> Define cheap. > You can already get essentially single chip TICs with a resolution (and > accuracy) better than 100ps for around 100 Euros or so.
Has anyone in the group tried one of these? I would very much like to see the results. > However sawtooth correction is cheaper than using a hardware variable > delay line. Good point. > However the optimal solution doesn't use a TIC at all, just use a good > GPS receiver that makes the carrier phase observables available. > Quite a few of the older receivers used to make the carrier phase data > available. Many of the Oncore VP's did this, but I don't know of anyone, amateur or commercial, that built a GPSDO using that feature. That makes me wonder if carrier phase observables alone is not enough. > The catch is that the GPS receiver local oscillator must be phase locked > to the OCXO. > Some receivers use a 10MHz crystal oscillator in which case this can be > removed and replaced with an external 10MHz signal derived from the OCXO > being disciplined. Right, this is the key. Do you know any OEM receivers that allow an external 5/10/20 MHz? I know my Z12T does (but that is far from an OEM receiver). > Unfortunately there are as yet no relatively inexpensive off the shelf > implementations of the GPS carrier phase discipling technique available. > The calculations involved for maximum performance are somewhat complex, > however not too much computing horsepower should be required. The QL carrier phase GPSDO is unique and probably not cost-effective. Sounds like it's a custom single-channel GPS receiver designed from the ground up. If there were an easier way surely someone would have done it in the past ten years. > Magnus hopes to remedy this lack of suitable software and hardware > sometime in the future. That would be very nice. Will it be L1 only or L1/L2? /tvb _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
