Re: Comparing phase of physically distant signals

From	Don Y <this@isnotme.com>
Newsgroups	comp.arch.embedded, sci.electronics.design, comp.realtime
Subject	Re: Comparing phase of physically distant signals
Date	2013-08-03 12:34 -0700
Organization	Aioe.org NNTP Server
Message-ID	<ktjlvj$u15$1@speranza.aioe.org> (permalink)
References	<kticf7$hg3$1@speranza.aioe.org> <51fd247c$0$64328$c3e8da3$5e5e430d@news.astraweb.com> <b64rj8Fd0uiU1@mid.individual.net> <ktjdc5$snt$1@dont-email.me>

Cross-posted to 3 groups.

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Hi John,

On 8/3/2013 10:13 AM, John S wrote:

>> Don hasn't given us any specs yet but if this has to be in the
>> sub-microsecond class then real terrestrial RF may be needed. Even old
>> Loran could do that back in the 80's, over lots of miles:
>>
>> http://tycho.usno.navy.mil/ptti/1988/Vol%2020_13.pdf
>
> According to the paper you referenced, it was not sub-microsecond.
>
> Also, it discusses only the surface wave. Reflections may occur at other
> frequencies and upset the path length.

TD's ("LORAN coordinates") are expressed in tenths of microseconds.
Anything worse starts to get impractical (100ns is NO BETTER
than ~50 ft -- and can easily be much worse as the geometry of
the coordinate "basis" varies depending on where you are
located wrt the master and secondaries you are currently using).

You track the LORAN signal (a "pulse" modulated 100KHz?) by
watching the position of the 3rd (?) zero crossing of the carrier
(you also monitor this on the first of the pulses in the
CODED pulse train) so you can avoid/minimize multipath effects.
Most receivers also allow you to move to *another* zero crossing
(i.e., +1 or -1) if the 3rd is in the noise, etc. (though this
affects the absolute time differences cuz you are now operating
on the next 100KHz cycle)

[Sorry, it's been more than 35 years since I've worked with LORAN
so many details are fuzzy]

There are variations in the propagation delay "over land" and
"over water" so the theoretical math needs to be tweeked a bit
if you want to map a TD pair to (lat,lon) -- but there are
also variations in the shape of the Earth (oblateness) that
have to be accommodated.

Regardless, in a given region of the ocean (where most commonly
used) things are relatively repeatable, day to day.  E.g., you
could set a lobster pot, record the TD's, return to those TD's
some time later and be able to see it from the vessel (there's
more variation in where a buoy would appear on the surface
due to tides/currents and the fact that a tethered buoy isn't
"directly above" whatever it is tethered to!)

Given that it predated (commercial) GPS by decades, it was
amazingly useful!

