[Elecraft] 10 MHz external reference - GPSDO

[Don Wilhelm]

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?