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Question asked by pepe.federico Employee on Sep 18, 2015
Hello Maurizio,
first of all the answers:
1) The way we can measure it can be getting:
- a TX node with a TX signal output on GPIO 
- a RX node with a SYNC detected signal output on GPIO
- a scope
The time delay can be measured as the event when the last bit of sync is put on the air and the SYNC detected signal is asserted (propagation time of these signals in the silicon is almost negligible). 
Time between them is 13 bits time about.

2) No. For sure the device must be in RX state

3) Yes, it depends on the first word that matches one of the possible patterns admitted contemplating errors. So it is definitely not predictable.

4) It is 13bits time. 

Anyway, we are talking about signals propagating at the speed of light (this means that we'd have ~3us for 1 km!).
Even if You have an extremely fine timing measurement Your measure could be disturbed by ray scattering or by the jitter on the XTAL used to supply the RF (that is the clock reference for all) .