Conference unifix::sailing

    With the prices of LORANS getting to a reasonable range you will
    see their use increase, I'm sure.  Their usefulness is severely
    limited when close to land, however, due to reflections and
    disturbances created by the land mass.
    
    RDF will continue to be the choice for finding a inlet or winding
    your way from bouy to bouy in the fog.  I carry a back-up RDF for
    my LORAN and a portable AM radio as a backup for my RDF.  The AM
    radio was the only way I found Bermuda on my last trip due to 
    battery failure.

    Your concern for the future will be the GPS (Global Positioning
    System) satellites being installed.  They are projecting full operation
    for the military by the year 2000 and private use shortly thereafter.
    
    This will probably make all current modes of electronic navigation
    obsolete.  I still beleive there will be a place for RDF and your
    sextant, so don't throw away either.
    
    Happy Sailing,
    Jeff
    
    
    

    I have a $4.95 Radio Shack AM radio that a lot of land lubbers must
    hate, but I love.  It is so directional (internal loopstick), that
    prior to the Loran, I used it and a hand bearing compass with great
    accuracy during those hazy days crossing LI Sound (no visable land).
    
    Along the New England coast, at least Boston to NYC, it offers more
    variety than radio beacons, so I could always get more than 2 bearings,
    if I wanted (often as not I would cross depth, DR and 1 Radio bearing
    LOP for a fix, since I could do all at once).  Besides, it give
    you a chance to hear how unbearably hot it is ashore.
    
    Walt

Sorry, I disagree with the above. Sure, loran can be inaccurate near a 
coast or up a bay, but it is still more accurate and far easier to use 
than a RDF. 

RDF problems:

1. Few marine beacons. AM broadcast stations are better than nothing but 
are still inaccurate.

2. The directional null of even a good RDF tuned to a marine beacon is 
some 2 to 5 degrees. Try plotting a line of position with a 5 degree 
uncertainty and you'll quickly see how uncertain your position can be.
The worst error I've seen with my loran was under a mile. With a 5 
degree null, your position is uncertain by more than a mile if you're 
more then 11 miles from the beacon. 

3. RDFs have deviation, just like a compass. I made a deviation table 
for my RDF using the Boston LNB. The deviation curve is roughly a sine 
curve and the maximum deviation (RDF on the chart table) is around 18 
degrees (!). I've verified this using other beacons. 

4. Getting a good RDF fix in rough weather is virtually impossible (the 
boat's heading is too unstable). 

Granted, homing on a beacon works quite well. We bought our RDF back in
the dark ages when lorans were very expensive and used it to find
Southwest Harbor in a pea soup fog after an offshore passage from
Marblehead. We haven't used it since buying a loran. In those parts of 
the world lacking loran coverage, an RDF would still be useful (assuming 
that the natives have kept the beacons beckoning). 

Alan

    I guess I,m going to side with the el-cheapo RDFers on this one.
    If you are comparing a "full size, full function, full price" RDF
    at $275 with a $600 Loran, it seems like a waste of money for the
    RDF.  But I've used a $70 portable RDF with earphones (forgot the
    name) that was a just fine.  Even people who can't pop for a Loran,
    can shuck out 70 bucks for use on the occasonal longer trip where
    they feel they need some help on their DR.
    
    I'm curious about Jim's microprocessor controlled RDF (ADF?) that gets
    accuracy of a few hundred yards.  Could this be had for under $100
    and run off of batteries?  That would be a usefull and sellable
    item.
    
    	Travis

    As one with a somewhat personal (RDF::RDF) stake in this, I'd like
    to first point out that..
    
    "The rumors of my demise have been greatly exaggerated"
    
    Contrary to the title of the base note, I am still breathing, still
    kicking, and hope to do so for quite some time.
    
    
    
    Second, I agree with the recommendation for sticking to a low-tech,
    low-budget setup.  I just don't see that much more accuracy coming out 
    of buying a "real" RDF (at least for coastal cruising) over a "Time
    magazine giveaway radio", at least not without getting into LORAN
    price ranges.
                                   
    Many LORANS will get you back to a place you've been before within
    50ft.  Consistency of error can sometimes be important.  With an RDF
    you have no such guarantee.

    A cheap and directional AM radio sounds like a good idea as a backup.
     
    Rick

    Walt,
    
    I also have a little AM set, IR�9.95 (!) which was, dare I say it,
    made in an Eastern bloc country, the ONLY one I have ever seen at
    the price, which included enough space on the LW dial to include the 
    "beacon band" of 290-340 KHz (approx). Great "yoke" as we say here,
    I'll dig out the details if you want.
    Jim

    Travis,
    
    Oh dear. I guess it will have to remain a toy. Or a most, a specialty
    for RDF enthusiasts. The internals of the thing will make it cost
    around IR�250 just to produce, at local rates. Otherwise, it would
    need to sport dozens of software nav goodies, none of which I have
    even dreamed about. Yet!
              -Jim