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Author Topic:   Replacing Loran on 21 W/A
critch22 posted 06-19-2003 04:12 PM ET (US)   Profile for critch22   Send Email to critch22  
Does anyone know if 93 Loran transducer is adaptable to a new Garman sounder/plotter unit (168) - and is installation easy or should it be left to the pros?
GeneNJ posted 06-19-2003 07:55 PM ET (US)     Profile for GeneNJ  Send Email to GeneNJ     
Why would you consider doing this?
jimh posted 06-20-2003 12:05 AM ET (US)     Profile for jimh  Send Email to jimh     
LORAN does not use transducers.

I guess you might be referring to the LORAN antenna. A LORAN antenna is designed to perform most effectively over a narrow band centered at 100 KHz or 0.1 MHz.

A GPS does not use a transducer.

I guess you might be referring to an external antenna for use with a GPS receiver. The GPS signals are transmitted on very high frequencies, on the order of thousands of Megahertz (MHz).

Because these is an difference in the design frequencies between a LORAN antenna and a GPS antenna (about four orders of magnitude or a ratio of 1:10,000) it is unlikely that one could make use of a LORAN antenna as a suitable external antenna for a GPS.

There are some GPS units that utilize a second channel of information, called Differential GPS, and this information is transmitted in the 310 KHz band. Again, it is doubtful that a LORAN antenna would work well for this application.

If I have misunderstood your question, it may be caused by your unusual reference to "transducers" in connection with LORAN receiver. That really makes no sense to me, but I have tried to read between the lines of your article and offer some advice that might apply.

critch22 posted 06-20-2003 10:52 AM ET (US)     Profile for critch22  Send Email to critch22     
I am the first to admit that I am clueless. Thank you for the info. What I have is a Loran (charts/depths/temp/etc.) unit that seems to me to be outdated. Because I have a laptop and because the Garmin 168 includes software I can upload maps into the unit to aid in navigation. So that should eliminate the need for Loran, Right? The depth finder within the unit does not work - and I believe it is connected to a transducer (isnt that the little black thing that has a paddle wheel and a cable) mounted on the transom at water level. My question is (nothing to do with antenas really) but will the transducer I have on the boat work with the new Garmin unit? Or will I have to buy a new transducer? And if I do - how difficult is all of this to instal?
tuna1 posted 06-20-2003 12:23 PM ET (US)     Profile for tuna1  Send Email to tuna1     
A little background info would be helpfull to answer your request.
1.What make model is the present loran set.
2.You say the depth sounder does not work.The cable for the depth sounder,should be a single screw in type connection-that contains atleast 6 pins to supply the required info to the display head. Most likely there is a broken wire at the connector.There should be a tag/label somewhere along that wire to the transducer that contains info about the attached depth tranducer.
3. In order to answer your question about the reuse of this present tranducer,that info tag/lable must be found.
4.If you can post the above info/answers, we should be able to help you out.
hauptjm posted 06-20-2003 12:26 PM ET (US)     Profile for hauptjm    
Ahh, Loran brand sounder, not a Loran navigational device! The short answer is it probably won't work. My very simple (less than neophyte) understanding is that the transducer manufactured to match the unit is just that, manufactured to match the unit. The installation is relatively easy, and you can use the existing wiring as a "sender" to run the new wiring.

Otherwise, I'm still confused. The "paddlewheel" device you describe sounds like nothing more than a sending unit for speed. Transducers are more typically flat, somewhat bulbous shaped plastic. You also state that the existing unit has "charts/depth/temp./etc." The "charts" part is confusing. The remaining description sounds like a traditional sounding device. The "charts" portion sounds like a GPS navigational device. Navigational devices don't capture their information via a transducer, but rather via an antenna. Hence, jimh's response.

Now, is that clear as mud.

Backlash posted 06-20-2003 12:27 PM ET (US)     Profile for Backlash  Send Email to Backlash     
First of all, you do not need the loran if you are going to use the Garmin.

If I understand correctly, you have a combimation loran/sounder and the depth sounder doesn't work. Correct? The "paddle wheel" you are referring to is probably NOT the transducer, but more likely the speed/temp sensor for the sounder. The actual transducer is normally mounted on the other side of the engine from the speed/temp unit. It would help if you identified the make and model of the loran/sounder.

Finally, if in fact you have a transducer for the loran/sounder, it will not work with your Garmin. You will have to buy a tranducer specifically for your Garmin 168.

