VLF / Omega

Kritchlow

Kritchlow

Final Approach
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Kritchlow
This is the one form of navigation that I'm not familiar with. I have read about A/N, flown ADF, VOR, Loran, IRS/INS, GPS, and am at least familiar with anything you can throw at me..... other than VLF/Omega.

Is the signal transimitted from the ground? I assume so becaucase of the "VLF" portion can bounce..???
What is the Omega part of the equation?? Is it all one package?? Do they somehow marry up and work together? What exactly is "Omega"? Is it ground transmitted?? Obviously it's not satélites, but INS is pretty old stuff and that's not ground transmitted either.

The young guys here may be lost, but he'll... I'm an old timer and I'm half lost.

I just love the old nastalgic stuff.
 
You timed your question well - in exactly a week we will have the 20th anniversary of the Omega system permanent shutdown.

Kritchlow said:
What exactly is "Omega"? ...Is the signal transmitted from the ground?
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Not is but was. We are taking past tense here. Yes, a number of countries participated to have this almost global aviation/oceanic global navigation system through system of ground antennas/transmitters. The best positional accuracy you could achieve was about 3-4 miles. VLF don't 'bounce', they hug the terrain, can go around mountain ranges, all that by the principle of diffraction. My atomic watch today is also getting 'synced' up using (similar) LF signal (antenna in Fort Collins, Co). Omega receiver was a small suitcase -like box and I bet you needed a trained operator. I think (I could be wrong) Omega was ultimately much more popular on water than in the air.
 
olasek said:
You timed your question well - in exactly a week we will have the 20th anniversary of the Omega system permanent shutdown.


Not is but was. We are taking past tense here. Yes, a number of countries participated to have this almost global aviation/oceanic global navigation system through system of ground antennas/transmitters. The best positional accuracy you could achieve was about 3-4 miles. VLF don't 'bounce', they hug the terrain, can go around mountain ranges, all that by the principle of diffraction. My atomic watch today is also getting 'synced' up using (similar) LF signal (antenna in Fort Collins, Co). Omega receiver was a small suitcase -like box and I bet you needed a trained operator. I think (I could be wrong) Omega was ultimately much more popular on water than in the air.
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Very interesting. I'm still confused by the relationship between VLF and Omega. Were They a cross check on each other like GPS and DME/DME are today?
 
What relationship?? Omega is just a NAME. You could call it "Zeta" if you prefer another letter of Greek alphabet or call it something else. VLF is a frequency range - stands for Very Low Frequency.
 
olasek said:
What relationship?? Omega is just a NAME. You could call it "Zeta" if you prefer another letter of Greek alphabet or call it something else. VLF is a frequency range - stands for Very Low Frequency.
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Okay good.... this is starting to answer some of my questions.
So, "OMEGA" was only a name for VLF?? I always thought it was some sort of auxiliary for VLF... sort of like "VOR/DME" or the like.
Now we're getting somewhere.
 
OMEGA was a name of the whole system (like GPS is a name or LORAN is a name). Omega antennas transmitted their signals in VLF frequency range, around 10-14 Khz. You needed VLF for this purpose or you could not cover the globe, your local radio station transmits in completely different spectrum of radio waves.
 
Kritchlow said:
Ahhh.... thanks Clark. If everything was answered by Google search there would be no need to ask questions, would there?
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In this particular case a google search answered your questions quite efficiently. This was not a matter of everything, only a simple thing.
 
Clark1961 said:
In this particular case a google search answered your questions quite efficiently
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Very true however he seems to had some trouble with concept of frequency range, he could have got lost in the material which is online, but yes, ultimately a good sketch of the history and principles of operation of the Omega system is in such trivial sources like Wikipedia for example (with links to more technical literature).
 
Clark1961 said:
In this particular case a google search answered your questions quite efficiently. This was not a matter of everything, only a simple thing.
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But one never really knows with wiki.

Point is it makes for good chat for the younger folks. They may have never heard of Omega and this thread may have taught them something.
 
