I only have one idea. Something I thought of doing it myself but have not done
so, yet.
I think syncing locations with GPS or ntp is good enough for time
synchronization. But display could be problematic. As they make transition
from one program to another, 1 second overlap or 1 second of blank is quite
long. Listeners will certainly catch on to that.
I wanted a digital clock that has HH:MM:SS but below that are bar graph for
sub-second. Say 10th of a second, one LED representing 1/10th. That way, they
can count down and meet at 00 exactly enough for human perception. For this
kind of thing, fast flying 10th digit isn't really useful as it's awfully hard
to read, let alone read and do something else, like think of a word to fill
that last 1/2 second.
I would think this kind of thing is easy enough to implement either as a
hardware or an application on Windows/Linux workstation. Whatever the device
to use, it must be synced with the master source. PC's clock can go off by 20
seconds per day quite easily. Even server class machines close to million
dollars use cheap 32KHz fork crystal.
---------------------------------------
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Friday, October 18, 2019, 4:00:41 PM EDT, Eric Scace <[email protected]>
wrote:
I fear that I am developing a reputation for bringing to the list rather
oddball questions. In my rôle as agent provocateur, therefore, here is another
such problem.
Questions for you are at the end. Thanks for your thoughts,.
— Eric
Issue:
A community broadcast radio station with multiple studio locations wishes to
improve the display of time-of-day throughout the station’s operating
environments. Its current legacy approaches (described below) cause problems
such as:
on-air presenters fail to smoothly segue into scheduled program feeds (e.g.,
BBC news) because the studio clock is “a little off”… and because the studio
clock is digital. [Quick: how many more seconds can you speak before the top of
the hour when a digital clock shows 4:59:42? Watching an analog stepping second
hand is much easier in this situation.]
computers that automatically capture audio programs to files in storage
sometimes truncate the start or end of the program because the computer’s idea
of time-of-day disagrees with that of the program source.
desktop computers throughout the station, including in production studios, all
render slightly different versions of time-of-day to their users.
servers (e.g, for streaming, for archiving shows) are similarly in cheerful
disagreement as to time of day.
wall clocks studios in one city show a different time to their engineers than
the studios in another city, rendering handoffs more complicated. Ditto for
remote broadcast sites, and even between studios in the same site.
requires manual intervention to bring the most egregious systems back to some
semblance of reality
Background & existing situation:
Commercial broadcast stations have more money and technology to solve these
problems. In contrast, “community radio” stations have limited funds and are
largely staffed by volunteers (like me!).
In this case, the existing systems are a hodgepodge:
mostly Windows OS PCs, with a couple of Macs
Linux servers
mash-mash of wall clocks, the best of which is a LaCrosse WWVB digital in the
primary on-air studio. The WWVB signal is more than adequate but the LaCross
display format is sub-optimal for studio use.
Goals: (first pass)
minimum accuracy requirement: time-of-day displayed within ±0.1 second of UTC
timescale. (Two clocks both falling outside this range will cause program
handoffs to be uncomfortably tight or loose.)
no manual intervention required for summer/winter time transitions
no manual intervention required for leap seconds
leap second:
no smearing (minimum requirement)
accurate leap second display (desirable but unlikely to be achievable)
desirable consistency goal: time-of-day displayed within ±0.025 second
throughout each site. At this level, two adjacent clock displays will not be
perceived as out of step by a person.
presentation goals: studio/remote broadcast control point time-of-day displayed
in both analog (with stepped seconds hands) and digital form (preferred H:MM).
If digital form includes seconds, the seconds digits should be visually
separated; e.g..smaller. A presenter can then, at a glance and without
confusion, announce the time (“four twenty-three”) from the digital display.
Date in form “Oct 17 Thu” available.
medium-term desirable: displays continue within specs for accuracy/consistency
across power cutovers (to/from generator) and public Internet outages.
maintenance goals:
"eschew emergencies”: no one should have to rush to the station in the middle
of the night, nor drop what their doing during the day, because time-of-day
display has failed or gone out-of-spec.
standardize on the same hardware/software everywhere
identical hardware allows more cost-effective 1:N sparing
identical hardware/software means less confusion and less training for
volunteers. (There are a large number of volunteers who use these systems, and
most contribute time less than once per week. Consistency and
straightforwardness in the toolkit improves the quality of on-air results.)
not too costly
try to avoid stringing a lot of new cabling around… but such cabling needs are
recognized as a one-time investment, so this preference does not eliminate a
cable-based solution that has other operational/maintenance advantages
Potential approaches:
potential short-term:
desktops and servers: better NTP configuration
NTP checks:
at least hourly?
verify NTP utility employs reasonable averaging of multiple NTP servers
use time.nist.gov <http://time.nist.gov/> and similar higher-quality NTP servers
some systems are on in-house Ethernet; others on in-house wi-fi
clocks:
replace with refurb iPads running a dedicated time-of-day display app providing
both analog and digital form. A refurb wall- or desk-mounted 13” iPad in
locking frame runs about $100. Smaller sizes can be mounted immediately
adjacent to or atop a studio mixing board.
remote field broadcast site: iPad over local wi-fi or cellular data?
IRIG displays could be awesome, but seem far more costly per display and
require pulling coax — and integrated analog + digital displays appear to be
less common. Two displays (one analog, the other digital) in each studio
provide some redundancy but costs go up fast.
NTP-clocks powered over ethernet could similarly be awesome, but are similarly
more costly and few integrated analog + digital displays exist.
medium term:
add in-house NTP server (with GPS and reasonable holdover plus battery backup)
on each city’s on-site LAN/wi-fi networks as primary source, with remote public
NTP servers as secondary. Many suitable models appear to exist, including the
ESE E-911 units mentioned recently. Only a few are needed: one for each site
plus sparing.
potentially increase the frequency of NTP synchronization for each
computer/display clock when a local NTP server has been installed.
Questions:
Are there other approaches that should be considered?
What NTP software should be used on Windows OS machines? Linux servers?
Mac OS allows one choice of NTP server but does not seem to provide for choice
of NTP update frequency. Is there a 3rd party software solution, or some other
parameter within MacOS that an admin can change to (a) establish a primary and
secondary NTP server, and (b) set the frequency of NTP updates?
If one were to use an iPad to display time-of-day, what iPad apps provide the
needed display formats, frequency of NTP checks, primary/secondary NTP sources?
For example, Atomic Clock Gorgy updates hourly and allows the user to choose
one NTP server group (e.g., time.nist.gov <http://time.nist.gov/>). It has an
analog seconds display format (circle of dots), digital H:MM (optional :SS),
and MMM D DDD — although one could quibble over the typography. However, the
display shows “SYNC” for a couple of seconds each hour while the NTP update
occurs, which would be disconcerting if it happens when a presenter/engineer is
in the midst of joining/cutting away from external program sources.
What have we overlooked?
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