Neil Baylis wrote:

>> I looked at many ways to try and get a wide area, very accurate timing
>> signal for an amateur radio astronomy project, and a GPS disciplined ultra
>> stable frequency standard was about the only way to go. $$$ <--
> 
> 
> You can buy a GPS timing receiver that will give you a local 1Hz reference
> that's within 20ns of UTC for less that $100. Check out the Trimble
> Resolution-T for example. It would be hard to do better than this for the
> money.

True. And for most time of day applications, that's good enough.
To do VLB interferometry @ 1420 MHz, one needs better than 100ps accuracy.
To do gamma ray burster direction finding 1 ns is OK for amateur
level work.
Ideally, the various sites would have a 10 MHz reference which was
absolutely in sync (<100ps) to use as reference for time stamping
the samples, and GPS time to get gross phasing of the data.

Robert
If you have only two clocks, with different values, what time is it
really?

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