Installation is not that difficult, it just requires running cables thru the transom and under the floor to the helm area. Since it appears cables are already run, they could be used to pull the new cables thru.

Steve

critch22 posted 06-20-2003 12:40 PM ET (US)     Profile for critch22  Send Email to critch22     
jimh: Please add an "Amature Forum."

I believe the little paddle wheel is for measuring speed. "Chart" is just what the guy said whe I asked said - "whats this do?" Isnt Loran a series of coordinates in the water that corresponds to special maps? Doesnt GPS replace that - essentially? The bottom line is, I live in south Florida and I don't have a depth finder. I thought - why not get a GPS/Depth-Sounder/Fishfinder combo? As long as I can use the same wire, I think I can manage the installation.

critch22 posted 06-20-2003 12:57 PM ET (US)     Profile for critch22  Send Email to critch22     
Steve, you have the same boat as me. What a boat! (5' chop two weeks ago off Palm Beach - no problem)
I never want to use the loran for anything, it will stay put (flush mounted)for looks only. The Garmin will be mounted on the flat surface above by the compass. So I'll buy it, the new transducer - and instal it. As long as I can use the same cable that runs from the helm to the transom I am okay... :) Thanks to all!
tuna1 posted 06-20-2003 02:46 PM ET (US)     Profile for tuna1  Send Email to tuna1     
CATCH 22

If i were you i would maintain the Loran to make it operational and use it as a backup unit for navigation.

Loran # do not convert to GPS corordinates in Lat/Lon and maintain their accuratecy very well.But if you have good loran #,or can obtain some from the locals for some fishing hot spots,you can return over the spot and drop baits down time after time with a working loran set.

Most likely you should run a new transducer with wire,along the old wire,mount it on the other side of the transum,and then to the new Garmin GPS unit.

I would like to see the older transducer wire/plug repaired so it can be used as a back up to the new electronics for depth,temperature and speed.

May i email you with more complete instructions as to what to do?

HAPPYJIM posted 06-20-2003 03:58 PM ET (US)     Profile for HAPPYJIM  Send Email to HAPPYJIM     
Stay as far away from your compass with any electronics.
It will make the compass not as accurate.
critch22 posted 06-20-2003 04:35 PM ET (US)     Profile for critch22  Send Email to critch22     
Tuna, very interesting. Email me whatever you want... Many thanks...

Thanks for the tip on the compass.

The current unit probably does work - though i have no idea how to work it. I assume its a 1993 unit - great for backup I guess. Theres a purple blob though in the lower right corner - and I think thats whats preventing me from seeing the depth...

hauptjm posted 06-23-2003 11:08 AM ET (US)     Profile for hauptjm    
Critch,

Back to your origianl question:
1. The existing transducer (if there is one) will not work.

2. The Garmin unit should have come with the appropriate transducer, you'll have to run that one and you can use the existing wire as a "sender".

3. Loran availability is destined to the dust-bin in the very near future. (I forget the year, but it's around the corner). Since, it is dependent on the radio signals that create it, when the transmission ends, so does Loran. Hence, pitch the unit: they were never as accurate as GPS is anyway.

p.s. GPS (just like Loran) will require an antenna, so the placement and wiring will have to be addressed. Again, if you have an antenna for the Loran unit, and like the placement, you can use that wiring as a sender as well.

jimh posted 06-24-2003 12:57 PM ET (US)     Profile for jimh  Send Email to jimh     
Given the pace of technology these days, marine electronics are like athletic shoes. You buy them, use them for two or three years, you get some new ones.

It may be that marine electronics are also less expensive than athletic shoes, too. :-)

I would not fiddle with ten year old electronics that don't work. Remove all the old stuff and get some new stuff.

The one drawback is the old stuff left holes. You'll have to deal with that.

Also--Is there really a brand name marine manufacturer that is called "Loran"?

Sixty year old LORAN-C has held up well, considering it has been around since the 1940's. If we jumped ahead to 2063 I bet that today's GPS won't be there to meet us.

hauptjm posted 06-24-2003 02:56 PM ET (US)     Profile for hauptjm    
jimh,

You know you got me thinking, and I do know of a Lowrance Brand, but not a Loran Brand. The old brain must be playing tricks! Regardless, I believe you to be correct that the rate of development in electronics will far outpace what we have seen in the last 30-40 years. But then that seems to be the case in technology as a whole. In the time I've been racing sail boats, we've gone from dead reckoning to lorans and radar to interphased DGPS/Radar/Charting. In fact, GPS has gotten more accurate with the expansion of the frequencies in a relatively quick time.

