[time-nuts] Time Signals on TV signals

[Lux, James P]

On 5/25/09 9:52 AM, "Bill Hawkins" <bill at iaxs.net> wrote:

> Aficionados of accurate time,
> 
> I have two Panasonic DVD TV recorders, a DMR-EZ27 and 28. They were set to
> automatically sync time to a TV station. This worked fine until a few months
> ago. Now they are on manual time, but, of course, they drift.
> 
> Tried to turn automatic time setting back on this morning. The screen says,
> "This may take a few minutes." It still said that 10 minutes later, as the
> busy indicator continued to rotate through three spots.
> 
> Gave up on automatic and asked the only group I know that might know.
> 
> Why did TV stations stop broadcasting time signals? HDTV requirements?

How does the time get transmitted?  On the Vertical Interval?  Which doesn't
exist on HDTV, but I would imagine there's an equivalent sort of time code
on the digital data stream (if only to allow multiple streams to be sync'd)




> 
> Could a cable company interfere with the time signals?

You betcha... There's no requirement on them to carry anything in any
particular way. Transcoding, remodulation, resampling, not to mention that
the basic transport layer from the headend to the user is not necessarily
time synchronous..  Heck, they have trouble carrying emergency traffic
properly, and they DO have requirements for that.

And over the air signal is your best bet.


Jim