[time-nuts] Anyone want an engineering job making a GPSDO comparator for T-Bolts?

[Charles Steinmetz]

Chris wrote:

>I wonder what you gain by this?  You still need the GPS to provide a
>reference.  Either you use its 1Hz or 10MHz output.   Then you compare the
>phase of these to the phase o the TCXO and adjust the TCXO until the phase
>is constant relative to the reference.

Certainly if you start with a GPS that puts out 10 MHz (i.e., a 
GPSDO), there is very little reason to use the 10 MHz to lock the 
internal TCXO rather than simply replacing the TCXO output with the 
output of the GPSDO (plus whatever dividers, etc. are necessary if 
the TCXO frequency is not 10 MHz, which are already part of the 
current solution as I understand it).

The real reason to make the change would be to replace the pricey 10 
MHz GPSDO with a $2.00 GPS module that puts out only a PPS 
signal.  Of course, the PLL is much more complex when you are locking 
to a PPS signal, so the cost of the newly-designed PLL would bridge 
some of the price gap.

Best regards,

Charles