Conference unifix::sailing

    Go ahead. However, I have my SeaRanger ABS 2001 hooked up to a 12
    volt battery, rather than to a converter. 
    
    This particular loran has a simulation mode that lets me parctice
    using the different functions. Now that I am more familar with the
    unit, I use it at home to update, modify, or add new LAT/LONs. 
    
    Using the loran at home does make one more proficient when you get
    it on the boat.
    
    Good luck
    
    PS I don't think using a converter would damage the unit, however,
    I'm not and expert.
    
    Paul

    Don't do it without a battery in the circuit.  Some converters generate
    high peak voltages that may damage the power supply in the LORAN.
    Always use a battery in the circuit to provide a load to absorb and
    filter the high voltage spikes that a converter/charger might generate.

    One of those regulated 12V supplies (like the 13.8V Radio Shack
    1A regulated power supply) works fine.   The 3 terminal regulator 
    in these units is as stable as a battery and electrically quieter.
    
    I did what you are thinking about several years ago with my
    new RAYNAV 550.   Although the L/L and C/S didnt change much,
    it was fun to learn something about the unit without a lot
    of distractions.   I even thought about hooking it up in the
    car and driving around, but the ignition noise kept the unit from
    locking onto more than one slave.
    
    Have fun.
    
    Walt

Over in "Boating" I responded the potential Loran damage issue as follows.
Jerry

              <<< VICKI::SIE$DATA0:[NOTES$LIBRARY]BOATS.NOTE;1 >>>
                              -<   PowerBoats   >-
================================================================================
Note 251.5                       LORAN at Home                            5 of 5
CIMNET::CREASER "Auxiliary Coxswain"                 11 lines   1-FEB-1989 08:01
                         -< Rare but why risk damage >-
--------------------------------------------------------------------------------

    Re .4 That's why I said "WELL FILTERED". I assumed and should not
    have, that most people would know to power the Loran on and off
    after the power supply is already on and stabilized. DO NOT use the
    the supply's main switch to apply and remove power from the Loran.
    
    BTW many newer marine electronics devices are able to operate over
    much wider voltage ranges. 9-40 in becoming almost common place.
    This is a good item to check out when shopping.
    
    Jerry
    

    If your boat battery is readily available, use that.  Use any battery
    charger to periodically re-charge the battery, preferably in between
    loran "experimenting". Good luck, I have the Apelco 6600 and might
    do a little "refresher" before the season starts.
    

The attempt was overwhelmingly successful.

I followed the best of the advice given, bought a high quality regulated 
13.8vDC power supply and powered up my RAYNAV 570 this weekend.

The antenna was a bit of a problem. Discovered that the more vertical its 
orientation the better.  Only made a few dB of difference as to whether the 
antenna was in the house or out on the deck in the back.  

I strongly recommend this capability to anyone new at using a loran.  I am 
confident that I saved myself a good number of "training" hours on the 
water.  I was able to load waypoints and connect them into potential trips.

In fact, it almost felt like I toured Nantucket Sound, fished the Middle 
Ground, visited Cuttyhunk and Block Island this weekend.  

I can also see that having the capability to operate the loran at home can 
allow one to prepare for a cruise without utilizing valuable boating time.

Carl

    I just bought the highly-rated Apelco DXL6300 at the boat show ($239 at
    the Bliss booth - this is an amazing price).   Set it up on the kitchen
    table to practice (using 2 6V lantern batteries).  Got good signal
    strength with just a longwire antenna strung through the cupboard
    handles.
    
    It comes up normally and all functions work accoding to the book,
    except that if I turn it off and then back on again, the Lat/Lon
    displayed for current position is always different, varying by up to a
    minute in both directions.  The displayed value stays very stable, with
    just some occasional bouncing of the hundredths of a minute digit, it's
    just not the same stable value as the last time the set was turned on!
    
    Is this related to home use?  Is it normal?  Is the unit bad?
    

