[Elecraft] KTCX03 Questions and experience

[Brian Alsop]

Guys,

Put this in the K3.  Some questions. Would appreciate some enlightenment 
from the experts out there.

It has only three pins which I suppose are +V, ground and signal out.

What does changing REF CAL do since there is no "adjustment" pin?

Also I expected to only have to tweak a well calibrated K3's REF CAL a 
small bit after installing the TCXO.  Not!  REF CAL had to change by 536 
to zero beat WWV on 10 MHz.  Not found any goofy settings that would 
explain that.

Have no way of knowing the internal unit XTAL temp.  So I looked at the 
front panel temp vs frequency change for the first hour of warm up. 
There seems to be little temperature compensation between 19 and 30C 
while there is measurable drift.  Alternatively the compensation 
routines do as good as they can (and much better than the uncompensated 
stock oscillator) over this range.  Compensation appears good after 30C 
up to the 35-36C temps reached after 8 hours. This may be a meaningless 
observation.  Perhaps the internal KTCX03 electronics temps have 
stabilized by then.

Another perhaps meaningless observation.  Again using the front panel 
temp as an indicator.  The unit exhibits a positive temperature 
coefficient for the first hour and then becomes negative.  The stock 
oscillator has a negative coefficient.

It appears to work as advertised.  For normal use temperature 
transients, it easily makes the +/- 0.5 ppm spec -- overkill for most 
everybody.  I have some 8 hour long plots of this and the standard 
oscillator warmup drift if anybody is interested in the nits.

A literature search on TXCO compensation methods uncovers something 
interesting.  A neural network approach gets the drift down to 0.005 
ppm.  It learns how to compensate as it goes.

I wish REF CAL had one more significant digit.  The last REF CAL digit 
amounts to 0.5 Hz per REF CAL unit at 10 MHz.

The K3 is more than a rig, in many areas it approaches a lab instrument.
I use it as such often.

What are your experiences?

73 de Brian/K3KO


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