Why don't Submarines use Radio or GPS?

If you have seen almost any old movie that had a submarine in it, you probably saw the crew using radios to communicate with headquarters even when deep underwater. Unfortunately, its not that way in real life. In this video we do a simple experiment with a cell phone to see how radio waves are blocked from it even under under less than an inch of water. And we look at why this happens and how real subs use acoustic, light, and extremely low frequency radio waves to communication with shore.

[@MichaelCowden]

Yet another outstanding and informative video on a fascinating subject. I had understood that this communication was extremely difficult, but didn’t know exactly why or what alternatives existed. Thank you for answering my questions, Dr. Jones!

[@ElectromagneticVideos]

Hi Michael, so glad you enjoyed it! It is fascinating - I remember how interesting it was when I first came across EM waves in a conducting medium as a student. Back then of course there were no cell phones that could easily be dropped in (salt) water so it was all theory.

[@ThriftyToolShed]

Very interesting. I had no idea it was that difficult to transfer data that deep. I do work with many people that were in the Navy and I am sure they knew, but I was not aware. Thanks for sharing!

[@ElectromagneticVideos]

Its hard to imagine when military subs are on longer underwater missions what it must be like to be cut of from all but minimum communications unless they surface. Way back I worked on HF/VHF/UHF communications with IP networking mainly for navy ships. I know subs had the stuff installed presumably for when they surfaced or could at least stick an antenna above the surface. Unfortunately never actually saw our gear on a sub myself.

[@ThriftyToolShed]

@@ElectromagneticVideos That is hard to imagine. Especially as connected as we are today.

[@ElectromagneticVideos]

@@ThriftyToolShed Yeah - it must be so hard.

[@emilalmberg1096]

Thanks for your review, I like your draw and tell technique. Let me tell your viewer about a radio station here in Sweden. (I know you know about it) 100 years ago radio transmissions were established between continents, this was before transistors or even tubes! Everything is mechanical and they transmit at 17.2kHz. This transmitter remains today and is on the Unesco World Heritage List. The reason it survived is that the army always wanted a transmitter to communicate with submarines, this was of course secret in the past, especially during the cold war. The transmitter reaches all over the world and not only Swedish submarines were intended recipients of the signals... Anyone who visits Sweden and has the slightest technical interest should visit this very interesting and beautiful place!

[@ElectromagneticVideos]

Thanks! I believe your referring to the Grimeton Radio Station grimeton.org/en/ which uses an Alexanderson Alternator to produce the 17.2kHz carrier. Ernst Frederick Werner Alexanderson was a Swedish engineer who invented the Alexanderson Alternator as a result of Canadian Reginald Fessenden's request for such a device to allow him to modulate a stable carrier frequency with voice. On Christmas Eve 1906 Fessenden did the first AM radio broadcast ever from Brant Rock, Massachusetts using an alternator from Alexanderson so together these two pioneers invented AM radio and radio broadcasting. Today was en.wikipedia.org/wiki/Alexanderson_Day . Some time I want to be at the Grimeton Radio Station on Alexanderson Day to see the system running and receive its transmissions. Actually I should try and receive it here next year! @emilalmberg1096 has a video here including receiving the signal kzbin.info/www/bejne/eWXae6NsYpadaaM (all in Swedish but even without understanding the commentary its easy to figure out what being shown). Well worth a look!

[@emilalmberg1096]

@@ElectromagneticVideos Thanks, how could I forget the name!

[@ElectromagneticVideos]

@@emilalmberg1096 I'm glad you brought it up - I will now remember that Alexanderson Day is the beginning of August and keep that in mind for a future trip.

[@bulbx1273]

I already know ocean is a bad mirror, no need to put my phone underwater ! thanks for the very clear explanation !

[@ElectromagneticVideos]

Thanks! What didn't point out is how the waves make the reflections even more complicated and random. Creates a lot of clutter for radar.

[@bulbx1273]

@@ElectromagneticVideos can you make a quick video to explain light reflection in a mirror please ? With math equations...

[@ElectromagneticVideos]

@@bulbx1273 That on the way actually. Hopefully with a demo using microwaves on a real mirror so we can visualize the interference patterns from the reflected waves

[@bulbx1273]

@@ElectromagneticVideos Nice ! Thank you !

[@RadioJonophone]

During the 1950s my uncle worked on just this problem. He was a civilian attached to the Royal Navy in Malta. He told me about his work, but said it was all top secret so could not talk about frequencies and powers. That let the cat out of the bag for me as then I knew it was radio communication. I also knew that seawater was a radio muffler, so deduced that the frequency would have to be very low, and that the aerials for transmission (I assumed they were under the surface) would have to be measured in miles. My uncle was awarded an MBE for his work. Many years later, after his death, my cousin came across some rough workings that he made. It seemed he was working on a frequency of 68Hz which would be a wavelength of around 4 million metres in air. His notes suggested an underwater wavelength of around 56Km, so using a quarter wave transmitting aerial that would be 14Km. There was no suggestion as to how much power would be needed to push such a signal a useable distance, but it would have to be in the hundreds of kilowatts, I should imagine.

[@ElectromagneticVideos]

What a wonderful bit of personal history! Nothing as intriguing as "Top Secret" to make you want figure out what he was doing. Its so interesting to hear the frequency he used and how similar it is to what is used today. I guess Maxwell Equations haven't changed :) It must have been such cutting edge work at the time. You and or your cousin telling the story and the old papers would be a great historic video for your channel - I would sure the thrilled to watch it!

[@RichardKCollins]

When I was working with gravimeter arrays about 20 years ago, I found it possible to use the vector sun moon tidal gravity signal to solve for position and orientation of the instrument using gravity. Which is not attenuated by the ionosphere or a conducting ocean, magma or intervening matter. I called it "gravitational GPS" and "gravitational compass". It is possible to use MEMS gravimeters for that now or atom interferometer chips, or several other kinds of detectors. I found more than a dozen low cost ways. As for communication using gravity. When I met Joe Weber at UMD back in the late 1970s, I asked him what he hoped for. He said that his gravitational detectors were intended for communication using 3D time of flight field interferometry. ( He did not say those words exactly, but that is how I would describe 45 years later). But he advised me not to follow him. Rather to follow his student collaborator, Robert Forward whose dissertation is titled "Detectors for Dynamic Gravitational Fields" Now i think Robert was partially responsible for LIGO but I never really bothered to check. I did not meet him until many years later, just before he died. Also, after many decades they now have high dielectric constant antennas that can synthesize and detect low frequencies so you do not need those giant transmitters, and it can be two way. The wavelengths, (using those kinds of transceivers or using array methods) that are larger than the earth would be great for scanning the early universe. From nanoHertz to GigaHertz. Putting low cost arrays on the Moon and Mars, can be as simple as setting them around and letting them self calibrate. Someone wrote me a few months ago about a small sensitive gravity gradiometer that could be adapted for drones and for orbit. An Earth Mars Moon baseline works for gravity too since the speed of light and gravity are identical. Not close, identical -- sharing the same underlying potential. I want to focus them on the sun. The gravity arrays can 3D image the interior of the sun and Moon and Earth. Lots of things that are possible, and not that difficult. But who has time? Add $Thanks and I can buy you a cup of coffee or tea. Richard Collins ,The Internet Foundation

[@ElectromagneticVideos]

Wow - that's really fascinating! So to make sure I understand, are you saying that by measuring the time varying the gravitational field over a period of time at some location, and by knowing the calculated positions of the sun and moon over that time period, you are able to compute your 3D position and orientation in and above the earth? If I got that right, how long a time do you need for the measurement and what type of positional accuracy do you get? I presume the accuracy depends on the time period over which the measurement is made and the sensitivity and noise of instrument?

[@cyndicorinne]

What a great experiment! I always wondered the same thing; movie and books often fake their way through with artistic license and used to make me question my own common sense when younger. Your straightforward experiment settles it, for anyone at any age. 🙏

[@ElectromagneticVideos]

Thanks! Well I think movies are a lot more fun that way. Just like explosions in space apparently can be heard in nearby spaceships :) Your right - an experiment for any age - the simplest experiments are the best!

[@cyndicorinne]

@@ElectromagneticVideos haha I love the reference to explosions in space! (Explosions in Outer Spaaace!) 😂 I guess growing up on Asteroids, Galaxian and Galaga added to my childhood misinformation hahaha! But I loved the games and still to this day can do quite well on them!

[@cokdnlokd1238]

SINS gear started in about 61 my father went under the icepack using that. Submarines have always relied mostly on dead reckoning and Sonar. I am a Merchant marine Master and teach navigation and dynamic positioning which uses ALL available means of positioning.

[@ElectromagneticVideos]

I remember reading an old National Geographic as a kid about a sub going under the icepack. He must have some stories to tell! Since your an expert on the topic, I'm guessing with modern sonar dead reckoning can be pretty accurate? I would think these days they have some sort of automatic dead reckoning where computers automatically track the sonar images to continuously compute and update position? And presumably with absolute corrections based on known underwater landmarks?

[@cokdnlokd1238]

@@ElectromagneticVideos I would not call myself and expert on the subject of US Sub nav as its likely still some classified stuff, but I know that 360 deg charting was done and the movement of the icepack is known and predicted thus the overhead terrain and the ocean floor should allow for fairly precise navigating. Automatic dead reckoning would be somewhat related to SINS (Ships Inertial Navigation Systems) which plots/records movement in all directions. INS is also used to prevent trigger events caused by temporary losses of DGNSS and Hydro-Acoustic positioning data.

[@ElectromagneticVideos]

@@cokdnlokd1238 Yes - I'm sure a lot is classified. With you knowledge of navigation though, I'm sure you can make better guesses as to how they do it than most of us! Question about SINS: I know by its nature INS systems drift over time. Do shipboard ones automatically get corrected by GNSS? Or is the idea to be an independent system of GNSS so one is not relying in GNSS in case of things like GNSS spoofing?

[@Brooke95482]

One of the receiving antennas on a sub is what amounts to an iron core loop. Note that as the depth increases so does both the attenuation of the signal and the attenuation of the noise. That's to say the s/n radio does not change that much. The reason for the locating Clam Lake transmitter on dry soil is so that the antenna is effectively higher above the conducting ground. Ideally the antenna would be 1/4 to 1/2 half wave above a conducting ground.

[@ElectromagneticVideos]

Thanks for posting that interesting bit of information! So is the loop dragged behind it? Or is it effectively a circle around the sub as if the sub was a giant ferrite rod antenna? Or some other configuration?

[@scottthomas3792]

I remember reading an article some years ago about vlf sub communication and I got the impression the antenna of the land based transmitter was submerged... That, and that they really cranked out the wattage. Sort of related. At a local aquarium, there was a display where a pickup coil was connected to an amplifier, in a tank of fish that communicated with electric fields. It sounded almost exactly like dialup...

[@ElectromagneticVideos]

From what I have read, the transmitter antenna is usually kept away from water - the presence of water would greatly increase the amount of current drawn and I would have thought also increase the amount of power wasted. But - it may also provide a better impedance match. So maybe that was the submerged approach you read about. I suspect a lot of the actual implementation details are classified so so who knows what they may have found out to be best. Interesting about the aquarium - that would be fascinating to hear. In the case of fish is essentially near fields (ie non -propagating) that are used. The closest that I have seen to what you describe is voltmeters on an electric eel tank. Unfortunately I guess the eels has no interest in showing off their electric abilities when I visited. Do you remember which aquarium it was?

[@scottthomas3792]

@@ElectromagneticVideos The Newport Aquarium in northern Kentucky. It had just opened, so this was in the early 2000s, I think.

[@ElectromagneticVideos]

@@scottthomas3792 So brand new - that's probably why they had such a neat exhibit. If I'm ever in that area I definitely have to go and see! Thanks for letting me know!

[@Mr.Robert1]

Toothed whales and dolphins (for example killer whales and bottle-nose dolphins) use echolocation for hunting and navigating, while baleen whales (for example humpbacks and blue whales) generally produce a series of sounds which are frequently termed 'songs' that are used for communicating.

[@ElectromagneticVideos]

I had heard that they use lower frequencies for long range singing/communicating and the noise from things like ship propellers was disrupting that. Any idea if that's true and what the consequences to them are? Sounds like you have a bit expertise in that area?

[@debnath5110]

Beautiful presentation...Thank you Sir....

[@ElectromagneticVideos]

That you so much! Glad you liked it!

[@azimuth4850]

Very good explanation!

[@ElectromagneticVideos]

Thank you!!!!!!

[@luckydubeinrc5165]

subs trail long wires behind them for radio comms, ok it was long ago but they did do low wave comms

[@ElectromagneticVideos]

low wave? did you mean/autocorrect long wave?The waves of of ELF frequencies in air are much longer than what is normally referred to as long wave. - ELF 100Hz for example produces 3km waves (shorter but still very long in water). That's the reason for the trailing antenna wire.

[@maverick627uk]

Excellent explanation. I understood the fact that radio couldn't penetrate the water without major issues which you addressed, but the details I was very rusty on. I'll definitely be doing some refreshing my knowledge and learning some new topics from your videos. Great job 👍

[@ElectromagneticVideos]

Thank you so much! I'm thrilled your enjoying my videos. From your name you must be in the UK - greetings from Canada!

[@maverick627uk]

@@ElectromagneticVideos Yes, greetings from the UK. I was watching the speed of light video. Unfortunately due to lack of equipment, I used 2 green laser pointers and 2 way radios. I measured the speed of light at 27mph so im guessing did something wrong 😀. No but seriously, its interesting because technically we can only measure twice the speed of light because we need the return signal to take the measurement. I think it was Veritasium who did a video about it. Thanks again, great explanations 🏴󠁧󠁢󠁥󠁮󠁧󠁿👍

[@bobbing4snapples]

I learn so much from you. Thank you.

[@ElectromagneticVideos]

Thank you so much for that! I have always found this type of stuff so interesting ever since I first came across it as a student. More to come!