I thought it was great back in the 80's when I started using it. We had a Global Series II, no database. Every waypoint was entered using Lat/Long and you had to tell it where it was when you turned it on.

It held 1 flight plan, the active one. 9 waypoints total, waypoint 0 was your current position.

GNS500A_2.jpg
 
Kritchlow said:
This is the one form of navigation that I'm not familiar with. I have read about A/N, flown ADF, VOR, Loran, IRS/INS, GPS, and am at least familiar with anything you can throw at me..... other than VLF/Omega.
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Decca, VAR
 
Kritchlow said:
But one never really knows with wiki anything on-line.

Point is it makes for good chat for the younger folks. They may have never heard of Omega and this thread may have taught them something.
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FTFY. Wikipedia is usually quite good, with the possible exception of currently controversial subjects. Like any on-line source, check any listed references, cross check against other sources. They are usually very good on technical subjects like this one.
 
Plano Pilot said:
It held 1 flight plan, the active one. 9 waypoints total, waypoint 0 was your current position.
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Oh, thanks for posting this, looks like aviation unit, I wasn't sure to what extent it was used in aviation. I am curious what type of aircraft was it installed on?
I agree with the original poster - this is a good discussion to have - specially in view of the 20th anniversary of the demise of the system.
 
VLF jogged a memory. Years ago there was a 60 Minutes episode about Submarine communications. I think the episode was about the antennae were causing cancer, making people crazy, dogs not f***ing or something. Googling don't say nuthin bout that but it is used for communicating with submerged submarines. It can and has been used for ship and airplane navigation. Dont know about OMEGA.
 
Flew with VLF/Omega long-range nav units in DC8s in the late 1990s. Those units had nav databases so used the Omega with DME/DME to produce a position and the database to work similarly to the more modern FMS units though without the accuracy of IRUs or GPS. It was good enough for enroute and terminal RNAV but not RNAV procedures (SIDs/STARs/Approaches).
 
The ones we had in the Falcon 10 (mid-90s) didn't have DME/DME positioning...and the VLF would lose position quite regularly. We were glad to change them out for the KLN-900.
 
olasek said:
Oh, thanks for posting this, looks like aviation unit, I wasn't sure to what extent it was used in aviation. I am curious what type of aircraft was it installed on?
I agree with the original poster - this is a good discussion to have - specially in view of the 20th anniversary of the demise of the system.
Click to expand...

I used them in 2 Falcon 20's and a Citation 500 back in the day.

MauleSkinner said:
The ones we had in the Falcon 10 (mid-90s) didn't have DME/DME positioning...and the VLF would lose position quite regularly. We were glad to change them out for the KLN-900.
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The last Falcon 20 I flew we changed it out for a KLN-900 also. Yes the VLF/Omega would go into DR when we were around convective activity. We would then fly over a VOR and hit "position hold", if I remember right, then enter the lat/long of the VOR to update it's location. It got us to Europe and back in the late 80's!

From what I remember the VLF and Omega was separate. What I was told was the submarines used Omega to navigate and talk on under water. I think there was only around 7 stations around the world.
 
I was a submarine officer on fast attacks in the 80s and 90s. Generally VLF referred to comms, Omega was a nav system that used VLF freqs.
VLF is part ground wave and can penetrate seawater a few 10s of feet hence its usability for comms. Data rate is slow, 50 baud, and power requirements are large, both Cutler ME and Annapolis MD used 2 MWatts input power.

Omega was based on hyperbolic lines of position same as all other radionavigation. We did not use it much except as a confirming backup in open ocean nav, but it was indispensable under the ice, but not for nav as you might think. Basicially the only heading reference you have under the ice is inertial navigation, gyros do not work near the N Pole, above 88 N they were useless. To understand why, appreciate that lines of longitude are not really parallel, they converge at the poles. And all a heading is is an angle to a line of longitude.

So submerged under the ice cap, the only heading reference we had was the INS and if we lost that, a not infrequent occurence, our heading ref would have been Omega. Lock the rudder and go long enough to derive a PIM based in successive positions.

