[time-nuts] Accuracy of GNSS Frequency Standards on different satellite systems

[martyn at ptsyst.com]

Hello,

 

We manufacture GNSS Frequency Standards, both Rubidium based and OXCO based.

 

When comparing the frequency and phase outputs of two GNSS Rubidium
Disciplined units, that are connected to the same antenna and receiving the
same satellite systems, we get very low frequency difference and phase
change over seconds to weeks.

 

My customers asked me how good two of our units will be when placed about 1
km apart.

 

They need two units to remain in phase are two different locations, as I
said about 1 km apart.

 

The customer wants to know how the phase stability of the sinewave outputs
will suffer or degrade, when receiving slightly different satellites with
two separate antennas.

 

Our units can pick up GPS, Galileo, Beidou and Glonass.  We usually have
them receiving GPS and Galileo and Beidou and not GLONASS.

 

I'm trying to simulate a worst-case scenario by having one unit receive GPS
only and the other Galileo only, while still using a common antenna.

 

Does anyone have an idea how the performance may degrade at 1 km apart but
both units receiving GPS+Galileo+Beidou?

 

It will take many weeks of testing for me to draw conclusions, so I'm hoping
someone already have done this experiment.

 

Best Regards

 

Martyn Smith