LORAN C

Yep. The US pulled the plug earlier this year:

Also Canada, Africa, and Russia.

Some European countries still have their systems running:

but my guess is when Galileo is fully operational, Europe will also pull the plug. That may be many years with the current rate of funding and progress:

Meanwhile their Loran-C system is still up mostly because they want to rely on a US controlled GPS system.

It depends on what you're trying to accomplish. Seen any cell phones with Loran-C for E911 location? Vehicle navigation systems with Loran-C? For many things, GPS is the only way it can be done (or done economically). Nobody wants a 10ft long amplified Loran antenna hanging off their cell phone.

I don't think you'll see the Loran zombie rise from the dead.

GPS has its problems, but the latest units are sufficiently sensitive to work even in a storm. Location is important and having your receiver antenna below deck may cause reception problems. Try some of the newer "high sensitivity" GPS receivers and see if it works any better. If below deck on a handheld, thing about a docking station and external mast mounted antenna:

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I hope LW RDF is still going , I liked the morse ident feature and its simplicity. I doubt , over some distance , it is any less accurate than Loran and no hyperbolic plots to deal with

Even if it is still transmitting, the likelyhood of you being able to receive it is dropping every day. Out in the ocean, on a sailboat, you can turn off all of the devices that radiate noise on those frequencies, but on land you can't.

In many large urban areas, it's just a large "cloud" of noise up to 15 mHz or so, with most of it below 4mHz.

So you will be able to clearly receive the noise but not find a signal.

On the other hand if you are out in the ocean with an RDF, you can just point it to the noise and find land. It may not be the land you want, but it will be land.

Geoff.

I'm sure aviation and military GPS units are as robust as loran. Consumer units might be helped by a better antenna.

Yep. They're still alive and well. I still have a Taiho automagic mechanically rotating LW RDF that I use for demonstrations. It's fun to watch the loop seek and maybe point. Some of the LW beacon stations are sending DGPS which have largely been replaced by WAAS technology. Hearing LW beacons more than a few miles from shore is tricky without a big antenna. You would probably be more successful using AM, FM, and TV stations for coastline navigation, than using the few LW stations.

Incidentally, the big problem with Loran-C was that it really didn't work more than about 100 miles offshore. That limitation sold considerable number of (pre-GPS) Transit and Omega systems as "backup" for Loran-C. At least they worked in mid ocean. Incidentally, I still have my Tamaya sextant and a Magnavox TRANSIT receiver in storage.

If you want to do it thyself, it's possible to do 2D TRANSIT(NAVSAT) doppler navigation if you can hear some LEO satellites, know the Keplarian elements, and can accurately measure and record the doppler shift as it passes overhead, using triangulation and trilateration. The NIMS system may still be alive on 149.985 and 399.970 with telemetry on 136.650 MHz although Keps appear to be lacking:

Have your spherical geometry reference book handy. I've never actually tried it, but it should be possible:

The Origins of GPS:

If we got a big solar storm, and most or all satellites got knocked out, along with ground power, the beacons may be the only route home.

I remember having to record Loran D, just another experimental site.

My thoughs exactly.. Unfortuantely loran could have been a backup useful for boats and airplanes within the range of the system.

Andy comments:

I designed the TI Loran C for aircraft 30 yrs ago and found that a 22 inch antenna would deliver the same S/N ratio as a longer antenna, since the antenna would pick up atm. noise and signal in the same ratio, and 22 inches was about where the noise figure of the electronics would exceed the atmospheric noise........ Still, a 22 inch antenna on a cell phone would make it hard to carry in your pocket. .... so your point is well taken.

:>))) Andy in Eureka, Texas

Andy comments:

The only way the antenna can be "better" is to have more gain. That requires the antenna to be more directional. Such is not a good idea 'in GPS since one needs a hemispherical pattern, to account for where all the satellites are.