I have a client that is working on a device to aid navigation that utilizes something like 10,000 data points that he developed in the military that is now declassified, and uses this information to compute weather and location to determine the most effective route from waypoint to waypoint. In fact, the data is reconciled against GPS for instantaneous correction. Who knows what's on the horizon.

critch22 posted 06-25-2003 07:43 AM ET (US)     Profile for critch22  Send Email to critch22     
Thanks to you all! I feel I am a wealth of knowledge because of all the great info I got of this post...

My problem is - i have bought the South Florida Boat Trader every week for ten years, I read it where most of us read it, and all the words just blurred together.

It is a Loran Unit, made by Raytheon. To view its screen would be like walking into an out-of-commission Pizza Hut that thrived in the eighties, sitting down with a pitcher of utlra-strong Pepsi, and playing PacMan on one of those tables that had the video game right below the surface.

I did buy the Garmin GPSmap 168 on Friday - built-in antenna, new transducer, etc. I shied away from an installation attempt when I looked behind the instrument panel of the 21 and realized I was out of my league... The only place I even saw a red & black was the 12V adapter.

Not to mention running the transducer, drilling into the hull, etc...

Thanks again Guys...

triblet posted 06-25-2003 11:53 AM ET (US)     Profile for triblet  Send Email to triblet     
jimh, a LORAN antenna will work just fine for differential
GPS. The frequencies are close enough. But a coat hanger
would work pretty well down there too.

However, in the US, WAAS has pretty much made DGPS obsolete.


Chuck

jimh posted 06-25-2003 01:10 PM ET (US)     Profile for jimh  Send Email to jimh     
Chuck, As you point out, and as a million cars on the road with coat hangers in use as car radio antennas also demonstrate, you can use almost any piece of conductive rod as an antenna. I just said that an antenna tuned to 0.100 MHz will not work well at 0.300 to 0.350 MHz, the approximate range of the DGPS transmissions.

LORAN signals at 0.100 MHz are transmitted at very high power, typically about 100 KW or more.

The DGPS transmitters are much lower power, maybe a KW might be typical. Of course, you are not as far from the DGPS station as from the LORAN; their range is only a 150-200 miles. Having a proper DGPS antenna might significantly affect how well you can receive them.

Many years ago I was experimenting with my car radio antenna. You will note that most car radio antennas are equipped with an odd style of coaxial cable, usually one with 93 ohm characteristic impedance or higher. I though I'd make a new cable for the antenna and use 52-ohm coax. That way I might be able to trim the antenna and use it as a quarter wave on 145 MHz.

I wired this all up and tried it out. It worked fine on 145 MHz, however the car radio ceased to be able recieve anything but the loudest stations. In most low frequency systems (LF) a short antenna is very highly reactive, and changing anything in the system causes a major change in the tuning. I think the reason they use 93-ohm coax is to keep the shunt capacitance as low as possible. When I changed to 52-ohm the performance was severly degraded. Receiver sensitivity went down about 30 dB. I also suspect that the feedline length change was significant and the RF amplifier in the AM receiver was carefully tuned to compensate for the original coax and length of feedline.

So that is my first hand experience with how well a small LF antenna works if anything is changed, i.e., not very well. From this I make the leap that one tuned for 0.100 will probably not work optimally at 0.350 Mhz. Of course, if the LORAN antenna is a broadly tuned e-probe type of antenna, it may be possible that it has enough bandwidth to work over the 3:1 jump in frequency. I've seen some little probe antennas that give a good account of themselves over very broad freequency ranges. But in that case the receiver must supply an operating voltage to the antenna and there might be problems with the connector and pin-out, the voltage supplied, if any, and other problems of using an older LORAN antenna for DGPS applications.

The Army Corps of Engineers has a DGPS transmitter site just a few blocks from where I work, and I tried to visit it. This was even before 9/11. I think it might be easier to get a tour of Fort Knox than to arrange to see the DGPS transmitter site.

By the way, LORAN is not dead. According to this website it is planned to be maintained as a back up for GPS until at least 2008. It is not dead, but just approaching retirement age.

http://webhome.idirect.com/~jproc/hyperbolic/loran_c_future.html

BillD posted 06-25-2003 02:18 PM ET (US)     Profile for BillD  Send Email to BillD     
critch 22 :

To me it sounds like the original unit had Loran (maybe charting) Depth, speed, water temp, and maybe also a fishfinder. The Garmin 162 is just the GPS. I would consider talking to a marine electronics dealer to find a unit that will fit the hole that the Loran is in and provides as much functionality as possible. I find my depth finder invaluable for navigation and fishing. Yes this will cost more money, but the instalation will not be too bad since there is already something there. You will also be very happy with the results. Raytheon has kept many of their flush mount cases in simmilar sizes for years so they may have something that drops in.