Thread

Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 00:45 -0700
  Re: Comparing phase of physically distant signals Jan Panteltje <pNaonStpealmtje@yahoo.com> - 2013-08-03 07:51 +0000
  Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 09:58 +0100
    Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 13:21 +0300
      Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 12:16 +0100
      Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 11:56 -0700
        Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:17 +0100
          Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 13:41 -0700
            Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 22:46 +0100
              Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 14:57 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 23:09 +0100
    Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 13:58 +0300
      Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 12:30 +0100
    Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 16:08 +0300
      Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 14:22 +0100
        Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 16:38 +0300
          Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 10:46 -0700
      Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 10:40 -0700
        Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:04 +0100
        Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-04 15:55 +0200
          Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-04 19:42 +0300
            Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-04 21:08 +0200
              Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-05 15:28 +0300
                Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-05 22:17 +0200
                Re: Comparing phase of physically distant signals Richard Damon <Richard@Damon-Family.org> - 2013-08-05 23:20 -0400
    Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 14:26 +0100
    Re: Comparing phase of physically distant signals George Neuner <gneuner2@comcast.net> - 2013-08-03 14:47 -0400
  Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 08:17 -0700
    Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:08 -0700
      Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:37 +0100
        Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:57 -0700
          Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-04 15:58 +0200
      Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 12:44 -0700
        Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 18:36 -0700
          Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-04 09:56 -0700
            Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-05 14:53 -0700
              Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-05 15:38 -0700
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 01:25 -0700
                Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-07 08:06 -0700
                Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-07 09:21 -0700
  Re: Comparing phase of physically distant signals josephkk <joseph_barrett@sbcglobal.net> - 2013-08-03 15:40 +0000
    Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 10:05 -0700
      Re: Comparing phase of physically distant signals John S <Sophi.2@invalid.org> - 2013-08-03 12:13 -0500
        Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 10:26 -0700
          Re: Comparing phase of physically distant signals John S <Sophi.2@invalid.org> - 2013-08-03 12:51 -0500
            Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 11:54 -0700
              Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:27 +0100
                Re: Comparing phase of physically distant signals George Neuner <gneuner2@comcast.net> - 2013-08-05 03:26 -0400
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-05 10:34 +0100
                Re: Comparing phase of physically distant signals Richard Damon <Richard@Damon-Family.org> - 2013-08-05 23:29 -0400
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 08:53 +0100
          Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:49 -0700
        Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:34 -0700
      Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:18 -0700
        Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 12:52 -0700
          Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 13:21 -0700
            Re: Comparing phase of physically distant signals Jeff Liebermann <jeffl@cruzio.com> - 2013-08-03 13:31 -0700
              Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 14:46 -0700
                Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 15:03 -0700
                Re: Comparing phase of physically distant signals Jeff Liebermann <jeffl@cruzio.com> - 2013-08-03 17:25 -0700
            Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 14:50 -0700
    Re: Comparing phase of physically distant signals "Paul E. Bennett" <Paul_E.Bennett@topmail.co.uk> - 2013-08-04 11:06 +0100
      Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-04 12:19 -0700
  Re: Comparing phase of physically distant signals John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> - 2013-08-03 11:47 -0700
  Re: Comparing phase of physically distant signals Richard Damon <Richard@Damon-Family.org> - 2013-08-03 18:23 -0400
  Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-05 16:53 +0100
    Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-05 13:19 -0700
      Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 00:27 +0100
        Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-05 20:09 -0700
          Re: Comparing phase of physically distant signals Paul Rubin <no.email@nospam.invalid> - 2013-08-05 22:12 -0700
            Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 09:12 +0100
            Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 01:47 -0700
              Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 10:08 +0100
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:25 -0700
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:48 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 10:49 +0100
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 03:06 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 11:57 +0100
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 10:28 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 21:52 +0100
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 01:34 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-07 09:46 +0100
              Re: Comparing phase of physically distant signals Les Cargill <lcargill99@comcast.com> - 2013-08-06 07:22 -0500
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 10:42 -0700
                Re: Comparing phase of physically distant signals Les Cargill <lcargill99@comcast.com> - 2013-08-06 23:04 -0500
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 23:50 -0700
                Re: Comparing phase of physically distant signals Les Cargill <lcargill99@comcast.com> - 2013-08-07 13:05 -0500
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 18:22 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-08 09:35 +0100
              Re: Comparing phase of physically distant signals Paul Rubin <no.email@nospam.invalid> - 2013-08-06 22:18 -0700
                Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 03:09 -0700
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-07 12:39 +0100
                Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-07 13:18 +0100
          Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 09:23 +0100
            Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:02 -0700
          Re: Comparing phase of physically distant signals "Paul E. Bennett" <Paul_E.Bennett@topmail.co.uk> - 2013-08-06 09:49 +0100
            Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:17 -0700
  Re: Comparing phase of physically distant signals Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-08-16 21:07 +0100
    Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-16 14:50 -0700
      Re: Comparing phase of physically distant signals Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-08-18 19:55 +0100
        Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-19 11:43 -0700
          Re: Comparing phase of physically distant signals Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-08-20 21:43 +0100
            Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-20 14:49 -0700

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