[time-nuts] TV sync

Jeffrey Pawlan jpawlan at pawlan.com
Sun Oct 7 12:03:45 EDT 2007

> Hi Tom,
> a related very interesting experiment is to take the Horizontal Sync signal
> from an old Tube-type TV, and feed it to a frequency counter with GPSDO time
> base (preferrably).
> Got to be careful about the high voltages inside the TV though!
> BTW: it's not 15374KHz, there are some significant decimal digits (I don't
> recall the formula to calculate the frequency exactly, but it was the total
> number of frame lines multiplied by 59.94Hz or so).
> Then you can test how accurate the broadcasters' 27MHz reference clock  is.
> One would be surprised how inaccurate(!) some broadcasters are, and how  much
> drift some Satellite providers have.
> A lot of the stability is dependent on the receiver of course, and how well
> the receiver's VCXO locks to the Broadcaster.
> bye,
> Said


All larger TV stations use Cs standards. What you don't know is that the FCC
assigns SLIGHTLY different scan frequencies to each station on the same
channel in a close area so when you are in a fringe area between two stations on
the same channel, you will intentionally see both pictures superimposed with a
rolling of the scan lines. Otherwise they would be locked and you would see
only black and white bars.

Satellite broadcasts are completely different and I do not know the FCC
specification for those.

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