On 2021-01-27 12:58, Fred Gleason wrote:

On Jan 26, 2021, at 19:03, Brian Inglis <Brian.Inglis@SystematicSw.ab.ca <mailto:Brian.Inglis@SystematicSw.ab.ca>> wrote:

...

Digital processing mainly compression/decompression delays in the common modern broadcast chain results in time announcements, transitions of minutes, audio "pips", clock tower chimes or bells, varying by eyeball and wristwatch measurable amounts from accurate time sources. Some articles talk about timing broadcast sources to determine which earlier "pip" signals the correct time. Apparently coordinating multiple regional sources in e.g. commentaries, discussions, or now virtual talk shows, requires time code calibration and compensation, so that discussions can appear natural; more so than many remote news reports which can show very pronounced delays, probably due to cellular mobile or wifi sources and internet routes. Satellite links add only up to 250ms each round trip. Many articles lack date stamps so it is difficult to know even if the BBC still transmits legacy analogue AM or FM with accurate "pips" or if stations are mainly DAB in the EU and UK.

It’s not just in the EU or UK. Digital modulation methods in common use on broadcast air chains in the US (both audio and video) can easily add up to several *seconds* of latency per hop. This can be the case even when the final delivery link to the receiver is ‘analog’ —e.g. amplitude modulation (‘AM’) via medium wave. Effectively, all audience-facing time marks on such broadcasts should be treated as being precise only to the nearest minute.

https://en.wikipedia.org/wiki/Greenwich_Time_Signal#Similar_time_signals_els... I'm unaware of broadcast network time signals and their accuracy in NA other than CA CBC Radio One at 13:00 ET, and NR have disclaimers about those and telephone time and talking clocks possibly having one or two ~0.25s satellite hops added, which makes them useless: https://nrc.canada.ca/en/certifications-evaluations-standards/canadas-offici... https://nrc.canada.ca/en/certifications-evaluations-standards/canadas-offici... The telephone and broadcast time data require obsolete Bell 103 modem decoders and suffer from unknown telco or shortwave propagation or ionospheric delays and conditions: https://nrc.canada.ca/en/certifications-evaluations-standards/canadas-offici... https://nrc.canada.ca/en/certifications-evaluations-standards/canadas-offici... -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised. [Data in binary units and prefixes, physical quantities in SI.]

On 1/27/21 11:58 AM, Fred Gleason wrote:

all audience-facing time marks on such broadcasts should be treated as being precise only to the nearest minute.

This topic came up during the famous trial of OJ Simpson in the 1990s, when they were trying to establish a timeline of events. Here's a section from the 1995-07-11 trial transcript: MR. DARDEN: Miss Harman, the times that you've given us today, those--the accuracy of those times depend on the accuracy of someone else's kitchen clock; is that correct? MS. HARMAN: And-- MR. SHAPIRO: Objection. THE COURT: Overruled. MS. HARMAN: And desk clock. Yes, it would. MR. DARDEN: Okay. And as well as the accuracy of the digital clock in your vehicle; is that correct? MS. HARMAN: Yes, it would. MR. DARDEN: And so if those clocks are one or two or more or less minutes off, then your time would be off, wouldn't it? MS. HARMAN: It would, except I usually set the clock to KFWB. So I feel confident that the clock in my car was accurate. Afterwards, I remember reports that KFWB's time signal was more accurate than that of KNX, their main news rival, and that KFWB's marketing tried to make hay of this. In the long run it was all for naught, though: KFWB's corporate owner bought the much more powerful KNX and then eventually sold KFWB, which is now airs classic regional Mexican music. And as far as I know, KNX's audio time signal is no more accurate now than it was in the 1990s.

<<On Wed, 27 Jan 2021 15:02:30 -0800, Paul Eggert <eggert@cs.ucla.edu> said:

And as far as I know, KNX's audio time signal is no more accurate now than it was in the 1990s.

Most CBS owned-and-operated radio stations installed "HD Radio", which requires an eight-second delay in the analog audio to match the compression delays on the digital side. (CBS Radio's then national VP of engineering, Glynn Walden, was heavily involved in the creation and promotion of the "HD Radio" system.) Receivers may add additional decoding delays so long as they delay analog audio an equal amount. (This allows for "seamless" cross-fading between the analog and digital signals at the fringes of the digital coverage area.) The encoding delay for "HD2" and other low-bandwidth subchannels is even longer, about 30 seconds (there's no blend-to-analog issue there, just the encoder). Even before HD Radio, CBS affiliates that carried the network news at the top of the hour would normally take the "bong" from the network feed, via satellite. However, CBS stations running a talk format would not normally dump the profanity delay for the news, so the network "bong" would be delayed another seven to fifteen seconds. Some talk stations chose to insert their own top-hour tone after the profanity delay, often at the transmitter. (Aside: When Westinghouse bought CBS, this combined Westinghouse's all-news stations with CBS's all-news stations in several major markets, including Los Angeles; other than New York, the weaker of the two stations ended up changing formats. But after Westinghouse changed its corporate name to "CBS", this had the effect that "CBS" owned a number of radio stations that were not affiliates of the CBS Radio Network -- the former Group W stations were primarily ABC Information Network affiliates if they had any network at all. ABC-I didn't broadcast a top-hour time signal, so those stations, like WBZ in Boston, already had their own local top-hour beeps if they wanted. WTIC in Hartford, which wasn't a Westinghouse station but did later become part of CBS Radio, famously kept its V-for-Victory Morse code interval signal from World War II. A few years back, CBS spun off its radio unit to Entercom, but kept the CBS Radio News network under the new name "CBS News Radio".) -GAWollman

Paul Gilmartin via tz said:

I'm changing my stance on Leap Seconds: yes, it's a means of keeping UTC synchronized with the earth's rotation. But I see no need. Fix UTC forever at TAI - 42(?) s and make desired adjustments in civil time. At some future date when the drift accumulates to several minutes, change my timezone from MST7MDT to MST7:15MDT. This can be coordinated with the Spring clock reset: every few centuries that can be +45 minutes instead of +60.

That's the leap hour proposal. I don't understand why so many people were against it. -- Clive D.W. Feather | If you lie to the compiler, Email: clive@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646

On Fri 2021-01-29T10:33:35-0700 Paul Gilmartin via tz hath writ:

I'm changing my stance on Leap Seconds: yes, it's a means of keeping UTC synchronized with the earth's rotation. But I see no need. Fix UTC forever at TAI - 42(?) s and make desired adjustments in civil time. At some future date when the drift accumulates to several minutes, change my timezone from MST7MDT to MST7:15MDT. This can be coordinated with the Spring clock reset: every few centuries that can be +45 minutes instead of +60.

The problem that originally brought us leap seconds was that the legal definition of a calendar day in most countries is one mean solar day, which means actually measuring the rotation of the earth. Representatives from countries with such laws could not approve the use of radio broadcast time signals deviating from that definition. Because UTC by that name has become the basis of legal time in most places it will be necessary to get consensus to change the definition of the calendar day. At the ITU-R WRC in 2015 the same issue arose when a number of countries objected to changing UTC in a way that redefined the calendar day. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m