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.

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@megapathdsl.net
wrote:

Hi

My comments really were a bit brief…. indeed there are clocks in the modern
signals. Those clocks come over as part of the signal you get. The must be a
way to build something that would get at those clocks.

You still have the same basic issue as with the “old” signals. Does it go through
a satellite link? Does it come straight from a Cs based studio? Does it get regenerated
against an OCXO or a TCXO? All of that will make it a good reference “some of
the time”. Working out when that is …. good luck.

You probably would do better to build a gizmo to pull timing off you local cell towers.
The hardware to do it is relatively well documented. As long as you are careful about
which system you use, the timing should be GPS based ….

Ok, so the issue is an alternative to GPS? Well one of the “likely sources” for
a modern TV broadcast setup would be a GPSDO. The same thing for the modern
digital FM broadcast setups. I have good reason to make this claim ….. :)

Bob

On 3/30/18 10:43 PM, Hal Murray wrote:

Maybe locked, but probably not in a 'integer number of cycles per
symbol' sense, more in the "derived from the same master 10 MHz
reference" sense.

All stations use the same data rates, but have different carrier
frequencies, and the carrier frequencies are the same ones we've always
had, which don't necessarily have nice ratios between them.

When the transition to digital only happened, I happened to ask a ham friend who was chief engineer at the local Fox station what they were doing with all their gear. He said probably taking it to a hamfest.
I said if you chuck your rubidium or cesium standard let me know. He started laughing and said we don’t have anything that precision, you’d be lucky for it to be a TCXO.

Chris
KD4PBJ

Hi

To a great extent it depends on who was running the tech side of things. If the guy
in charge dug into it, they may have had a pretty fancy timing setup. If it was a
“don’t bother / don’t dig / not very broken” sort of thing, the setup may have been
pretty crazy.

Bob

On Sat, Mar 31, 2018 at 9:38 AM, Bob kb8tq kb8tq@n1k.org wrote:

Commercially-made cellular reference receivers obviously do exist (IT
folks tend to love them due to there being no need for outdoor antenna
requirements).

-Ruslan

--
Ruslan Nabioullin
Wittgenstein Laboratories
rnabioullin@gmail.com
(508) 523-8535
50 Louise Dr.
Hollis, NH 03049

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@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@megapathdsl.net
wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Yes I actually purchased two such devices from Ebay a while back.  (They contained nice PRS10 Rb oscillators.)

Mark Spencer

Aligned Solutions Co.
mark@alignedsolutions.com
604 762 4099

In the mid-1970's (when I was an EE student in college) I built a simple
setup to compare the US color burst signal (3.5795454.. MHz) from an old
vacuum tube color television set with a commercial surplus 5 MHz OCXO
(probably from Bliley). The color burst frequency was exactly:315/88 = (63 * 5)/88  = 3.5795454.. MHz

So I built two  frequency dividers.  I think I used 7490 or 7492 TTL
IC's and a few gates. I divided the color burst signal from the TV set
by 63 to get a 56.81818.. kHz signal and compared the phase to the 5 MHz
oven oscillator divided by 88 (also 56.81818.. kHz). I had a surplus
Tektronix RM45A oscilloscope with a CA plug-in (24 MHz bandwidth) and a
surplus well-used analog chart recorder.
With this setup I could see the phase of the color burst signal of the
three major US networks (CBS, NBC, and ABC) when their local affiliate
station (Austin, Texas) was broadcasting a network feed. This was before
frame resynchronizers, so there was a glitch in the phase (and often a
frequency change which was easily detectable) when they switched away
from the network feed.
By late 1976 I was out of college at my first job (Rohdes-Groos
Laboratories), where I was the only engineer. My boss wanted us to
manufacture a low-cost frequency reference for calibration labs using
the color burst signal to discipline a local crystal oscillator. At that
time (mid to late 1970's) the three networks used rubidium or cesium
atomic frequency references to control their network feed color burst
and horizontal sync signals. NBS (later NIST starting in 1988) measured
the frequency error (and maybe the phase error - I forget) of each of
the networks on a daily basis, and published these in a document
released shortly after the end of each month (as I remember it). So you
could make local measurements and a few weeks later you could correct
for the measured error of that feed compared to the NIST reference. The
general idea was to average or curve fit the NBS errors for some
interval (a week or a month) and compare that against local measurements
you made during that interval. If the frequency error was stable or
linearly drifting you could make reasonable predictions for future
measurements, so you didn't have to wait for the NBS error reports to
get good results. We had a WWVB receiver and rubidium standard in our
office, so we could check the performance of our project.
A local company in Central Texas (unrelated to my company) developed a
simple product which detected the phase glitch in the color burst or
horizontal sync signal when the network feed phase changed. This was
used with other information to switch local programming (commercials,
etc.) into or out of the transmitted signal.
The first problem with using the network feeds to distribute frequency
was that at least one network started to look at the NBS frequency/phase
deviation reports and, thinking they were going to improve this process,
tweaked the magnetic field fine adjustment on their atomic standard in
an attempt to discipline the frequency. Of course, this removed the
ability to predict the behavior of that feed, since it might walk up or
down in frequency at any time the network tweaked their standard. So
everyone wanted the TV networks to stop tweaking their standards and
just let them slowly drift in a temperature stable environment.
But the worst problem was the introduction of frame resynchronizers.
This meant you were now measuring the local station frequency reference,
which wasn't usually all that good. So we cancelled the color burst
frequency standard project.--
Bill Byrom N5BB

On Sat, Mar 31, 2018, at 4:00 PM, Don Murray via time-nuts wrote: