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
---
http://www.elecraft.com
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