NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: LORAN-C to be shut down.
From: John Huth
Date: 2009 Dec 9, 08:08 -0500
From: John Huth
Date: 2009 Dec 9, 08:08 -0500
Thanks, Gary. I was just using the normal formulas for inductance, etc. The most difficult part was for the ferrite stick - there's a huge range of magnetic permeabilities for ferrite, so I had to take a guess. These things should really come with a certification of the permeability. That's what I get for buying from a fly-by-night ferrite stick retailer.
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On Wed, Dec 9, 2009 at 5:23 AM, glapook@pacbell.net <glapook@pacbell.net> wrote:
You might like this site which calculates loop antenna data.
http://www.mindspring.com/~loop_antenna/amloop_calc4.htm
gl
On Dec 6, 8:01 am, Apache Runner <apacherun...@gmail.com> wrote:
> Another enhancement, which is perhaps cheaper is the so-called sportsman's
> antenna. It consists of a large wire loop and tunable capacitor. You put
> the loopstick radio inside this - properly oriented. The idea of the
> sportsman's antenna came from the days when radio and TV stations close to
> pro-sports games were blacked out, and people would build these antennas to
> enhance the signal, so they could listen in on distant stations.
>
> It turns out that these are highly directional with very deep and well
> defined nulls. There's an article about this at the following PDF
>
> http://www.dxing.com/tnotes/tnote09.pdf
>
> Here you could take a radio like Gary's Grundig and place it inside the loop
> antenna and use it as an RDF. I'm curious about the precision one can reach
> with a device like this.
>
> On Sat, Dec 5, 2009 at 8:58 PM, Lu Abel <lu...@abelhome.net> wrote:> > On Sat, Dec 5, 2009 at 3:03 AM, glap...@pacbell.net <glap...@pacbell.net>wrote:
> > 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.
>
> >> <NavList%2B@fer3.com<NavList%252B@fer3.com>>
> >> 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: Bryant’s 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
>
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>
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