[Elecraft] Re: K3 Reference Oscillator

[Mike S]

At 12:48 PM 8/29/2007, wayne burdick wrote...
>Maybe I wasn't clear on this. I said it was "accurate to 1 Hz ... at 
>the calibration temperature." That says nothing about what happens as 
>the temperature *changes*.
>
>[high stability] +/- 0.5 ppm ... applies to the entire temperature 
>range, not per degree C.
>
>The REF CAL menu entry can be used to enter frequency-vs.-temp data 
>that's supplied with each individual 1 PPM oscillator. This data is 
>used in conjunction with an accurate temperature sensor to fine-tune 
>the reference in 0.2-Hz steps as the temperature changes.

Can the high stability reference also be calibrated at temperature to 
achieve 1 Hz, like the standard reference, or must one trust the 
calibration table which provides 0.2-0.5 ppm (10-25 Hz) accuracy? If 
calibrated at temperature, does the delta then offset other table 
entries (which might be used to accommodate crystal aging, for 
example), or are individual table entries calibrated? Can a calibration 
table be used with the standard reference?

I can see some applications where "1 Hz, but you have to calibrate if 
the temp changes" is better than "10-25 Hz, but you never touch it."