A recent query about the calibration process for the KTCX03-1 1 ppm TCXO option prompted me to compare my TCXO data sheet with the (yet to be implemented) Reference Oscillator Method 3 procedure in the Owner's Manual. It became apparent that the procedure in the Manual does not support the data that accompanied my TCXO.
I received a table of frequency deltas at 5-degree Celsius intervals of temperature. Abridged for possible operating temperatures, it is: Temp Ppm 5 -.17 10 -.03 15 .01 20 .05 25 0.00 30 .29 35 .56 40 .60 45 .71 Obviously, interpolation is necessary. Piecewise-linear interpolation (linear between the two nearest tabular points) would seem appropriate, particularly because other procedures might result in interpolated values outside the range of those in the table, due to unexpected data points like the local minimum at 25 degrees in my table. (I'm still wondering about that local minimum.) After interpolation, the oscillator frequency could be adjusted by multiplying by ( 1 - Ppm/1000000 ) to compensate for drift. This could be implemented by multiplying the displayed value set by Method 1 or 2 for CONFIG:REF CAL from the (unchanged) displayed value to a corrected value for use in later K3 calculations. With this approach, a default table of zeroes at all temperatures would continue to work for those not having the TCXO option. The Reference Oscillator calibration procedure would consist of (a) Input the ppm table for the optional TCXO, if you have one. Be sure to input signs and decimals. (b) Set CONFIG:REF CAL by Method 1 or Method 2, as preferred. (CONFIG:REF CAL would set the displayed value *before* adjustment by the factor in the previous paragraph, so that temperature changes would not change the displayed value.) With this procedure, it shouldn't be necessary to do step (b) at any particular temperature. 73, Paul W8TM _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
