Hi > On Aug 6, 2020, at 7:28 PM, Forrest Christian (List Account) > <[email protected]> wrote: > > If you look at generally-available GNSS PNT solutions, you'll find a few > failure modes: > > 1) Loss of a satellite (or two). This is why the constellations have more > satellites than is strictly necessary, so not a big deal. > > 2) Loss of control/failure in the control system/constellation wide > software failure, aka the recent Galileo failure. This is why you have > multiple GNSS constellations. > > 3) Ground based interference (jamming, spoofing), etc. This is why you > need a terrestrial backup, which doesn't really exist. > > For timing, I wouldn't be opposed to someone flying (or adding a payload > to) a couple of geostationary satellites which live in a separate band from > GNSS. It would be interesting to be able to put up a small satellite dish > and get a highly reliable and hard to interfere with timing alternative to > GNSS. I know there are two way time transfer options out there, I'm more > thinking basically a fixed-location cesium clock in the sky.
Right now GNSS systems run in somewhere between 3 and 5 “bands” depending on how you count them. Various chunks of spectrum between 1 and 2 GHz get used by this or that system. Bob > > But, a good quality terrestrial option would be useful too. > > On Thu, Aug 6, 2020 at 3:40 PM Bob kb8tq <[email protected]> wrote: > >> Hi >> >>> On Aug 6, 2020, at 4:40 PM, jimlux <[email protected]> wrote: >>> >>> On 8/6/20 9:17 AM, Taka Kamiya via time-nuts wrote: >>>> Someone in this thread mentioned "at least 2 satellite time and >> frequency solutions" exists already. I only know of GPS (GNSS) >> constellations. What's the other? >>> >>> Transit? >>> >>> I don't believe they are still operational, though. >>> >>> >>> I wonder if one might be able to pick up time/frequency from a >> commercial TV broadcast transponder. The transponders on the satellite are >> typically bent pipes (for C-band anyway), I would assume that the uplinks >> may or may not have stability comparable to terrestrial broadcast. >>> >>> One problem is, of course, that the satellites aren't in a stable >> location (at least on a "meters" scale) - but one could certainly do >> "common view" kinds of time transfer. >> >> Another couple of “up in the air” question: >> >> Some of the systems transmit “stand alone” signals in each of two or three >> different bands. Does each >> band count as a separate time source? >> >> If you know your location already, each sat in these systems can be a time >> source all by it’s self. Do they >> each count? >> >> I guess is depends a lot on just how you look at redundancy …. >> >> Bob >> >> >>> >>> >>> >>> >>>> --------------------------------------- >>>> (Mr.) Taka Kamiya >>>> KB4EMF / ex JF2DKG >>>> On Thursday, August 6, 2020, 12:01:27 PM EDT, paul swed < >> [email protected]> wrote: >>>> Magnus >>>> Its honestly by luck that I know anything. From the bits I have read >> Europe >>>> seems far closer to eLORAN then we are. Perhaps 6 months ago the US >>>> performed a series of tests 2 eLoran solutions and something like 6 or >> more >>>> satellite solutions. I know the old Iridium satellites were in the tests >>>> and some other LEO satellites. >>>> But thats about it. >>>> What we need is a cheap SDR LORAN C sniffer. Low power runs 24 X 7 and >>>> turns a LED on if the stations active. >>>> Oh well another project in the someday pile. >>>> Regards >>>> Paul >>>> WB8TSL >>>> On Thu, Aug 6, 2020 at 2:42 AM Magnus Danielson <[email protected]> >> wrote: >>>>> Hi Paul, >>>>> >>>>> I only ask as you seem to track this thing the best here on time-nuts, >>>>> as far as I have seen, such that it is your emails that keeps me best >> up >>>>> to date with the progress. >>>>> >>>>> Cheers, >>>>> Magnus >>>>> >>>>> On 2020-08-05 19:21, paul swed wrote: >>>>>> Hi Magnus been a while since have emailed. >>>>>> Its one site that was a test transmitter. Its in New Jersey, USA. >>>>>> The goal of the testing I believe is to establish the viability of an >>>>>> alternate PNT reference to GPS. Additionally the ability to >> communicate >>>>>> some level of message broadcast. This should be identical to >> proposals I >>>>>> have heard of in Europe. >>>>>> But I have no direct relationship to any of this. Like you, a very >>>>>> interested observer and hope that eLORAN wins the battle. >>>>>> Unfortunately there are many alternate proposals such as using other >>>>>> satellites. Hmmm if I wanted to advance my career in the Air Force or >>>>> Space >>>>>> Force (Yes thats actually real now). >>>>>> Would I select the lowly reliable as heck eLORAN at sub $100 M/year to >>>>>> operate. Or the glorious space based proposals in $B region. Never >> mind >>>>>> that at least 3 countries now have demonstrated killer satellites. >>>>>> Sorry for that editorial. >>>>>> Regards >>>>>> Paul >>>>>> WB8TSL >>>>>> >>>>>> On Wed, Aug 5, 2020 at 11:04 AM Magnus Danielson <[email protected]> >>>>> wrote: >>>>>> >>>>>>> Hi, >>>>>>> >>>>>>> Do you know that they would do test with two actual transmitter >> sites? >>>>>>> >>>>>>> Cheers, >>>>>>> Magnus >>>>>>> >>>>>>> On 2020-08-05 16:00, paul swed wrote: >>>>>>>> Hello to fellow time nuts. >>>>>>>> Warm up those old Austrons. eLORAN out of New Jersey has been on the >>>>> air >>>>>>>> intermittently prior to a test run next week. Due to the storm they >>>>> have >>>>>>>> lost power and should have it back today or tomorrow. >>>>>>>> The intention will be on the air operation till the 20th. That's a >> long >>>>>>>> run. Nice. >>>>>>>> Seems the Austron 2100s can be had for reasonable money these days >>>>> also. >>>>>>>> Enjoy. >>>>>>>> Paul >>>>>>>> WB8TSL >>>>>>>> _______________________________________________ >>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>> To unsubscribe, go to >>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>>> and follow the instructions there. >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- [email protected] >>>>>>> To unsubscribe, go to >>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>> and follow the instructions there. >>>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- [email protected] >>>>>> To unsubscribe, go to >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>> and follow the instructions there. >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >>>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > > > -- > - Forrest > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
