[time-nuts] Using digital broadcast TV for timing?

[Jim Lux]

On 2/7/12 6:01 PM, Chris Albertson wrote:
> GPS requires a good view of the sky,  Hard to do in say the 7th floor
> of a 40 story building if you have no windows.   I'm wondering about
> using the new digital TV signals for timing.
>
> I'm pretty sure there is time code in the signal and I'm pretty sure
> the bits are clocked at a very accurate rate.   Also TV receivers are
> very easy to find and put "hooks" into.      I'd bet the broadcast TV
> signal could be almost as good as GPS.

Actually, no... because it's so easy to do frame buffering/time base 
correcting to fix anything.

Back in the bad old days of analog everything, you needed really good 
sync and timing to make things like switchers and faders work. A time 
base corrector was wretchedly expensive, so you'd go to a lot of work 
distributing black burst around and syncing your tape machines, etc.


>
> The plan is to try and phase lock a local oscillator and use a very
> long time constant on the loop filter.   I bet the TV transmitters are
> locked to GPS and over a long enough time are as good as GPS.  Also in
> many cities there are many TV transmitters, should be able to take
> advantage of that.
>
>   Before I try some experiments anyone want to tell me why I'm wrong?