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'[EE]: loran C'
2006\01\20@080922 by Wouter van Ooijen

face picon face
Are there any do-it-yourself Loran C receiver designs available? Yes, I
did google, but found one.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\01\20@100001 by Neil Baylis

picon face
I was loking recently, to find one I could use as a timing reference.
I found nothing useful. Although I do seem to remember seeing at least
one schematic with some discussions. However, there are plenty of used
LORANs available on eBay.

If you just want to extract timing info from the LORAN signal, it's
not too complicated. Using it for navigation requires a whole bunch of
precise math as well as the ability to time the arrival of the LORAN
pulses. You have to pick out a particular point on a particular cycle
of the 100 kHz signal as your timing reference.

In the end, I gave up and bought a GPS timing module instead, and
that's working fine for me. I don't need it for navigation, just for a
very stable 1 Hz reference signal.

Neil

On 1/20/06, Wouter van Ooijen <spam_OUTwouterTakeThisOuTspamvoti.nl> wrote:
{Quote hidden}

> -

2006\01\20@102309 by Wouter van Ooijen

face picon face
> If you just want to extract timing info from the LORAN signal, it's
> not too complicated. Using it for navigation requires a whole bunch of
> precise math as well as the ability to time the arrival of the LORAN
> pulses. You have to pick out a particular point on a particular cycle
> of the 100 kHz signal as your timing reference.

I fellow teacher was interested in the possibility of using it for
mobile robot position information. We do electronics and embedded, some
work was expected, both analog and digital.

Did you find usefull reference information?

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\01\20@131100 by Neil Baylis

picon face
--> Did you find usefull reference information? <--

Yes, there are a few places on the net where you can find the signal
specification, and how the system works. It's a lot simpler than GPS. Just
google for LORAN C Signal specification, and you should find it. That will
give you pretty much all the info you need for decoding the signal.

You'll need to build a tuned RF 100 kHz receiver. If you google for info
about VLF radio, you'll find amateurs who construct receivers that will pick
up the signal. In fact, many of the discussions relate to how to get rid of
that damned LORAN signal because it is transmitted with such high power.
Search also for WWVB receivers, as many of those are suitable. (Note, its
WWVB, which transmits at 60 kHz, not WWV which transmits at much higher
frequencies).

They usually use some kind of B field antenna, shielded from the E field.
I've seen plans for one that was made from the rim of a bicycle wheel. It's
all very doable, especially if you have a scope. Google for "loop antenna"
or "VLF antenna".

You can also buy LORAN antennas that are already tuned for the right
frequency. They use them for small aircraft and boats. There are usually a
few on eBay.

I suspect the RF part will be relatively simple, but then you'll have the
job of decoding the pulses and measuring their arrival time. Depending on
where you are in the world, the signal has different timing characteristics.
You have to recognise these patterns to know which LORAN chain you are
listening to. Then you have to identify the master transmitter in the chain,
and 2 or 3 slaves. You'll need a very precise, stable crystal oscillator. I
would suggest oven stabilized, or at least temperature compensated. Some
receivers generate their timing from the 100 kHz carrier, which is locked to
a caesium clock. WHatever method you use, you'll need to timestamp as
precisely as possible the time of arrival of each pulse in the chain. Each
pulse is a burst of carrier of an exactly defined shape. You have to
identify a particular point within the burst as the time reference for that
burst. The reference point is something like the third zero crossing of the
carrier. When you have the timestamps for all the pulses, you then apply the
math and solve for your position.

I still like the idea of building one of these, even though I have no use
for it now.

Neil


On 1/20/06, Wouter van Ooijen <.....wouterKILLspamspam@spam@voti.nl> wrote:
{Quote hidden}

> -

2006\01\20@211723 by Vic Fraenckel

flavicon
face
>I fellow teacher was interested in the possibility of using it for
>mobile robot position information.

Wouter,

Loran might get you a position to 50-60 meters after much development work on your part, but for one hell of a lot less work and money you can get down to a couple of meters of position with a cheap GPS module. I can understand an intellectual pursuit but what will you have in the end?

Just my 2 cents!

