NavList:

Bill wrote:


> The crew decided to crank it up, mostly out of curiosity I suppose, and it
> was 10' off on both lat and lon.  We grabbed the manual and went about
> setting it up from scratch.  I read, my buddy tweaked.  Fired it up and same
> results.  So my buddy read and I tweaked.  Same results.  My guess, some
> sort of antenna problem (short, open).

It's maybe too late to know this, but I'd be curious about a couple of
things:

1)  How old was the Loran?

2)  Were the readings consistently off by always a certain amount, or
were they randomly off?


The reasons for these questions is that they remind me of my first
Loran, purchased in the early 1980s.    It was a Furuno unit.  I'm an
electrical engineer, and the insides of the box were truly magnificently
constructed.  Proverbial brick outhouse.   I think the base price of the
unit was around $1200, but I paid an extra $500 to get the "upgrade" to
have it display latitude and longitude rather than TDs.

After I installed it I discovered the L/Lo readings were off by about
1/4 mile.   After learning the fine grain details of the workings of
Loran many years later (and, by the way, the US Government's Loran User
Handbook is way better than the GPS handbook in explaining the
technology to someone who is technically knowledgeable), I guess that
the unit didn't correct for ASF (variation in the speed of radio
propagation as the signal travels over land or water).

The good news, though, was that the unit was CONSISTENTLY off.  If it's
longitude readout was off by 0.25 minutes at a known location, the
readout would be off by the same amount at all nearby locations.

Well, all I had to do is treat this like IE on a sextant.  If I wanted
to get to a new waypoint, all I had to do is measure its L/Lo and then
adjust the numbers for the loran's "offness" before entering them as
waypoints.

I successfully used this beast navigating in thick Maine fogs for many
years, always hitting desired points within 50 feet or so.

The poor Furuno died after a dozen years (just before GPS became
popular) and I replaced it with a Micrologic unit (speaking of the
dead).  It was 1/10 the size of the Furuno, had many more functions, and
L/Lo readings accurate to 0.01 of a degree (at least on the East Coast
of the US where the crossing angles are better).

But I missed the challenge of the old Furuno.  Maybe I shouldn't
castigate George for his old-fashioned ways so badly....

Lu Abel

PS - A "sea story" about the Furuno:  The very first time I ever used it
in a truly dense fog was in Maine.  We woke up one morning and could
barely see the bow pulpit on my 36' sloop.  We felt our way out of the
harbor and I entered a buoy about 2 miles away as our first waypoint
(using, of course, the offsetting technique described above).  I
determined our compass course and set the Loran to read cross-track
error and distance to go.   The distance to go display read in tenths of
a mile.  One of my crew was steering while I figured out our next
waypoint.  He suddenly cried out "Lu, the distance to go just dropped to
zero and I don't see the buoy."  I instantly replied "Jim, don't worry,
that just means we're within 500 feet of the buoy, hold course!"   Sure
enough, a few minutes later the buoy popped out of the fog almost
directly on our bow.  To this day I don't know what caused me to figure
out that the distance to go display was truncating numbers and to say
what I said (there was most certainly no conscious thought about it on
my part).

--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---