[time-nuts] Precise Time transfer and relative position over a short baseline

[jimlux]

On 4/11/16 1:40 AM, Björn wrote:
> Hi Bruce,
>
> For such short baselines single frequency GNSS should be able to keep fixed integer solutions. Not sure how much money thas is going to save, since you might need timing specific geodetic receivers to get external 10MHz input.
>
> Did you consider implementing time transfer using time reversal using say a sdr tranciever (usrp or other) where your clock is driving the radio. As done on HF by Yen & Sengupta at last PTTI.
>
> https://www.ion.org/ptti/abstracts.cfm?paperID=3373
>


VLA used VHF (I think) radio links to provide common phase reference 
among apertures.

Consider, for example, using a 1 GHz CW carrier among your stations. 
With good SNR, tracking phase to 1/1000th of a cycle should be 
straightforward.

The challenge will be (as always with this kind of thing) the mechanical 
effects.  Motion of 1mm is 3ps.

On the other hand, my victim detection radar trivially measures 1mm 
displacements in path length with 20 dB SNR with EIRP of 1 mW, omni 
antennas, and a range of 30m with a 0.1 square meter target.  That's at 
3 GHz.