[time-nuts] Loran in the US

Bob Camp lists at rtty.us
Thu Mar 8 23:16:13 UTC 2012


Hi

SDH/SONET generally is line timed rather than GPS locked. It's ultimate authority is the Stratum 1 above it... With CDMA framing, GPS time is actually the ultimate authority.  With GSM (as with the CDMA carrier frequency) a free running oscillator is generally "good enough".

Bob



On Mar 8, 2012, at 5:27 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> On 03/08/2012 11:21 PM, Bob Camp wrote:
>> Hi
>> 
>> Should be *very* interesting to watch if they try to legislate something
>> like that...
> 
> Indeed.
> 
> There are different telecom needs. CDMA isn't everything.
> 
> SDH/SONET goes under G.811, meaning within 1E-11 in frequency.
> GSM should be within +/- 50 ppb, but long-term should be like SDH/SONET.
> etc. etc.
> 
> Cheers,
> Magnus
> 
>> Bob
>> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>> Behalf Of Poul-Henning Kamp
>> Sent: Thursday, March 08, 2012 5:10 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Loran in the US
>> 
>> In message<D20D95B53D5C40F5ACA05DF98FDB9F08 at vectron.com>, "Bob Camp"
>> writes:
>> 
>>> If they are backing up GPS for telcom, then CDMA timing is the most likely
>>> target. That gets them to 10 us max and<  1 us typical. Of course somebody
>>> would have to buy the gear to actually *use* it to do any good... (yes I
>>> could and have gone on and on about that topic).
>> 
>> Well, they do actually regulate telecoms, so they may simply be told that
>> it will be a condition for their licenses.
>> 
>> That happened with respect to power backups for cellular towers
>> after Katrina showed the inadequacy of 3 hours lead-acid backup.
>> 
> 
> 
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