[time-nuts] TV Signals as a frequency reference

[w4wj at aol.com]

Dana...
 
Back in the day when out of studio news stories were
shot on film, which was then processed at the studio 
and broadcast from a "film chain" stations would lock 
their sync generators to the incoming network signal
during network hours.  That allowed "clean" switching 
in and out of network programming.
 
When you were in the local programming portion of the 
day, the local sync generator would not be "looking" at 
the network signal for reference.  That was done because 
there may have been times when the AT&T microwave 
network was down for maintenance.  Obviously this was 
before the days of satellite delivery of the network services.
 
You are correct...  when the "Live Truck" came on the
scene with instant on scene video, etc, the demand
for frame syncs at each station went up.
 
Our first frame sync at, WTVJ in Miami, had been used
at the Cape for some of the moon shots.  It was a huge
box, occupying about two feet of rack space!
 
Later frame syncs, would drop in size to 1RU!
 
All those frame syncs were locked to our local
master sync generator.  At one of our monitoring
positions I could compare our local 3.58MHz
color burst frequency to the networks and adjust
the phase so they were in agreement.  This was
just a good method of checking our "in house"
reference to have it on frequency.  If the 3.58
was on frequency, all the other outputs from
the master sync generator would be correct.
 
Later sync generators were GPS disciplined.
 
BTW... our later model analog transmitter was GPS locked
with one of the original HP boxes.  I remember ordering the
HP and then WAITING forever for it to arrive.  ;-)
 
In the interim, the transmitter ran on it's TCXO box.
 
We had twice yearly frequency measurements done
by a monitoring service up the coast.
 
73
Don
W4WJ
 
 
In a message dated 3/31/2018 11:04:12 AM Central Standard Time, k8yumdoober at gmail.com writes:
 
 I'e always been curious as to why TV stations did not lock at least
their in-house equipment to the network feed as a means to avoid
spending money on frame syncs. Remote coverage, on the other
hand, would of course open a new can of worms.

But compared to the cost of building and powering a TV station and
associated studios etc, a Rb or three cost a mere drop in the bucket
to buy and maintain, so I'm baffled as to why stations in general did
not at use them on a regular basis.

Dana


On Sat, Mar 31, 2018 at 12:43 AM, Hal Murray <hmurray at megapathdsl.net>
wrote:

> > As noted earlier, color burst references were a big deal a long time ago.
>
> Thanks. I was fishing for something modern, maybe a bit clock out of the
> digital receiver.
>
> I'm assuming that the digital stream is locked to the carrier. That may
> not
> be correct.
>
>
> --
> These are my opinions. I hate spam.
>
>
>
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