    I have the same unit. I installed it on my boat last season and it
    worked flawlessly all summer. I also set up my unit at home just to try
    it out (gotta do something to get you through the winter). When I ran
    mine at home, I used a ground (water pipe, etc.) as well as the
    antenna. I found that the signal strength was weak on at least one of
    the three stations. Is the warning display on for any of the
    functions? The unit will signal you if it is having difficulty locking
    on the correct pulse. You can put the unit into a mode where it will
    display the signal strength of each of the three stations selected.
    Are you using the same two secondaries each time? Selection of
    different secondaries will yield a slightly different Lat Lon.
    Also, are you picking secondaries whose lines cross at a large angle on
    a chart? Ideally, the loran lines selected will cross as close as
    possible to 90 deg. 
    Most likely, your unit is operating correctly and you just need a
    little more familiarization with it. I think you will be more than
    satisfied with its performance.
    
    John

    I'm letting it pick the secondaries.  It always picks 1 and 2 on the
    9960 gri chain.  I live on a hill in Arlington - the signal strength
    readout was 50 or above on all three stations.   No signal quality
    indicators went on.  I didn't ground the unit at all, presuming that if
    the signal strength was high I didn't need to (or do I).   Running a
    wire to the sink is easy enough.
    
    Assuming your boat is always at the same place when you turn the unit
    on (home slip or mooring), what do you typically see for LL differences
    from time to time.

    Re: .9
    I don't typically use Lat Lon when I navigate with the Loran. Also, I
    don't recall the power-up to power-up repeatability. What I can tell
    you is that when I use the Loran to navigate to a certain bouy, for
    example, by storing a TD waypoint, it will bring me back to that
    position to within a few boat lengths.
    
    John

>it will bring me back to that
>position to within a few boat lengths.

Impressive, since bouies move, by at least a few boat lengths, this is
exactly the same place for all intents and purposes.  As one who's considering
a Loran purchase, what brand and model do you own?

F.

    re: .11
    	It's an APELCO (designed by Ratheon, the ones who did the Patriot
    missle). When I said within a few boat lengths, I didn't say what size
    boat. ;-)
    
    

    I own a Ray-Jeff 9900 and slip my boat in Galveston Texas. I experience
    similiar startup anomolies on lat/lon. Typically, on lat/lon I show my
    boat to be about 1-2 miles inland from where I am. On TD it's much
    closer. Near my slip is a large  set of VERY high voltage lines.
    
    Once on the water, my lat/lon is still off enough to only navigate by
    TD's, but like the previous responce, I have repeatability to offshore
    bouys and oil rigs to within 200'.
    
    Robert

    On most lorans you can adjust the error that is caused by the
    transmission distance over land to your set.  The reception is affected
    by the speed the transmission travels over land vs. water.  On my
    Micrologic Explorer you can enter a known position from a chart.  This
    will differ from what your loran is saying.  Once you enter the correct
    lat/lon it will calculate the offset and apply it to your location. 
    This offset will correct any error for a area close to where you made
    the correction.  If you travel some distance (how far I don't know) you
    would need to re-enter a correction factor as the land/water distance
    ratio would be significantly different.  You can relate this to compass
    differences from location although it is not a magnetic issue with a
    loran.
    
    Check your owners manual on how to make this adjustment.
    
    Chuck

    Well the problem is solved.   I now get consistent LL values within a
    couple of hundredths of a second each time the unit comes on.
    
    Turns out I there is an undocumented feature on the unit - it
    apparently takes it some time to calculate LL from TDs (I guess the
    math is pretty hairy with all those hyperbolic functions).   While it
    is grinding away doing this, it blinks the decimal points in the LL
    readouts to tell you it's not done.   The instruction manual says
    nothing about this, but apparently many Apelco/Raytheon units do this.
    
    So when it says "Ready" on the startup sequence, it means ready with
    TDs, LLs to follow in a bit.  And don't believe the LL until the
    decimal point stops blinking.
    
    BTW the Jan issue of powerboat (sorry) reports says they love their
    Apelco 6300 (thus agreeing with practical sailor), but swear at the
    instruction manual every time they try to get some information out of
    it.   So far I'd have to say I agree.

    I wouldn't worry too much about navigating with Lat Lon. We find that
    we always use TDs when using our Loran. Even when we are forced to use
    Lat Lon, we always capture the actual position when we reach the
    waypoint. I purchased a cruising guide last year from Embassy. The
    guide is great. It covers all of the harbors from Block I. R.I. to
    Marblehead. In it, most of the key bouys are labeled with Loran TDs.
    The TDs are actual (observed) positions. In other words, they went
    there in a boat and recorded the reading on their on board LORAN unit.
    There is also a table in the back of the book listing observed TDs for
    all of the rest of the aids to nav. for those waters. I have found them
    to be VERY accurate. The loran operates in TDs and then has to do an
    approximation of Lat Lon. So, why use Lat Lon unlesss it is absolutely
    necessary?
    
