-------- paul swed writes: > The reason for 3 Cesiums at many stations is that > the stations were dual rated. A station worked in two or more different > chains so might be a Master. Sorry, but that explanation makes no sense ? Multi rated LORSTA's still only had one transmitter and one pulse generator, and it was up to the pulse control system to figure out when to send which pulses. (As far as I remember there were also tripple rated stations?) (The usual policy was that M to priority over S and competing S would alternate, but there were exceptions to that rule.) The pulse control system was entirely separate from the reference frequency stuff and having fewer or more Cs units would make no difference in any way for pulse generation. As far as I know, all stations had three Cesiums for redundancy, maintenance and cross-checking, and that was all there was to that. > Here is the funny thing, URSA-NAV made a statement long ago that I > remember. You could locate position with 1 station. That is physically impossible until you add something else to hold at least one other degree of freedom fixed. (For instance if you have a clock, you can measure the distance to the transmitter.) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.

The 3 cesiums were a cluster for high availability. Each station had them so that they could also act as a master for a second chain. I also believe there were some triple rated stations. Nothing to do with the Cesiums accept to maintain accuracy. Agree on the single station position fix. It was said and never made sense to me. Paul On Sat, Dec 7, 2024 at 11:12 AM Poul-Henning Kamp <phk@phk.freebsd.dk> wrote: > -------- > paul swed writes: > > > The reason for 3 Cesiums at many stations is that > > the stations were dual rated. A station worked in two or more different > > chains so might be a Master. > > Sorry, but that explanation makes no sense ? > > Multi rated LORSTA's still only had one transmitter and one pulse > generator, and it was up to the pulse control system to figure out > when to send which pulses. > > (As far as I remember there were also tripple rated stations?) > > (The usual policy was that M to priority over S and competing > S would alternate, but there were exceptions to that rule.) > > The pulse control system was entirely separate from the reference > frequency stuff and having fewer or more Cs units would make no > difference in any way for pulse generation. > > As far as I know, all stations had three Cesiums for redundancy, > maintenance and cross-checking, and that was all there was to that. > > > Here is the funny thing, URSA-NAV made a statement long ago that I > > remember. You could locate position with 1 station. > > That is physically impossible until you add something else to hold > at least one other degree of freedom fixed. (For instance if you > have a clock, you can measure the distance to the transmitter.) > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > phk@FreeBSD.ORG | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. >

Hi You have the classic problem: If you only have two clocks and they disagree … which one is wrong? No way to know. If you have three clocks and they disagree, you can at least make a guess. All of these stations had to be able to run for a bit “on their own”. Modern cell sites are no different. Without some sort of “holdover” ability, system reliability is very hard to achieve. With stations in areas that might be hard to get to for “a good long while” the holdover duration would be a lot more than that cell tower …. Bob > On Dec 7, 2024, at 11:33 AM, paul swed via time-nuts <time-nuts@lists.febo.com> wrote: > > The 3 cesiums were a cluster for high availability. Each station had them > so that they could also act as a master for a second chain. > I also believe there were some triple rated stations. Nothing to do with > the Cesiums accept to maintain accuracy. > Agree on the single station position fix. It was said and never made sense > to me. > Paul > > On Sat, Dec 7, 2024 at 11:12 AM Poul-Henning Kamp <phk@phk.freebsd.dk> > wrote: > >> -------- >> paul swed writes: >> >>> The reason for 3 Cesiums at many stations is that >>> the stations were dual rated. A station worked in two or more different >>> chains so might be a Master. >> >> Sorry, but that explanation makes no sense ? >> >> Multi rated LORSTA's still only had one transmitter and one pulse >> generator, and it was up to the pulse control system to figure out >> when to send which pulses. >> >> (As far as I remember there were also tripple rated stations?) >> >> (The usual policy was that M to priority over S and competing >> S would alternate, but there were exceptions to that rule.) >> >> The pulse control system was entirely separate from the reference >> frequency stuff and having fewer or more Cs units would make no >> difference in any way for pulse generation. >> >> As far as I know, all stations had three Cesiums for redundancy, >> maintenance and cross-checking, and that was all there was to that. >> >>> Here is the funny thing, URSA-NAV made a statement long ago that I >>> remember. You could locate position with 1 station. >> >> That is physically impossible until you add something else to hold >> at least one other degree of freedom fixed. (For instance if you >> have a clock, you can measure the distance to the transmitter.) >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> phk@FreeBSD.ORG | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

I was in the navy in submarine navigation. Before I got out, they upgraded our LORAN C receiver to a BRN-5 from a WPN-3. With this we could get a good position fix with two stations. We had two cesium standards for navigation. When in refit we had to track LORANC, only one station required, to determine the drift rate of our Cesium standard. This drift rate was entered into the nav computer. We received messages informing us of the drift rates of the LORANC station cesium standards. This information was entered into the nav computer. After the calibration on board, we only needed two stations to get the fix. We did not need a master station. This was referred to as phase shift LORAN. This was 40 plus years ago and that is about all that I remember. Glenn ETCS(SS) USN retired On 12/7/2024 10:51 AM, paul swed via time-nuts wrote: > I believe the stations all had the 3 Cesiums. > But that said (I am not a navi-guesser) two stations leave ambiguity in > position as I recall. > The third eliminates it. The reason for 3 Cesiums at many stations is that > the stations were dual rated. A station worked in two or more different > chains so might be a Master. > Here is the funny thing, URSA-NAV made a statement long ago that I > remember. You could locate position with 1 station. > Never made sense to me but what they were doing with eLORAN and higher > resolution perhaps does allow that. > I'll snip a bit of a log and attach it later today to share. > Paul > > On Sat, Dec 7, 2024 at 1:53 AM Poul-Henning Kamp via time-nuts < > time-nuts@lists.febo.com> wrote: > >> Brooke Clarke via time-nuts writes: >> >>> I thought just before LORAN-C was turned off they had atomic clocks at >> each station rather than have the slave station >>> timing determined by the chain master station. >> Warner is the best person to talk about that, because he was involved in >> the last >> control system upgrade. (My understanding is that the Cs's were steered >> to GPS.) >> >>> That would allow using each transmitter, like a GPS receiver uses each >> satellite, independently of each other. So, you >>> can get a position fix using two or more stations, even if they are from >> different chains. >> >> You could always do that, if your receiver was advanced enough. >> >> The question was what your precision would be like. >> >> My understanding is that GPS-steering the stations was also hoped to >> improve that aspect. >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> phk@FreeBSD.ORG | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> _______________________________________________ >> time-nuts mailing list --time-nuts@lists.febo.com >> To unsubscribe send an email totime-nuts-leave@lists.febo.com > _______________________________________________ > time-nuts mailing list --time-nuts@lists.febo.com > To unsubscribe send an email totime-nuts-leave@lists.febo.com -- ----------------------------------------------------------------------- Glenn Little ARRL Technical Specialist QCWA LM 28417 Amateur Callsign: WB4UIVwb4uiv@arrl.net AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"