On the otherhand if you really just want a GPS / Chartplotter that you can download stuff from your computer from and is easy to install I would return the Garmin 162 and get the Garmin 176. The big difference is that the 176 can also run on batteries as well as being wired. This makes it easy to program because you can take it off the boat easily. It also can be used in your car or anywhere else.

critch22 posted 06-25-2003 05:04 PM ET (US)     Profile for critch22  Send Email to critch22     
Bill, the Garmin I bought is a 168, not a 162. The 168 actually has GPS, Depth and Fishfinding capability. The Raytheon will stay put for a while - I think it does have a fish finder in it - until I sell the boat and get that 27 Full Cabin. And when I do sell it, The Smithsonian will get dibs on the vintage Raytheon...

Jim: Call down to Edgewater - get them to sign a book-deal with you. You must put Dick Fisher's dream/saga on every coffee table on the coast...

JohnJ80 posted 06-25-2003 11:42 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
Having used Loran to navigate for many years, and having had more than my fair share of frights due to inaccuracy in proximity to land on Lake Superior during bad weather yacht racing, I wouldn't use a Loran to back up anything except the bottom of the trash can. There is a special fright when you are naviating in fog and plotting the location that the Loran give you and finding out that it shows you to be a mile inland. I never want to see another TD delineated chart as long as I live.

Besides that, I am not sure that I would trust an old Loran receiver. The electronics will have aged and the technology is essentially analog. Drift in the receiver could influence accuracy. I would not rely on it unless I had carefully checked it to make sure I believed it. I mean, Loran is basically a fancy version of radio direction finding. The lay of the intervening land can effect it especially with a weak signal.

If you need backup, buy a handheld GPS and a pocket full of AA batteries. Learn how to plot and Dead Reckon on an official chart and you will have three systems and two backups - a chart plotter, your handheld GPS on and your paper chart, and your DR plot. There is no excuse for serious navigating to not be periodically (like every 15 minutes or so) recording your position on a DR plot. That is, unless, you aspire to be one of the subjects of the chapters in the next revision of the book 'Total Loss'.

just my $0.02.

Good choice with the Garmin unit.

j

BillD posted 06-26-2003 10:55 AM ET (US)     Profile for BillD  Send Email to BillD     
Sorry Critch22 - my reading skills are a bit rusty - Then ignore everything I said.

Bill

jimh posted 06-26-2003 11:15 AM ET (US)     Profile for jimh  Send Email to jimh     
When I mention LORAN being used as a backup, I don't mean as a backup for your individual GPS receiver aboard your boat, I mean as a backup system of navigation and position finding in the event of a widespread outage of the GPS System.

Also, there is nothing in common between Radio Direction Finding and LORAN in terms of their underlying techniques.

The underlying method of LORAN and GPS is very similar, they just use different frequency signals and have their reference stations located in different places (earth versus in orbit).

There is nothing really "digital" about GPS. It sends radio signals out and your receiver receives them, just like LORAN. Your receiver deduces your position based on the time intervals between the arrival of the signals, just like LORAN. Your GPS receiver has much more computational power than an old LORAN receiver, but that does not make the underlying principals of the system "digital".

GPS suffers from several problems:

--operated by the Department of Defense and subject to intentional interruption of service and accuracy; LORAN is operated by the Coast Guard.

--extremely low power transmission and subject to interference by simple jamming techniques; LORAN uses extremely high power and is difficult to jam.

--poor coverage in urban areas, although this is not a problem usually when at sea.

There is no doubt that the current GPS receivers have progressed far beyond the typical 1980 LORAN receiver in their capabilities.

jimh posted 06-26-2003 11:17 AM ET (US)     Profile for jimh  Send Email to jimh     
When I mention LORAN being used as a backup, I don't mean as a backup for your individual GPS receiver aboard your boat, I mean as a backup system of navigation and position finding in the event of a widespread outage of the GPS System.

Also, there is nothing in common between Radio Direction Finding and LORAN in terms of their underlying techniques.