    John

re .15:

Actually, the math is simple, I think. What is not simple is accurately 
determining the TDs from weak loran signals buried in noise. This takes 
some time.

My loran, admittedly an older design, only displays TDs to the nearest 
0.1 microsecond. Even sitting on a table, the displayed TDs jump around 
by plus/minus 0.2 microsecond several times a minute. How stable are the 
TDs displayed on your Apelco? Is the display always (for example) 
44000.00 or is there some variation or change even with the loran 
sitting still? 

I would suspect that there is a tradeoff between the time used to 
determine the TDs and the stability of the displayed TDs. That is, 
to process the signal sufficiently to get a TD accurate to 0.01 
microsecond might take significantly longer than only determining the 
TDs to 0.1 microsecond.

Loran signals travel at roughly 10 feet in 0.01 microsecond. At six 
knots your boat is moving about 10 feet per second. Depending on signal 
processing speed, this may result in some error in the TDs. Does the 
manual for your loran discuss this at all? (The manual for my TI says 
something to the effect that the TDs are only usable for speeds less 
than 250 knots or so). Since it is very hard to plot a TD to the nearest 
microsecond, I don't see any particular value in displaying TDs to 0.01 
microsecond. Moreover, displaying TDs to the nearest 0.01 microsecond 
likely will make you feel that the loran is more accurate than it really
is. I've measured the TDs of several bouys several times over several
years. The mesurements have differed by as much as 1.5 microseconds both 
larger and smaller, yet my loran says its internal timebase has drifted
only slightly and consistently in one direction. Hmmmmm. 

Alan

    These are all good questions.  The manual gives little insight.  No
    wonder they get big bugs for loran instructional videos.
    
    As a novice, some of the questions I've already come up with...
    
    1) On the Maine coast I can get both the 9960 and 5930 chains
    pretty well.  The 9960 signals are stronger but the 5930 gives me
    LL readings almost dead on with no correction other than ASF. Which
    should I use?   9960 shows my mooring as being about a mile away from
    where it is (isn't this an awful lot of error?)
    (The !@#$%^ manual does say it's normal to enter LL corrections to get
    the unit to agree with the charts, but how much is normal?  I thought
    asf-corrected readings were supposed to be within 1/4 mile).
    
    2) I get S/N numbers of 85 or better with only the lower half of the 8'
    antenna connected.  Is there any reason I shouldn't just stow the upper
    half until such point as I need it?  Or are there factors other than
    the signal/noise numbers?
    
    3) I hear (again, not stated in the manual) that you should pick
    secondaries whose gradients cross as close to 90 deg as possible.
    This I actually understand, but is this higher or lower priority than
    picking secondaries with strong signals?

re .18:

re automatic ASF (this is, as I recall, discussed in other loran notes):

Automatic ASF corrections have to be based on a fairly coarse model of 
the world (memory limitations in the loran). Therefore, they cannot 
account for small area anomalies. I suspect the automatic correction is
fairly good some distance from land. I have noticed some quite large
changes over a small distance in the corrections needed to get the right
lat/long (eg, at the entrance to Winter Harbor in Maine). If my loran
had automatic ASF correction (it doesn't) I probably wouldn't use it for
this reason. Your experience with the 9960 chain and your mooring
doesn't surprise me at all. The only time we use lat/long is when the
chart doesn't have the TD lines. 

I would use whatever chain gave the best signal to noise ratios. Unless 
the gradient crossing angle gets down to 30 degrees or so I wouldn't 
worry. Finding the signal peak with a weak(er) signal will (my guess) 
give a bigger error.

    I was under the impression that the TD lines on a chart would only
    apply to one specific loran chain.  So if you use TD's the chart should
    specify the chain.  I use lat/lon so it has never been a problem.
    
