[time-nuts] Re: GPSDO/GNSSDO project: STM32G4 + u-blox ZED-F9T + TDC7200

[Carsten Andrich]

Hi Bob,

On 06.08.22 18:50, Bob kb8tq via time-nuts wrote:
> As many have found, dealing with OCXO’s in changing environments is a bit
> exciting. They most certainly do go in a variety of settings. Something around
> 99% live in a fixed / bench sort of install. The spec sheet data on a catalog part
> is inevitably talking about a very stable situation. Performance is always degraded
> if things like shock / vibration / acceleration / temperature change are involved.

For my prototype I just picked a readily available, not too expensive 
OCXO. If the prototype works out, of course an OCXO with low 
g-sensitivity is due for the next iteration. Specialized 10/100 MHz 
OCXOs with <0.2 ppb/g sensitivity on the worst axis are available, but 
not exactly cheap.

> Without a target accuracy spec on the device, there really is no way to know if
> this or that approach is going to work. Is this a time source? Is it just a frequency
> reference? What is the target accuracy in the real world?  What is the “vehicle”
> and what are its characteristics
I require time (and therefore implied frequency) synchronization with 
<10 ns accuracy. 1 ns would be preferred, as I already reached that for 
stationary applications with SRS FS740s. My use case is coherent 
sampling for spatially distributed software-defined radios and 
millimeter wave frequency converters. The vehicle is primarily a car, 
but may also be airborne.

> and we never even made it
> to the problematic filter on the DAC
Could you elaborate on that, please?

Thanks and best regards,
Carsten