The underlying method of LORAN and GPS is very similar, they just use different frequency signals and have their reference stations located in different places (earth versus in orbit).

There is nothing really "digital" about GPS. It sends radio signals out and your receiver receives them, just like LORAN. Your receiver deduces your position based on the time intervals between the arrival of the signals, just like LORAN. Your GPS receiver has much more computational power than an old LORAN receiver, but that does not make the underlying principals of the system "digital".

GPS suffers from several problems:

--operated by the Department of Defense and subject to intentional interruption of service and accuracy; LORAN is operated by the Coast Guard.

--extremely low power transmission and subject to interference by simple jamming techniques; LORAN uses extremely high power and is difficult to jam.

--poor coverage in urban areas, although this is not a problem usually when at sea.

There is no doubt that the current GPS receivers have progressed far beyond the typical 1980 LORAN receiver in their capabilities.

jimh posted 06-26-2003 11:17 AM ET (US)     Profile for jimh  Send Email to jimh     
When I mention LORAN being used as a backup, I don't mean as a backup for your individual GPS receiver aboard your boat, I mean as a backup system of navigation and position finding in the event of a widespread outage of the GPS System.

Also, there is nothing in common between Radio Direction Finding and LORAN in terms of their underlying techniques.

The underlying method of LORAN and GPS is very similar, they just use different frequency signals and have their reference stations located in different places (earth versus in orbit).

There is nothing really "digital" about GPS. It sends radio signals out and your receiver receives them, just like LORAN. Your receiver deduces your position based on the time intervals between the arrival of the signals, just like LORAN. Your GPS receiver has much more computational power than an old LORAN receiver, but that does not make the underlying principals of the system "digital".

GPS suffers from several problems:

--operated by the Department of Defense and subject to intentional interruption of service and accuracy; LORAN is operated by the Coast Guard.

--extremely low power transmission and subject to interference by simple jamming techniques; LORAN uses extremely high power and is difficult to jam.

--poor coverage in urban areas, although this is not a problem usually when at sea.

There is no doubt that the current GPS receivers have progressed far beyond the typical 1980 LORAN receiver in their capabilities.

JohnJ80 posted 06-26-2003 05:47 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
jimh,

I think we are saying the same thing but I need to clarify.

Sure - neither gps or loran are 'digitial' signals in the sense that they are rf transmitted. Both have time delay information decoded in them.

Having worked with an electronics tech in tweaking and tuning a late '80s early '90s Loran unit (actually a couple of them) and being an EE myself, i can assure you that the signal processing of a Loran unit is far more analog than digital.

However that is more a function of technology of the times each was designed. If new Loran units were being designed today for a growing market segment, then they would have the same level of digital processing that today's GPS does. Today's GPS systems are pretty much SOC (System on a Chip) technology and can be very complex huge integrated circuits. The DSP (Digital Signal Processing) that gets done in GPS was just not available. So instead of it being a compute problem alot of it was done with analog oscillators and filter circuitry. Our current digital technology is orders of magnitude above the stuff available in the heyday of Loran.

Its not that you can't make a digital loran at the same level of technology as GPS today, but why would you? It just isn't worth the expensive R&D to support a technology that will go a way shortly when a better one (GPS is so available).

So, inside a Loran receiver you have lots of analog components that can drift with time and temp and where the compensation is not monitored unless you take your unit in and have someone look it over periodically.

If you take a unit of that vintage, it is almost gospel that the thing will have drifted in one direction or another. Given that Loran has nowhere near the accuracy of GPS, you can be talking about pretty large error radius' on your plot.

The other thing that you didn't mention is that the signals from GPS satelites are much higher integrity since they are not subject (as much) to the bending effects far afield as are Loran signals. Variance in the shape of the earth and other factors I don't really understand can cause the Loran radials to bend with the earth from the tower leading to inaccuracy. Boy, do I have first hand experience with that one when the USCG took down a transmitter that covered Lake Superiour in the early 90s. Got a little interesting at times.

by comparing Loran to RDF, I meant it has alot of the same inaccuracy problems as does RDF in that it is an earth bound transmiter close to the earth's surface with the bending, the reliability of transmitters due to weather and natural disaster etc.. Actually, to put a point on it, RDF Loran and GPS are all RDF techniques with the last two having encoded timing data embedded. And yes, I have used all of them to do some serious navigation in fog and bad weather.

Make more sense?

I still never want to see another Loran reciever on any boat I'm on. It may be quaint to navigate that way, but I'll bring my garmin GPS12Map instead.

j


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