[ARC5] SCR-274 calibration Xtals

[Bruce Long]

Looks like your crystal drifted upwards .570 ppm in 70 some years giving a long term aging specification of about 8 ppb per year.

But wait not all of that drift is from the crystal.  A capacitor or two or three in the oscillator circuit could have drifted, the initial set tolerance was likely not much better than a few ppm and the temperature stability as well as operating voltage has an effect as well. Resistor value changes might well have a significant effect at this level of precision.
Having worked in the crystal and crystal oscillator business for many years I think this level of stability for a non precision, mass production grade 70 year old crystal is absolutely superb.
I wonder how good the $.79 quantity (1) AT-strip resonator  13 MHz crystal I am desigining into my current design project at work will be in 70 years.


      From: "k1uhy at comcast.net" <k1uhy at comcast.net>
 To: J Mcvey <ac2eu at yahoo.com> 
Cc: arc5 at mailman.qth.net
 Sent: Thursday, August 18, 2016 7:28 PM
 Subject: Re: [ARC5] SCR-274 calibration Xtals
   
I wouldnt bank on an almost 80 year old rock being forever accurate or even dead on from new. What was the original tolerance spec?
From: "J Mcvey via ARC5" <arc5 at mailman.qth.net>
To: arc5 at mailman.qth.net
Sent: Thursday, August 18, 2016 10:57:08 AM
Subject: [ARC5] SCR-274 calibration Xtals

Just for fun, I decided to see how the magic eye transmitter calibration system worked in practice.It actually worked pretty well, but the resonance  was at 3502 khz instead of 3500 khz ( marked on xtal) . Is this typical?BTW, does anyone have the 8000 khz xtal( I think that's what it's supposed to be) for the BC-459 to sell?
JIm


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