[time-nuts] Alternate frequency sources - second opinions

[Magnus Danielson]

J. Forster wrote:
>> Somebody mentioned TV and radio stations recently.  (I think it was part
>> of the North discussion.)
>>
>> What sort of frequency source is at the root of the local TV or radio
>> stations?
>>
>> Is the sync timing for TV stations derived from the same source as the
>> carrier?  Or are there two separate clocks to discuss?  How about the
>> color-burst frequency?
> 
> NTSC is gone w/ analog TV. No color burst any more.

There are other forms of pilot-signals in the OFDM spectrum. That is 
needed to keep the digital receiver frequency locked to the signal. Read 
the specs of your favorite terrestrial digital network of choice.

>> What do radio/TV stations do for backups?  If there was a hurricane or
>> earthquake that broke the main transmitter are they likely to switch to a
>> backup with a different timing source?
> 
> I'm not sure, but when satellite links go down, the picture freezes. That
> implies a frame store which is likely bad news for timing.

That is what the MPEG-2/4 decode does. It stops updating it's play-out 
frame-buffer. It's not a frame-store by necessity.

Cheers,
Magnus