Vic
________________________________________________________

Victor Fraenckel - The Windman        
victorf ATSIGN windreader DOT com
KC2GUI                                                  

2006\01\20@232820 by VULCAN20

picon face
Vic Fraenckel wrote:

>>I fellow teacher was interested in the possibility of using it for
>>mobile robot position information.
>>    
>>
>
>Wouter,
>
>Loran might get you a position to 50-60 meters after much development work on your part, but for one hell of a lot less work and money you can get down to a couple of meters of position with a cheap GPS module. I can understand an intellectual pursuit but what will you have in the end?
>
>Just my 2 cents!
>
>Vic
>
Isn't the government or who ever takes care of the loran stations
supposed to stop upkeep on the some time soon  also?

>                      
>  
>

2006\01\21@041520 by Wouter van Ooijen

face picon face
> Loran might get you a position to 50-60 meters after much
> development work on your part, but for one hell of a lot less
> work and money you can get down to a couple of meters of
> position with a cheap GPS module. I can understand an
> intellectual pursuit but what will you have in the end?

Actually it was the idea of another teacher, but the answer is of
course: something interesting for our students to do! And from what I
read Loran C can be better than 50-60 meters in repeatability (!=
accuracy), which is what matters for a roaming robot.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\01\21@083622 by Brady

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face
I agree,

Especially when the GPS modules are only 50 bucks.

Brady


-----Original Message-----
From: piclist-bouncesspamKILLspammit.edu [.....piclist-bouncesKILLspamspam.....mit.edu] On Behalf Of
Vic Fraenckel
Sent: Friday, January 20, 2006 9:17 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE]: loran C

>I fellow teacher was interested in the possibility of using it for
>mobile robot position information.

Wouter,

Loran might get you a position to 50-60 meters after much development work
on your part, but for one hell of a lot less work and money you can get down
to a couple of meters of position with a cheap GPS module. I can understand
an intellectual pursuit but what will you have in the end?

Just my 2 cents!

Vic
________________________________________________________

Victor Fraenckel - The Windman        
victorf ATSIGN windreader DOT com
KC2GUI                                                  

2006\01\21@083913 by John Nall

picon face
Wouter van Ooijen wrote:
> > And from what I
> read Loran C can be better than 50-60 meters in repeatability (!=
> accuracy), which is what matters for a roaming robot.
>
>  
Well, I can confirm it from experience for you.  I use Loran C all the
time, in fishing, and once you find a spot and have the Loran C
coordinates for  that spot, you can go back to it with great accuracy.  
What you cannot do is go to a spot for the very first time (using just a
chart with Loran C coordinates superimposed upon it) with accuracy.

So far as the government stopping support, they have been threatening to
do that for a long time now here in the U.S. but have not yet done so.  
There is a fairly well-organized coalition of fishermen (both commercial
and recreational) who lobby for continuation of the service.  And it
doesn't cost that much to maintain the stations.  The real problem is
that it is almost impossible to buy new Loran C receivers any more, so
people are trying their best to get all those Loran C fishing spots
converted to GPS fishing spots.  Once that is far enough along, then I
would guess that it will gradually be phased out.

2006\01\21@110526 by Neil Baylis

picon face
>From my understanding, it was originally thought that GPS superseded
LORAN C, and the LORAN was slated for termination. However later many
folks protested, and in addition it was realized that there were
scenarios that would result in total GPS failure (Due to hostile
attacks) but that LORAN was more viable due to its distributed nature.
I.e., if you attack a single LORAN station, all the others keep
operating. To take out the whole thing, you would have to destroy many
stations, all over the world. So they decided to keep it going, and
have recently finished upgrading all the US LORAN stations.

Apparently, due to the low power of the GPS signal, it would be
relatively easy to jam. Whereas the LORAN signal has very high power,
and would therefore be more difficult to jam.

I think you can buy new receiverfs that incorporate both LORAN and
GPS, so you can get a fix in situations where no satellites are
visible.

If this is a student exercise, I think doing it with LORAN is far more
feasible than with GPS, even though the resulting accuracy may be
different. I personally would never attempt to design a GPS receiver,
but I think I could easily succeed at designing a LORAN C receiver.