    Chuck

re .20:

Some charts do in fact have the TD lines for two loran chains -- in the
northeast US both the 9960 and 5930 lines are on some small scale 
charts. Finding the right line(s) to plot a position can be difficult at 
night on a bumpy ocean. 

re .17:

I recently reread the Practical Sailor review of inexpensive lorans. The 
review mentioned that the error in the position given by the lorans 
decreased when the loran (boat) stopped moving. This does imply that the
data averaging algorithms do require some computing time (several
minutes perhaps) to give the best possible results. 

This brings to mind another question -- many lorans have an anchor watch
that is supposed to sound an alarm if your anchor drags. Hmmmm, if
several minutes of data analysis/averaging are required to determine
your position accurately, it might well be that the loran will require
several minutes to determine if your anchor has dragged, in which time 
you could be unexpectedly ashore. Has anyone done any experimenting with 
this feature to determine its usefulness?

    It's basically useless.  You set a radius to allow you to swing 
    (say .03 nm)  Now, the combination of atmospheric conditions and
    local interference (the guy downwind in the Uniflite running his
    blender) mean that ANY loran won't be that accurate so it beeps you
    awake every 20 minutes.  So after a few times of jumping out of your
    bunk, finding your glasses, running topside barefoot in your underwear
    (or less), slipping on a dew-wet deck, and slamming your toes into the
    whisker pole chock . . . you decide to set the anchor watch to .5nm
    so you can get some sleep.  Next night you decide that an anchor watch
    is about as useless as 200 waypoints.
    
    Maybe GPS will have a workable anchor watch feature.
    
    Adam

��    I just bought the highly-rated Apelco DXL6300 at the boat show ($239 at
��    the Bliss booth - this is an amazing price).   Set it up on the kitchen

    I managed to find this at the Miami show for $224.10. 
    Suprisingly, most dealers were trying to sell it for
    $269.  As some supermarket chain says: 'Why pay more?'

    	- Lee

re .23:

Ah ha! You've confirmed my suspicions and affirmed my belief that the 
best way to get a good night's sleep is to use a big anchor with a lot 
of scope. 

re .22 & .23

I used to have a Sea Ranger loran and it was worthless for anchor 
watch. It drifted and was sensitive to noise from fluorescent 
lights, generators and on and on. I trash canned the thing 
in the 3rd season of use after I almost sailed onto a beach at 
night, in fog because the Ranger gave WRONG TD's and LAT/LONG just 
when I needed it the most.

Last year I bought a Raytheon RayNav 570 and there is a 
significant difference in total performance. I have used the RayNav 
for anchor watch without problems but not often enough to stake 
claims that it is completely free of false alarms. It seems to
have better immunity to noise than the Sea Ranger but it also 
is bothered by a local fluorescent light.

In general, I wouldn't put much hope on a loran to allow 
undisturbed sleep when they are used for anchor watch. Better to 
use a good anchor with proper scope and chain.

Joe

    Anchor watch appears to be useless just from reading the instructions.
    The smallest allowable drift you can set is .01 NM - approx equivalent
    to .01 minutes of lat/long, but the .01 min digit on the L/L display
    is constantly bouncing around up or down a couple of hundredths just
    while standing still.  A look at the course/speed display will confirm
    that zero motion is a figment in the imagination of the Loran. 
    Something like .1 NM is probably the smallest watch radius that will
    eliminate most false alarms, but now we're talking 600 ft!  So much
    for anchoring in a cozy harbor...

    Well, since I'm home and thinking about Loran I decided to put the
    question in this topic :-)
    
    Does anyone have any experiance or knowledge of the effectivness of
    portable (handheld) loran units that are being offered??  Like handheld
    VHF's I imagine there are some tradeoffs, but the concept sure
    is attractive. 

    I have a Ray-Jeff Pl99.  
    
    I would not buy another one ..... I'd build it in.

    The biggest problem with a hand held, to my view, is the problem of
    sync up time- it takes several minutes for them to lock in, so its
    likely you will wnat to leave it on for most of the time. That causes a
    battery life problem, so you wind up with a wire to it. Then you find
    the sensitivity of the portable ant is to low, so you hook up a real
    ant. At that point any possible benefit of handheld is long lost. I
    went for a small fixed unit, even tough I use it on a basically open
    boat.

    Thanks for the comments.  They point in the direction I expected; 
    
                             Tom