[ntp:questions] Clock accuracy & auto setting : digital television does a crap job of providing time services...

Danny Mayer mayer at ntp.isc.org
Thu Apr 27 20:06:53 UTC 2006


This probably belongs more in the NTP WG and/or hackers than here since
it sounds like you are looking for enhancements to the NTP model.

Danny

Max Power wrote:
> In North America, the FM RDS time service is of very low quality.
> In Europe (I understand) this is not the case with RDS.
> Stations running RDS should be mandated by law to provide a quality 
> service -- based on transmitter power and coverage area.
> Over time RDS's time service should be uniform.
> DRM (on MW and SW) time service is of a lower quality than RDS -- but could 
> be upgraded with a specialized "80 bit" NTP-UNIX time packet.
> 
> ATSC and DVB-T (& DVB-H/M) need a uniform ~"80 bit"...~"128 bit" time packet 
> service that is well thought out.
> Futureproofing is important, so probably 128 bits or more is preferable.
> 
> LF time services are OK, and are necessary over large transnational 
> regions -- like Sub Saharan Africa, Australasia and South America ... but 
> any new LF service needs to be more technologically advanced than WWVB, MSF 
> or DCF77 and its Swiss twin. In these regions 10 LF frequencies need to be 
> allocated, but the signal to be transmitted needs to be more modern than 
> WWVB or DCF77 -- maybe using some form of low complexity PSK or low 
> complexity QAM and 240 hz to 480 hz of bandwidth. The signal must be 
> futureproofed -- as above.
> 
> I wish I had all of the email addresses of the Canadian National Research 
> Council -- so that I could email them my CHU upgrade proposal at
> * http://CBC.am/CHU.htm
> * This proposal probably, if implemented -- would require a signal upgrade 
> to account for 2 transmitters on all of the frequencies used.
> * A properly designed signal upgrade could make CHU a more powerful 
> [technological design] than WWV[H] -- but this would probably require 2 or 3 
> years of experimentation. I would love to see support for high speed ECC 
> polytone and MD63 (MD?) with its Walsh coding.
> 
>>>> ATSC time is always late ?
>>> ========================
>>> ATSC and DVB-T (DVB in general) are devoid of a 64 bit (or 80 bit) clock
>>> packet (based on NTP and 'Unix Time').
>>>
>>> For people to be forced to rely upon GNSS (Glonass, GPS, Galileo) for a 
>>> time
>>> signal is rather immoral when TV transmitters (and radio too, remember 
>>> RDS)
>>> pump out many megawatts of signal each day (globally).
>> /////////////////////////////////////////////////
>> Immoral?  That's a bit strong, innit?  You don't NEED to rely on 
>> satellites for
>> time signals.  There are many LF radio time signals, such as WWV, WWVB, 
>> WWVH,
>> CHU, MSF, DCF77, and others.  CDMA cell phone towers broadcast a time 
>> signal. 
> 
> 
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