Neil

On 1/21/06, John Nall <EraseMEjwnallspam_OUTspamTakeThisOuTgmail.com> wrote:
{Quote hidden}

> -

2006\01\21@114947 by John Ferrell

face picon face
I have a Palomar VLF converter that up converts to my Ham Transciever.
Putting Loran signals on a scope is not difficult. It sounds like a do able
project to me. If commercial equipment sources are drying up, it could a
popular kit.
John Ferrell
http://DixieNC.US

{Original Message removed}

2006\01\21@124024 by Brooke Clarke

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face
Hi Wouter:

I'd be interested in learning what you find in the way of LORAN-C kits.  
Note that the LORAN-C signal is made up of pulses so a receiver needs to
have the bandwidth to pass them.
I built a Group Repetition Interval (GRI) generator some decades ago.  
It was a divider programmable using 3 thumb wheel switches.
When the GRI pulse is used to trigger a scope all the pulses in that
chain stay still and all the other GRI pulses appear at random places.
The master station has more pulses in it'sgroup than the slaves so it's
easy to find the master.  Then by measuring the time delay between the
various pulses you can find you position.  With my crude setup the
location was within maybe a mile.

For circuit diagrams using mostly discrete parts I have a CD-ROM with
many Austron manuals for sale at:
http://www.pacificsites.com/~brooke/A2100F.shtml#Man

Note that although the LORAN-C system was designed for coastal
navigation it can also be used for precision timing.  The AUstron 2100T
receiver is designed to do this and when receiving a nearby station
works about as good as GPS.

Have Fun,

Brooke Clarke, N6GCE

--
w/Java http://www.PRC68.com
w/o Java www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

Message: 56
Date: Fri, 20 Jan 2006 14:09:20 +0100
From: "Wouter van Ooijen" <wouterspamspam_OUTvoti.nl>
Subject: [EE]: loran C
To: "'Microcontroller discussion list - Public.'" <@spam@piclistKILLspamspammit.edu>
Message-ID: <000501c61dc2$ba56cef0$0b00a8c0@PAARD>
Content-Type: text/plain;        charset="us-ascii"

Are there any do-it-yourself Loran C receiver designs available? Yes, I
did google, but found one.

Wouter van Ooijen

2006\01\21@135546 by Peter

picon face

> Apparently, due to the low power of the GPS signal, it would be
> relatively easy to jam. Whereas the LORAN signal has very high power,
> and would therefore be more difficult to jam.

Nothing is 'very difficult to jam' when the jammer is near the jamee,
because of the inverse square law.

Peter

2006\01\21@153656 by Denny Esterline

picon face
> >From my understanding, it was originally thought that GPS superseded
> LORAN C, and the LORAN was slated for termination.

<snip>

I don't claim to be an expert, but when GPS made way for Differential GPS
wasn't it the LORAN system they used to add that capability?

It's been a long time since I was concerned about such things so my memory
is a little fuzzy, but I thought they placed high end GPS receivers at the
LORAN stations. Since the receivers are fixed and at precisely known
locations the difference between GPS located and actual location can be
calculated and used as a local correction value. I _thought_ this signal was
added to the LORAN broadcast signal. If all this is as I remember it,
wouldn't that suggest the LORAN system will be with us for many years to
come?

Wouldn't be the first time I was wrong though, heck, not even the first time
today. :-)

-Denny


2006\01\21@160558 by Stef Mientki

flavicon
face


Wouter van Ooijen wrote:

>Are there any do-it-yourself Loran C receiver designs available? Yes, I
>did google, but found one.
>
>  
>
hi Wouter,
with ixquick (better for these kind of things) you would have found this one
http://phk.freebsd.dk/loran-c/
Stef

>Wouter van Ooijen
>
>-- -------------------------------------------
>Van Ooijen Technische Informatica: http://www.voti.nl
>consultancy, development, PICmicro products
>docent Hogeschool van Utrecht: http://www.voti.nl/hvu
>
>
>  
>

2006\01\21@162456 by Wouter van Ooijen

face picon face
> > Apparently, due to the low power of the GPS signal, it would be
> > relatively easy to jam. Whereas the LORAN signal has very
> high power,
> > and would therefore be more difficult to jam.
>
> Nothing is 'very difficult to jam' when the jammer is near the jamee,
> because of the inverse square law.

