Hal Murray wrote: >Has anybody tried using the phone company as a frequency reference? > >Are the telco master clocks locked to GPS or national frequency sources? Or >do they just use their own Cesium box? > > Yes to all of the above. It depends on the telco. All of them "should" meet the 10E-11 requirement over a "long" interval
>Is that a useful way to get a good clock without a GPS antenna? > > > Probably, if you filter the jitter and wander with a reasonably good crystal oscillator >I worked with T1 many years ago. It wouldn't be hard to extract a signal to >feed to a PLL. > > You could lock an oscillator to the T1 rate and then divide that down to something like 8 or 4 KHz and use that to discipline you "precision" oscillator >Has anybody done that and collected data? I'd expect lots of short term >jitter and wander but the long term should be pretty good. > > > The telco's do that all the time. The worst wander I have seen was about 200 NanoSeconds over a few minuets time. There was a lot of data available at one time. SONET (fiber optics) had a problem with step changes in phase on the payload.. Don't know how that was resolved >Does anybody know how DSL works? If I poke around with a scope in my DSL >modem/router, will I find a clock locked to the telco's master clock? > >How many different versions of DSL are there? > > > > I haven't worked in this field for about 16 years so anything I type is from that time frame. Bill K7NOM _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
