-> I had never thought of diferrentials as to one loran to the other.
-> Most people tell me you get about fifty ft to fifty yards within the
-> area you are using. However one boat I go on, which I credit
-> experience, puts us on the spot everytime within spitin distance.
That's repeatability for you.  Mine will pretty much put you in the same
spot over and over again, but not find the spot you have the coordinates
for at all.  There's considerable variation from unit to unit.  Lorans
are measuring the difference in the timing of radio signals from
different towers, a master and two slave towers.  Since it's known
exactly how far apart the signals are initiated, the difference is due
to distance and, as you note, atmospheric conditions.  If there's a
serious electrical storm in the area, accuracy does deteriorate, but
most of us are headed home before that happens.
-> This leads back to accuracy of the machine. There must be a
-> calibration of some sort on this type of equipment.  And as
-> with other radio signals I would imagine atmosphere may play a
-> role in deviation.
It does from trip to trip, but this isn't the cause between two units on
the same trip.  Each will read a bit differently.  Time differences,
known as TD's, are so minute that it's pretty tricky to tune a Loran and
about impossible to tune two the same.  Most, however, have a user
accesable adjustment to match a known unit.  My charts show both
Lat/Lon and TD's for the whilstle buoy at the sea entrance to Port
Everglades (Ft. Lauderdale).  My loran is set to match that
location which, whether right or not, is always quite close to the
same.  The only time I vary from this is when I am looking for
wrecks based on someone's dive book.  Under these circumstances, I
look for a site in the book which I have visited and recorded.
That gives me what my unit will read and the book gives me theirs.
Having two sets of coordinates for the same place gives me the
correct adjustment for finding sites in the same book (assumes same
Loran) I have not visited before.  It works.
-> Well the gulf diving out of Clearwater at depths of fifty feet have
-> pretty good vis and water temp is great. The reefs are holding fish
-> and tropicals seem to be plentiful.
You have reefs?  Oh, you mean those little ledges you find here and
there if you're lucky :^).  Here on the SE coast, we have REEFS!!
-> Weather permiting not bad conditions, early morning to early
-> afternoon provides best vis as pariculates do start to affect in the
-> afternoon.
That we have in common.  The winds whip up here in the afternoon too.
Lately, we have major thunder storms every afternoon.  It's that time of
year.  Acutally, I get a kick out of this weather.  I have lots of
friends who came here over the last 5-10 years.  During most of that
time, we've had unusually dry summers and that's what they got used to.
Now that more normal summer patterns are here, all the newbies to the
area a complianing about the lousy weather.  It's a hoot to tell them
that this is the norm, the "good" weather they expect is the exception.
Lee
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