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    Re: LORAN-C to be shut down.
    From: Lu Abel
    Date: 2009 Dec 06, 16:53 -0800
    Good point, Irv.   I've been navigating since navigation texts included a chapter on RDF.  Almost invariably they mentioned that there was danger in using commercial AM stations for RDF -- antennas often inland, sometimes mismarked on charts or other publications, etc.   Advice was generally to stick to CG RDF beacons -- low frequencies assured groundwave (vs skywave) propagation, locations accurately marked on charts and available in the Light List, etc.    I even remember when Bowditch had a table for compensation for great-circle propagation of signals from distant transmitters (ie, you got a direction to the transmitter, but it was the initial direction of a great circle which all of us expert navigators know (right?) is not the rhumb line bearing to the destination.

    Lu

    Irv Haworth wrote:

    Might I also add that the towers associated with civilian radio stations are generally inland. This may (depending upon bearing taken) be several degrees off due to refraction.

    As an aside and depending upon radio used (freq./mode  etc.) one is also able to use antennae associated with airports. Needless to say to use these on needs either  an air map or get φ & λ from google .

    VE7CVL

     

    From: Lu Abel [mailto:lunav@abelhome.net]
    Sent: Saturday, December 05, 2009 5:58 PM
    To: navlist@fer3.com
    Subject: Re: [NavList 10950] Re: LORAN-C to be shut down.

     

    Why build your own??   Many cheap AM receivers use a loop antenna which is fairly directional.

    I also wonder what benefit one gets (other than "yes, it can be done" satisfaction) of creating a RDF with 3 degree accuracy.   Each degree of bearing inaccuracy gives 100' of inaccuracy per nautical mile of distance from the station.   Shoot a station from 10 nm offshore with your proposed RDF and you have a 1 nm inaccuracy in your LOP!

    Apache Runner wrote:

    Although this is a completely out-of-the-box idea, I've been working on an AM radio receiver/direction finder for fun.    The FCC publishes the lat/long for all stations in the US.   

    I haven't seen a variable capacitor in ages, but managed to find some beauties online, and am making my own antenna.    Right now, I think I can get an accuracy of maybe 3 degrees, but that's just a guess.  

    I'll post something when I have it up and running.

    On Sat, Dec 5, 2009 at 3:03 AM, glapook@pacbell.net <glapook@pacbell.net> wrote:

    I know we have some commercial air pilots on the list and was
    wondering if
    they thought an aircraft RDF unit could be easily mounted on a boat.
    The
    aircraft industry seems to be the only ones making small units these
    days.
    I might go ocean cruising with a friend who is presently re-fitting
    his
    boat, and I am a big fan of redundancy, and thought this might be a
    workable
    solution.

    ---------------------------------------------------------------------------


    An ADF will work on a boat but they aren't cheap, the readout is only
    marked every 5 degrees and the antenna has to be mounted somewhere. If
    you want RDF capability just by an inexpensive digitally tuned
    portable radio that covers the LF band such as the Grundig G5 which
    also covers HF and has SSB capability so you can get your time
    signals  too. These all have ferrite rod internal antennas which are
    highly directional. Get one and tune a distant station. Then orient
    the radio in different attitudes and rotate the radio until you get a
    null which will let you know the orientation of the ferrite rod. Then
    you can use the edge of the radio to indicate the direction to the
    station. Place it on top of a universal plotting sheet to use as a
    compass rose placed on a table or nav station desk and rotate the
    radio to get a null. You may want to make a calibration table for it.
    Don't worry about the lack of a sense antenna which are really only
    needed by an ADF since a human can easily determine which is the
    correct bearing, the 180 degree ambiguity, which is a big problem for
    an ADF, is not a problem for a human.

    gl


    On Dec 4, 11:48 am, Bruce Hamilton <brucerhamil...@gmail.com> wrote:
    > If GPS goes dark, Jeremy will be in a great position to negotiate a salary
    > raise.
    >
    >  I had great hope for e-loran as going to a single system with no redundancy
    > seems risky at best. Even when Loran C coverage was poor, even the
    > information from a single chain would give you something to work with. In
    > the middle of Lake Superior, coverage was always spotty, and on the East
    > Coast of Canada we would often be on a single chain only 50 miles off the
    > coast.
    >
    > Jeremy, do you still have a working RDF?  I used them on aircraft all the
    > time, but must admit the one on the first ship I was on was not often used
    > and this was pre-gps. I have a working portable (Ray Jefferson) RDF that I
    > am going to try in a friend's boat. It is a pity that the technology got
    > left behind in the GPS age as the modern RDF's are apparently very good and
    > very quick. The signal from the multiple antennas is instantly processed and
    > you get an bearing read out.  The Canadian Coast Guard use them to get
    > instant fixes from distress signals in pre-GMDSS days. They have remote
    > stations they use to get a cross bearings from. No GPS required.
    >
    > I know we have some commercial air pilots on the list and was wondering if
    > they thought an aircraft RDF unit could be easily mounted on a boat. The
    > aircraft industry seems to be the only ones making small units these days.
    > I might go ocean cruising with a friend who is presently re-fitting his
    > boat, and I am a big fan of redundancy, and thought this might be a workable
    > solution.
    >
    > A fine page of old RDF units <http://www.angelfire.com/space/proto57/rdf.html>
    >

    > On Fri, Dec 4, 2009 at 8:09 AM, <Anabasi...@aol.com> wrote:
    > >  I read the following on a maritime forum site.  Looks like LORAN-C
    > > systems run by the US will be shut down sooner than we thought.
    > > -----------------------------
    > > The US Coast Guard released an internal message advising of the imminent
    > > termination of the long range aid to navigation Loran-C. Current plans call
    > > for the termination process to commence on 4 January 2010. The process is

    > > expected to take several months. ALCOAST 675/09<http://www.uscg.mil/announcements/alcoast/675-09_alcoast.txt>(11/25/09).

    > > *Note: This will mark the end of an era that started during World War II.
    > > The Loran system has improved greatly over the years and was on the edge of
    > > yet another advance: to enhanced Loran (eLoran). It is unclear how other
    > > nations, which operate their own independent Loran-C systems, will react to
    > > this development. *

    > > Courtesy: Bryantʼs Maritime Blog – 1 December 2009<http://bryantsmaritimeblog.blogspot.com/2009/12/bryants-maritime-blog...>

    > > ------------------------------
    >
    > > Not that this will affect many large ships.  My ship hasn't had LORAN
    > > capabilities since the antenna broke 3 years ago and the captain was too
    > > afraid to order a new antenna.  Most merchant ships are utterly dependent on
    > > GPS at this point, and would have a tough time remembering how to use the
    > > sextant if it came down to that point.  It will only get worse when the
    > > younger generations take command, having never known a time without GPS.
    >
    > > JCA
    >
    > > --
    > > NavList message boards:www.fer3.com/arc
    > > Or post by email to: NavList@fer3.com

    > > To , email NavList+@fer3.com<NavList%2B@fer3.com>

    >
    >

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    To , email NavList+@fer3.com

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    Or post by email to: NavList@fer3.com
    To , email NavList+@fer3.com

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