Hi
> On Feb 6, 2017, at 7:38 PM, Ruslan Nabioullin <rnabioul...@gmail.com> wrote: > > So any ideas on how likely it will be that eLORAN becomes deployed with at > least partial US coverage within the next 5--10 years? No, this is not the world as I would like it to be. It is the world we live in now and are likely to live in for the foreseeable future. If we are looking at it purely as a timing reference the outlook is not real good. Best guess about 1 in 1,000. I’m probably estimating that on the generous side. If there is some other magic use for the thing (or a couple dozen other uses) that might change the equation. Right now those other uses are not very obvious. Why the lousy outlook: 1) The way a system like this gets funded is for it to have a lot of users. It might also get funded if some crazy black project needs it. That’s not happening with Loran. Loran died in the first place due to a lack of users. 2) For a system like this to have a lot of users, you need to pass regulations requiring it’s use. That may seem odd, but that’s the way it works. Loran co-existed with GPS for a long time. GPS was *less* reliable back then than it is today. Using Loran for timing was a very rare thing outside a handful of labs. 3) To regulate it into major systems, it needs to have at least a country wide coverage and more likely a bit more than that. Without that there isn’t enough of a timing market to address. You need to retrofit it into every cell tower in the country (for instance). 4) Loran getting into buildings from a single site (even fairly close) … not so much if they are full of switching power supplies, you have a problem. You need to have *many* Loran transmitters. Cell timing is moving out of the “edge” and into the central hubs. That means buildings full of switchers. 5) Tying multiple time sources into a system costs big money. If you only have two clocks, how do you decide which one is wrong? Not an easy question to answer. That money has to come from somebody. Nobody wants to pay. The cell carriers have never been excited about investment that does not immediately result in more customers. 6) There are multiple competing “for pay” backup timing systems. Adding another one to the mix is pretty hard to justify. Even more so if you can “steal” timing off of one and not pay for it. That would be the case with an eLoran that works with all our old gear. 7) Like it or not, justified or not, cost effective (not), the world is hung up on space based systems. There is no excitement in 1950’s technology. 8) Loran for exact timing has some major issues with propagation delay. If your goal is the same as the system specs ( < 100 ns) that’s going to be a really tough nut to crack. Do they *need* < 100 ns? It’s in the spec … Will they keep studying it as long as they can get funding for the study? Of course they will. How long will people keep pitching in for that funding … could be years. Five to ten year studies that go nowhere are not at all uncommon. Right now we have multiple broadcast time sources running 24/7 at various frequencies with various coverage zones. As far as I know *none* of them are tied into major systems. That’s just the way it is, and it’s nothing new. Even in military systems, multiple time sources into a system is a very rare thing. In commercial systems … Again, I’m not arguing that this is an ideal world. Bob > There exists a solid company working on its R&D (UrsaNav), apparently > increased awareness in government, and UrsaNav entered into a partnership > with Spectracom for integrating its UN-152B (modern SDR-based eLORAN, > Loran-C, and Chayka frequency and time transfer receiver) for GNSS fallback, > which has been tested for commercial applications (e.g., NYSE), so apparently > there is some commercial demand (I have been told by an engineer at Google > that they are aware of this for Spanner and their other R&D projects > requiring time metrology, but have not decided yet). > > -Ruslan > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
