[tz] CCTF survey on Time and Frequency Metrology - Telecom

[Brian Inglis]

On 2021-01-26 13:49, Hal Murray wrote:
> Brian Inglis said:
>> My reply suggested they divorce the time scales to allow business systems to
>> use  approximate POSIX like common law legal solar time as they ignore leap
>> seconds  one way or another; allow scientific systems to use atomic time and
>> ignore legal  solar time; and just ignore the ITU as broadcast radio time
>> signals (DCF/JJY/MSF/WWV/B/H) are unavailable most places, may need
>> equipment no longer  commonly available, and too low accuracy for modern
>> needs; other commonly  available sources are delayed to uselessness by
>> digital processing.
> 
> Could you please say more about the "delayed to uselessness"?

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.

BBC "pips" history:
http://tech-ops.co.uk/next/search_gcse/?q=GTS

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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