I think everyone is ignoring something here. What causes the frequency
drift in the first place?
It is temperature changes - the designation TCXO signifies Temperature
Compensated Xtal Oscillator. It is already compensated for temperature.
If the temperature of the TCXO stays the same, the frequency should be
stable.
There will be some frequency change during warmup after power on, and
there will be some frequency change during transmit because the
temperature inside the box will increase, and will cool during periods
of receive.
The difference between the TCXO-1 and the TCXO-3 is one of how much.
The TCXO-3 drift will be smaller than the TCXO-1 over the same
temperature change.
The drift over the 4 or 5 second correction from the external reference
will result in a small correction with either TCXO, but it will be
smaller with the TCXO-3.
Additionally, the frequency drift will be quite small even without the
external reference unless there is a rapid and drastic change in
temperature at the case of the TCXO. These discussions should include
the temperature change during the measurement periods. to complete the
picture.
73,
Don W3FPR
On 3/13/2016 5:27 AM, Oliver Dröse wrote:
Thanks Ed.
I don't have a problem understanding how the TCXO's work. Maybe I was
not clear enough. ;-) Taking your example from below, having only the
TCXO-1 it is surely *not* drifting 140 Hz at 28 MHz within the 4 or 5
seconds of the EXREF update cycle (same as the TCXO-3 will not drift
by 28 Hz in that time), otherwise the K3 would be a *very* crappy
radio. ;-) Think you are missing the time domain here. ;-)
So my question still stands: What's the real value of the TCXO-3 over
the TCXO-1 when using the K3EXREF?
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