When compared to GPS it is certainly true that loran C will be
relatively difficult to jam. Whether you would call that difficult in
some absolute sense is up to you.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\01\21@162649 by Wouter van Ooijen

face picon face
> with ixquick (better for these kind of things) you would have
> found this one
> http://phk.freebsd.dk/loran-c/

Hi Stef! Yes, I found that one, but I am not sure it is realy helpful.
But interesting reading.

Now what I would like to find is an analog front end, up to where I can
add a fast A/D and a fast uC.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\01\21@180002 by w d myrick

picon face

----- Original Message -----
From: "Wouter van Ooijen" <KILLspamwouterKILLspamspamvoti.nl>
To: "'Microcontroller discussion list - Public.'" <RemoveMEpiclistTakeThisOuTspammit.edu>
Sent: Saturday, January 21, 2006 3:27 PM
Subject: RE: [EE]: loran C


> > with ixquick (better for these kind of things) you would have
> > found this one
> > http://phk.freebsd.dk/loran-c/

There is a transistor receiver construction project for wwvb (60 Khz) in ham
radio back in the 80s. If you are interested I will look it up and email you
a copy.
you can reply to me off list.

Derward  KD5WWI

2006\01\22@155006 by Peter

picon face


On Sat, 21 Jan 2006, Wouter van Ooijen wrote:

{Quote hidden}

Knowing how hard it is to receive on LW around most large cities I will
make no assumptions, excepting that the S/N ratio for GPS may be much
better.

Peter

2006\01\23@095954 by arrows

flavicon
face
w d myrick wrote:
> ----- Original Message -----
> From: "Wouter van Ooijen" <spamBeGonewouterspamBeGonespamvoti.nl>
> To: "'Microcontroller discussion list - Public.'" <TakeThisOuTpiclistEraseMEspamspam_OUTmit.edu>
> Sent: Saturday, January 21, 2006 3:27 PM
> Subject: RE: [EE]: loran C
>
>
>
>>>with ixquick (better for these kind of things) you would have
>>>found this one
>>>http://phk.freebsd.dk/loran-c/
>
>
> There is a transistor receiver construction project for wwvb (60 Khz) in ham
> radio back in the 80s. If you are interested I will look it up and email you
> a copy.
> you can reply to me off list.
>
> Derward  KD5WWI
>
There is another article in Communications Quarterly in the Fall 1991
issue Pages 20-32. This is authored by Randy Evans, KJ6PO and David
Evans, N6UEZ.
Hope this helps.
arrows

2006\01\23@204315 by Russell McMahon

face
flavicon
face
>>>>with ixquick (better for these kind of things) you would have
>>>>found this one
>>>> http://phk.freebsd.dk/loran-c/

FWIW, IXQUICK and GOOGLE both had that as their first choice (if you
ignore the unrelated paid ads above it) when fed with

       loran c receiver

which I though was pretty good on both their parts.


       RM


'[EE]: loran C'
2006\02\07@181053 by w d myrick
picon face
Wouter,  Did you get the article I sent you about the 60 Khz receiver?

Derward  


----- Original Message -----
From: "Wouter van Ooijen" <RemoveMEwouterspamTakeThisOuTvoti.nl>
To: "'Microcontroller discussion list - Public.'" <piclistEraseMEspam.....mit.edu>
Sent: Saturday, January 21, 2006 3:27 PM
Subject: RE: [EE]: loran C



> But interesting reading.
>
> Now what I would like to find is an analog front end, up to where I can
> add a fast A/D and a fast uC.
>
> Wouter van Ooijen

2006\02\08@034428 by Wouter van Ooijen

face picon face
> Wouter,  Did you get the article I sent you about the 60 Khz receiver?

Yes I did, many thanks. Yesterday I took it to the school to print it
out (no laser at home) and handed it to the teacher who came up with the
Loran C idea, he is more into analog stuff than I am. We will net you (=
the list) know when we have any results, but that can take a long long
time.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


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