[time-nuts] GPS discipline oscillator vs phase lock
kb8tq at n1k.org
Fri Jun 16 21:15:31 EDT 2017
> On Jun 16, 2017, at 7:24 PM, life speed <life_speed at yahoo.com> wrote:
> That sounds like phase-locking the oscillators to a local radio transmitter. Not sure there is any difference post-processing vs. real time.
The advantage is that you capture a much wider bandwidth signal than you can lock to. That lets you extract better “instantaneous phase” information. With the narrow band loop normally used for locking, loop dynamics get into the picture. That on top of the RF propagation issues is a bit of a mess. It also is quite possible to capture multiple radio (or TV or …) transmissions and post process against all of them.
The bottom line is still that “many degrees” at 100 MHz is far more practical than “tenth of a degree”. There are very few options if your application really does need roughly a tenth of a degree.
> - Lifespeed
> A far more common approach is to let the two oscillators free run and to record something like a local broadcast station.
> You then post process all of the data to give you the phase accuracy. One of several gotcha’s is the stability of any
> radio link at the level you are looking for.
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