[time-nuts] eLORAN will be on the air GRI 99600

Wed Aug 5 23:45:41 UTC 2020

We seem to be going through another stage in our technological evolution
right now as far as redundancy goes.

To explain what I mean:

A long time ago things were so unreliable that everyone knew that you
needed two systems, even if one was the watch in your pocket and a compass
and sextant for PNT.

As technological systems got better and better somehow we forgot this
lesson.   GPS is so reliable that people don't even think about the
possibility that it might go away, so we got complacent about maintaining
the old systems to maintain a backup.  Things like LORAN C were cut for
'cost savings' reasons, since why keep a backup for a system that never
fails?  I can't fault the logic, assuming one buys the perfect
reliability premise (no I don't buy this as at all).

Recently it's become obvious there are lots of ways that our technology can
fail.   Not just GPS but I could cite other examples not relevant to this
list.   So we've now entered the phase where we're trying to figure out
what to do to regain the capabilities we carelessly discarded in the past
based on a false premise of the new stuff being perfectly reliable.

Fortunately for PNT, the US government definitely signaled that the
redundancy must be ground-based when they passed the "National Timing
Resilience and Security Act".  So hopefully we don't have to worry about
the second system being space-based.  Heck, we already have at least 2
space-based alternatives in orbit.

They were supposed to get this in place within 2 years, which I think means
the end of 2020 if I'm reading the dates right.   Since it's already
August, I doubt they'll meet the deadline.  Hopefully, with the testing
they're doing, it won't be much longer.

On Wed, Aug 5, 2020 at 4:15 PM paul swed <paulswedb at gmail.com> wrote:

> Jim
> Thanks for the insights. Oh I am not selling it for emp. I am simply saying
> no would be general wants a rusty old steel tower as a career booster. I
> remember when LORAN C was shut down the president said he was saving $36M a
> year. Thats drop in the old bucket. I also remember the LORAN C antennas on
> mobile tower sites for timing along with GPS.
> Thanks again Jim.
> Fire up that LORAN C receiver and see what you can hear.
> Regards
> Paul
>
> On Wed, Aug 5, 2020 at 5:41 PM jimlux <jimlux at earthlink.net> wrote:
>
> > On 8/5/20 12:40 PM, Tom Knox wrote:
> > > Hi Paul and Magnus;
> > > Not to mention one space EMP would kill all the Sat systems, where a
> > ground base system even if affected would be easy to access for repair.
> >
> > The vulnerability of GNSS systems to EMP attacks is not all that high -
> > GPS is, after all, a DoD essential system, and lives in a ridiculously
> > high radiation environment in MEO - They're also hard to neutrons (based
> > on published specs for components in the GNSS satellites).
> >
> > In most scenarios, LEO satellites get hammered, MEO and GEO not so much.
> >
> > https://apps.dtic.mil/dtic/tr/fulltext/u2/a531197.pdf
> >
> > "GPS and GEO satellites are threatened only by the very high yield (~ 10
> > Mt) detonations of our trial set."
> >
> > I'll note that the largest the US has detonated in space are the Teak
> > and Orange shots 3.8Mt (at <100km), and only Starfish Prime (1.4Mt) at
> > 400km cased significant problems.
> >
> > The usual "use case" for EMP is to affect aircraft and ground based
> > assets, and the burst height is low (so the air around the burst is
> > denser - more particle interactions = more current = more field) -
> > conversely, this reduces the flux at 20,000 km (where GPS is) and
> > 36,000km (GEO)
> >
> > Ultimately, it's that your victim is a Long, long ways away from
> > whatever the phenomenon is.
> >
> > I've been doing a lot of analysis on EMI/RFI effects on precision timing
> > in GEO+1000km - we are looking at bursts from the sun, and timing it
> > with GNSS satellites.  Things that I agonized over (high power shortwave
> > broadcasters radiating 500kW into a 24dBi curtain array) in my LEO
> > satellite at 500km just become a non-issue at 37,000 km.  Inverse square
> > law really helps.
> >
> >
> > Anyway, that DTIC report will give you plenty to geek out over.
> >
> >
> > Yes, there would be significant disruption in timing accuracy due to the
> > ionized particles - I'm not sure if dual frequency would be enough to
> > compensate.
> >
> >
> > I think alternate timing and nav systems are good idea, but selling it
> > as "GPS will be knocked out by EMP" isn't going to get you very far.
> >
> >
> > > Cheers;
> > >
> > > Tom Knox
> > >
> > > actast at hotmail.com
> > >
> > > "Peace is not the absence of violence, but the presence of Justice"
> Both
> > MLK and Albert Einstein
> > >
> > > ________________________________
> > > From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of paul
> > swed <paulswedb at gmail.com>
> > > Sent: Wednesday, August 5, 2020 11:21 AM
> > > To: Discussion of precise time and frequency measurement <
> > time-nuts at lists.febo.com>
> > > Subject: Re: [time-nuts] eLORAN will be on the air GRI 99600
> > >
> > > 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 <magnus at rubidium.se>
> > 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
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-- 
- Forrest