VCXO's.  My boss told me to use the "standard Zeta VCXO design".  It had various problems, and I quickly decided to invent a new design that actually worked right, and quietly put it into production without alerting my boss.  The new design was wildly suc
>> 
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