[Elecraft] Re: K3 Reference Oscillator

[wayne burdick]

On Aug 29, 2007, at 10:16 AM, Mike S wrote:

> 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*.
>>
>> +/- 0.5 ppm (or +/- 1 PPM) is the most common high-stability 
>> reference option available for ham transceivers, K3 included. (And 
>> yes, this applies to the entire temperature range, not per degree C.)
>>
>> The K3 has an advantage over most transceivers in this regard. 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. So we're 
>> actually expecting something like +/- 0.2 ppm over temperature. But 
>> we're specifying it conservatively.
>
> I assume then that the high-stability option can also be calibrated to 
> achieve 1 Hz through 6 meters at the calibration temperature, too 
> (that was not stated)?

You can achieve 1-Hz accuracy at the calibration temperature with 
either the standard or high-stability TCXO.

The REF CAL menu entry can also be used to enter Freq-vs.-Temp data 
with either one, but this data is only provided for the high-stability 
unit. One could enter data for the standard oscillator, too, but you'd 
have to determine what data to enter by manually calibrating to a 
reference signal at each temperature point (5 degree increments). So 
you could set the high-temp CAL points on hot days and the low-temp CAL 
points on cold days. I'm not sure what overall temperature stability 
you could achieve using this method with the standard unit, but we'll 
be trying it at some point. Meanwhile, if you really want the best 
stability over temperature, I'd recommend the high-stability unit plus 
entering the data as supplied.


>
> Can the standard reference use a calibration table, so it might become 
> more accurate as it is hand calibrated at different temperatures?

Exactly -- see above. The manual will describe how to do this.


73,
Wayne
N6KR


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