I guess money was why Omega was scotched but I always wondered what boat drivers would do if they lost SINS. But maybe the Navy figured global warming is coming, in a few decades it wouldn't matter!


 
hankrausch said:
I guess money was why Omega was scotched but I always wondered what boat drivers would do if they lost SINS. But maybe the Navy figured global warming is coming, in a few decades it wouldn't matter
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From a conspiracy theory standpoint, it is probably cheaper for the government/Illuminati to melt the polar ice cap than to maintain VLF navigation facilities.

Cool story though. Can you explain more about the gyro problems near the pole? Do the gyros actually stop working for some reason or is it just that they have to be corrected too often to be useful as your longitude changes to account for the increased convergence of the longitude lines? (My guess is the latter, but why not just program the navigation computer to correct for longitude anyhow?)
 
Say you are at 89 N, 100 W and want to steer 045 T. You set the gyro so that you point the boat at 045 T and head off. But as you go, in a straight line, and you cross 99 W, you will not be steering 045 T. You will be steering something to the S of that, say 050. But actually your helmsman will keep the boat at 045 and in reality you will spiral in towards the N pole, he will keep crabbing to the left.

Navigation computer: there is none. Just men with plotters. The closest might be SINS, which always worked. Except when it didn't.

I read your your question again and I think I understand the kernel of it, when you said "is it just they have to corrected so often". There is no external reference ti correct them to.
 
hankrausch said:
Say you are at 89 N, 100 W and want to steer 045 T. You set the gyro so that you point the boat at 045 T and head off. But as you go, in a straight line, and you cross 99 W, you will not be steering 045 T. You will be steering something to the S of that, say 050. But actually your helmsman will keep the boat at 045 and in reality you will spiral in towards the N pole, he will keep crabbing to the left.

Navigation computer: there is none. Just men with plotters. The closest might be SINS, which always worked. Except when it didn't.

I read your your question again and I think I understand the kernel of it, when you said "is it just they have to corrected so often". There is no external reference ti correct them to.
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Yeah, that was the kernel of my question. I had figured that your navigation computer (if my E6-B is a “computer” then a warrant officer and a plotting table should also count as a navigation computer) would be able to correct based on your change in longitude. So when you get to 89 30’ N and 99 30’ W you would know how many degrees off the gyro is and the helmsman could steer right to make up for it.
 
iamtheari said:
Can you explain more about the gyro problems near the pole?
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There are no problems relating to physics of gyros. A typical AHRS or a spinning gyro can't even sense Earth rotation so for them makes absolutely no difference if you are on the equator or at a Pole. Problems are more of a geometrical nature (meridians squashed together) that any active navigation around the poles is not recommended - you keep your wings level and wait till separation of meridians will allow you to engage your autopilot in heading or some other mode. Separation of magnetic and true north presents additional problem.
 
iamtheari said:
Yeah, that was the kernel of my question. I had figured that your navigation computer (if my E6-B is a “computer” then a warrant officer and a plotting table should also count as a navigation computer) would be able to correct based on your change in longitude. So when you get to 89 30’ N and 99 30’ W you would know how many degrees off the gyro is and the helmsman could steer right to make up for it.
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Got it. No we didn't do that. In fact not sure how you could correct for it quantitatively. We just relied on SINS, and if that crapped out had Omega, which is why it was mentioned.
 
luvflyin said:
VLF jogged a memory. Years ago there was a 60 Minutes episode about Submarine communications. I think the episode was about the antennae were causing cancer, making people crazy, dogs not f***ing or something. Googling don't say nuthin bout that but it is used for communicating with submerged submarines. It can and has been used for ship and airplane navigation. Dont know about OMEGA.
Click to expand...

Perhaps it was actually ELF, Extremely Low Frequency.
 
Another old system that we used in 1975 at USAF nav school in the mighty T-29 was CONSOLAN. This was a low frequency transmitter that required only a low frequency radio to use. You could get up to 360 lines of position from the station, based on morse code audio, similar to the way the old A-N ranges worked, except this was not limited to only 4 courses.