It's true that some GPS units have a poor antenna, but that's a matter of cosmetics more than anything else. Many military units are handheld and therefore have the same problem. Any unit with a remotely mounted antenna will perform about the same as any other unit, whether military or commercial, since they are all designed to have a hemispherical pattern.

Just feel like talking....

Andy in Eureka, Texas

If so, nicely done. The commercial marine version was not so nice:

At $2100 in 1978, that's about $6200 in todays dollars. Ouch.

You're right about atmospheric noise being greater than what the what would justify a low noise front end. This limits the maximum sensitivity of all HF receivers. My problem was overload. There was so much noise (and signal) that I had to use a front end RF amp that dissipated about 1/2 watt just to remain linear. The amp had to be near the antenna to prevent picking up electronics crud via the antenna line and so we could use cheap coax.

The 8 or 10ft fiberglass whip antenna was a no brainer for marine use. The typical HF antenna 10ft and a matching antenna looked nice on the other side of the vessel. It it were done on an airplane, I'm sure the size would have been more of an issue. Shakespeare does make a

Ummm.... 1. Better match (VSWR) 2. Better front to back ratio 3. Fewer side lobes 4. Better looking pattern. 5. Smaller, cheaper, lighter, easier to build, etc. 6. Grounded design to avoid static electricity buildup. Gain is not the only thing that's important in antennas.

True. Antennas only redirect RF. The don't create any. If you need more signal in one direction, you have to steal it from another direction.

Not really. I've built a perfectly functional GPS antenna that has a pattern similar to a donut (torus) elevated off the ground with no gain directly overhead. For location purposes, overhead satellites are nearly useless because there's no doppler shift.

Ahem... There are two basic types of GPS antennas. Patch antennas and quadrifilar (QFA) antennas. Both have roughly a hemispherical pattern. The QFA antenna is "better" for some applications because the radiation angle extends closer to the horizon and below than does the patch antenna. There's no benefit for 2D positioning, but the lower radiation angle offers better altitude information. A patch antenna becomes less circular polarized and more towards elliptical polarization hear the horizon. Well, at the horizon, it's horizontally polarized which is good for a -3dB gain loss. QFA antenna remains fairly RHCP at the horizon.

If you look inside some of the higher end handheld and vehicle mounted GPS antennas, you'll find a QFA antenna. Garmin GPS 76

Kinda looks like it was designed to fit either a patch and QFA.

Agreed. The differences are small but if you're trying to squeeze the last bit of performance out of a handheld, it can be important.

A bit more detail on GPS antenna gain that might be of interest. The usual assumption is that all GPS patch antennas have the same gain. Nope. From one of my previous rants on iPhone GPS performance:

Sarantel makes ceramic QFA antennas with -2db to -3dBic gain:

For ceramic substrate backed antennas, size is everything. This has nothing to do with the iPhone 3G antenna, but does explain why a ceramic substrate quadrifilar antenna has -2dBic gain, while the much larger air dielectric version has +5dBic gain. I couldn't find comparative data for various size quadrifilar antenna, but the following on patch antennas shows the problem:

Typical peak gain for GPS patch antennas on standardized ground planes are following. 25mm Patch 5 dBi 18mm Patch 2 dBi 15mm Patch 1 dBi 12mm Patch 0.5 dBi 10mm Patch -2 dBi

The effective bandwidth of a GPS antenna is usually measured by the frequency band below -10dB return loss. A GPS ceramic patch bandwith narrows with size. Typical bandwidths for GPS patches are as follows 25*25*4 mm 20 MHz 18*18*4 mm 10 Mhz 15*15*4 mm 8 Mhz 12*12*4 mm 7 MHz 10*10*4 mm 5 MHz Therefore the smaller the antenna, the more chance it will have that frequency shifts in the device will cause it to perform very poorly, thus necessitating that the antenna bandwidth be retuned to have the effective bandwidth at the GPS 1.5754 GHz frequency.