Hi I believe the 50 ns is the “as transmitted” signal from the tower. The “as received” signal after going through all the various gyrations is not that good on a ~1 second basis.
==== One of the gotchas here is that we lump “systems” into one giant bag. That’s not a good way to analyze things. One system may be quite happy with 10 ms timing another may be happy with 10 us and yet another may die completely at 1 us and only run right at 100 ns. All of that is on a 2 second basis for CDMA (they time every other second). By far the biggest / baddest / most venerable system out the that uses GPS timing is the cell tower system. They started out back in the 80’s with a 10us max timing / 1 us running spec on CDMA. AFIK they were the first major system to adopt GPS time as their reference (rather than UTC). This worked out fine for a few decades while companies got a lot of towers built. People started using those systems and they became congested. Others started streaming video over them and they ran out of bandwidth. Upgrades followed. There have been a lot of them. Much of what we TimeNuts buy on the surplus market comes to us as a result of older systems being scrapped out. The latest set of upgrades does / will / is getting them into the sub 1 us range at the end of holdover. In normal operation they are spec’d at 100 ns worst case. To do that, you need a timing source in the roughly 10 ns range. No you don’t see those GPSDO’s on the surplus market. You will see them someday …. Again, they went this way a decade ago. Rolling that all back …. not at all easy. Are there other systems that have issues with sync? Of course there are. There also are a lot of instances where miss-configuration ( or junk implementation) is a much bigger issue. Sorting that all out requires a deep dive into the timing of each individual system / implementation. No two systems do things quite the same way. Unless you want to deal with the numbers and the implementation details, simply moaning and groaning isn’t going anywhere. Bob > On Sep 8, 2018, at 3:23 AM, Hal Murray <hmur...@megapathdsl.net> wrote: > > > kb...@n1k.org said: >> You are not trying to run a cell system when checking your local oscillator >> against LORAN. > > The eLoran committee said 50 ns. Is that good enough for cell towers? > > Too bad it isn't up so we could collect some data. > > > -- > These are my opinions. I hate spam. > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
