I am hearing that you have an external reference that takes some time to
warm up after you turn it on, and that causes the K3 to move frequency
with the warmup drift of the external reference.
If the external reference is stable when the K3 is turned on, there is
no need for the K3 to ignore the external reference.
If the K3 were to ignore the external reference for 15 to 20 minutes
after the K3 is turned on, then it would have to do the same thing after
every power cycle. If I were using an external reference, I would not
want the K3 to do that. If I use an external reference, I would want
that reference to be accurate at all times, I think the best answer is
to power the reference continuously.
As a parallel, the high stability 10 MHz reference oscillator in my
universal counter is powered whenever the counter is plugged in - when I
use the front panel switch to turn the counter on, I can trust its
accuracy without waiting for it to warm up. If I used an external
reference with the K3, I would want the same results.
73,
Don W3FPR
On 10/16/2014 8:39 AM, Brian wrote:
Don,
The issue isn't whether the TCXO is an improvement over the standard.
The issue is whether the TCXO is good enough for some of the wide
range of uses the K3 is put.
What you are hearing here is that it isn't. Elecraft has responded
with the external locking option. That option, being a discontinuous
correction, one has some significant disadvantages to some.
My original posting on this issue was related to the locking option.
It only seemed reasonable to have it do a sanity check on the
difference between the internal and reference oscillator implied
correction before doing a correction. Why do the correction is the
external oscillator is warming up and 250 Hz off initially? The K3
also drifts during warmup with both the standard and TCXO. This
amounts to between 20 and 50 Hz (@ 10 MHz) for the first 15 minutes.
Why do the correction until the K3 has is relatively stable. Perhaps
the external locking should not be done for say the first 15 minutes
after K3 turn on?
73 de Brian/K3KO
On 10/16/2014 12:06, Don Wilhelm wrote:
Brian,
The High Stability TCXO (1 ppm) is not a separate Elecraft product - it
is an option for the K3 offering better specs than the stock TCXO (5ppm)
- yes, both are a TCXO.
The temperature stability was found to be far better than the 1ppm
specification without the temperature compensation routine, so
implementation of that K3 routine was dropped from the plan (and also
from the manual).
73,
Don W3FPR
On 10/16/2014 7:39 AM, Brian wrote:
Ken,
There is an Elecraft product called the TCXO. It is capable of
temperature stabilization BUT Elecraft has not implemented that
function.
Perhaps though should be given to implementing the temperature
compensation capability. My understanding is that there is some
difficulty in doing that and maintaining low phase noise.
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