We also used LORAN, but our sets required you to use what amounted to an oscilloscope to determine the time delay between the two signals, which you could then obtain a line of position on a Loran chart.

We were also trained for day and night celestial, radar navigation, and use of the drift meter.

I went into fighters and never used that stuff except radar, but it was pretty interesting. A C-130 nav once let me shoot a star shot on his sextant. I think I was only about 500nm off.
 
hankrausch said:
I was a submarine officer on fast attacks in the 80s and 90s. Generally VLF referred to comms, Omega was a nav system that used VLF freqs.
VLF is part ground wave and can penetrate seawater a few 10s of feet hence its usability for comms. Data rate is slow, 50 baud, and power requirements are large, both Cutler ME and Annapolis MD used 2 MWatts input power.

Omega was based on hyperbolic lines of position same as all other radionavigation. We did not use it much except as a confirming backup in open ocean nav, but it was indispensable under the ice, but not for nav as you might think. Basicially the only heading reference you have under the ice is inertial navigation, gyros do not work near the N Pole, above 88 N they were useless. To understand why, appreciate that lines of longitude are not really parallel, they converge at the poles. And all a heading is is an angle to a line of longitude.

So submerged under the ice cap, the only heading reference we had was the INS and if we lost that, a not infrequent occurence, our heading ref would have been Omega. Lock the rudder and go long enough to derive a PIM based in successive positions.

I guess money was why Omega was scotched but I always wondered what boat drivers would do if they lost SINS. But maybe the Navy figured global warming is coming, in a few decades it wouldn't matter!
Click to expand...

Not sure how much power Jim Creek, WA was putting out, but the coils in the transmitter were HUGE. And the antenna, stretching from one side of a canyon to the other, is marked on the SEA Sectional.
 
roncachamp said:
The Project ELF transmitters were in northern Wisconsin and the UP of Michigan. They were periodically targets for sabotage by antiwar protesters.
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Wisconsin was ringing a bell with me when I thought of that 60 minutes episode. Googling VLF didn't turn that up but ELF did. Submarine communications spans both bands FWIW
 
The other fun one I remember was Decca Omnitrak. This was an early moving map (literally, it scrolled a paper map with a bug on it). It used combinations of inputs including LORAN and DECCA's own system. It was a LF based system but used hyperbolic nav (similar to GPS) rathe than the pulse train that LORAN was using. It got very little use other than some transatlantic stuff between the UK and Canada.
 
We had an oddball mission in the Navy that required Omega for an accurate position reference for a rendezvous with a SSBN way far from any sea lanes, where loran reception was iffy and clouds might not allow celestial fixes. We were on a cargo ship, and that is a whole 'nuther story.

The Omega machine had a moving thermal paper output, and it would draw a line across the paper every time we crossed an Omega line of position. Counting the numbers of lines you crossed would give you a current line of position. Since the machine had two receivers in it, by tuning in different stations the lines of positions would cross at your location.

By using this machine on other missions, we determined that Scotland was 1/4 mile away from where it was charted. The beginning point on that trip was Charleston, SC.

Dunno ELF vs VLF. I do remember there were just four transmitting stations world wide, with four (?) more planned. Listening to the raw input you could hear the static caused by every lightening bolt in the world. Somewhere in there was a usable signal.
 
Recognition bias is fun. I read Clancy's 1986 novel "Red Storm Rising" a few years back. The tensions with Russia sparked me to start listening to the audiobook version of it over the weekend. And sure enough, before long there was mention of a frigate crew using Omega and LORAN to navigate.
 
ELF was a different kettle of fish than VLF. It was basically Line Current! Around 47-60 hertz if memory serves. Since the freq was so low, it could penetrate seawater much deeper, hundreds of feet rather than 10s of feet for VLF. But the data rate was much lower, like 3 characters took 5 minutes. It was more of a "bellringer" than a comms system, it was basically used to tell you to come up to comms depth when you were running fast and deep.
 
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