[@ChrisM-qi2qi]

Finally a You-Tuber who is not afraid to say "miles" ! Too many just refuse nowadays and only say kilometers and it irritates the heck out of me when watching science videos.

[@ElectromagneticVideos]

You wouldn't believe the number of comments I got on the "speed of light" video where I used feet because of the so convenient "1 foot per ns" speed of light.

[@jonahansen]

This is also why it is difficult to employ hi-frequency radio to gather data from electronic devices in the body, like ingestible or implanted monitors or defibrillators. It's still possible though, because RF techniques can be used to extract even tiny signals, and inside a body you only have like 10 cm of "saltwater" surrounding the device, plus it's only 1/3 as salty as the ocean. But submarines are thousands of meters under water in many cases. I think in "Crimson Tide" they have scenes where they have to raise an antenna in order to communicate. They also use very low frequencies such as 20 kHz that need huge antennas...

[@ElectromagneticVideos]

I never thought of the link between this and the human body. I immediately think of Cochlear implants- I'm pretty sure they use coils near the skin - maybe so its more near field magnetic coupling than EM waves. And I guess those RFID implants for dogs (and probably Twitter employees these days:) are so near the surface the attenuation is and amount of salty tissue is minimal. I think the raising the antenna bit was/is pretty common if one is sure the enemy isnt nearby. Years ago I was in involved in HF comms equipment that was deployed in various places including subs, and that what I assumed they did but unfortunately never got to see a sub equipped with the equipment.

[@Lucas-up6ww]

One ping only.

[@ElectromagneticVideos]

What an iconic scene that was!

[@Harley.Davidson]

That us a classic scene!

[@ElectromagneticVideos]

@@Harley.Davidson One of the most classic ever!

[@Mr.Robert1]

Mr vasili

[@ElectromagneticVideos]

@@Mr.Robert1 So I'm stumped - are you referring to en.wikipedia.org/wiki/Vasily_Arkhipov ?

[@LarsLarsen77]

Subs absolutely do use radio. They tow really long antenna wires behind them and transmit VLF data messages.

[@retrozmachine1189]

Are you referring to VLF? That's not shortwave by any extreme of the meaning. We are talking wavelengths of in excess of 10km. Even then this is not deep ocean stuff, you have to be within cooee of the surface still. Go down to the sort of depths these amateurs were trying and you won't hear a peep on VLF.

[@ElectromagneticVideos]

Thanks for responding - I think the original commenter changed to host to VLF after reading your comment. I do wonder how deep ELF works - I'm guessing that very classified.

[@dannelson8556]

omg the fact that you have to explain this demonstrates the dumbing down of the gene pool. I understood this back in the '60s when I was just a kid of course I was a ham radio operator. By the way submarines can use long wave RF communications.

[@ElectromagneticVideos]

I'm not quite as pessimistic as you! As obvious as skin depth effects are to you and me, its not something that is covered in High School science, and many movies make people think underwater comms is easy!

[@neilsheldon8355]

Loved the video ... I'm an old timer submarine sailor, whose boat doesn't exist any more (decommissioned), and was considered old technology at that time. (WWII Diesel Boat), so our technology and tactics were pretty different from modern boats. But, I don't remember hearing about a sunken sub from US since the late 60's / early 70's (Scorpion). Was that from a different country?

[@ElectromagneticVideos]

Thanks so much - really means something coming from an actual submarine sailor. You are way braver than me to have done that! I quickly through together this video in June 2023 after the private so-called-experimental sub Titan from OceanGate Inc imploded while descending to the Titanic. There were numerous comments along the lines of "why didnt it have a GPS onboard" and "why did they use a radio to call for help" under the articles covering the search and rescue attempts. People just dont understand that radio communications (and GPS) dont work well while underwater. The last military sub that sunk that I heard of was an Argentinian sub ARA San Juan in 2017. Terrible to think of all the lives that were lost. What was your job on the sub? Did you enjoy it or is life on a sub pretty thankless experience? I have visited the two vintage subs at the Marine Museum in San Diego (US and Soviet). So small inside!

[@neilsheldon8355]

@@ElectromagneticVideos I believe that many of the old decommissioned subs were sold to other nations. So, that Argentinian sub may have originally been one of ours. It is always sad to hear when a sub goes down, and having been abord one for some time, regardless of nationality, there is still a certain sadness that, I think, all sub sailors feel that sadness for those lost. I had many jobs at one time or another, and, although I made 3rd Class Radioman when I was aboard, I never got to exercise that skill until after the sub was decommissioned, and I was transferred to a communications center in Pearl Harbor. But while I was there, I was initially a lookout/helmsman/Bow/Stern Plane operator. Later I worked with the Engineman gang, and stood watches in the engine room, and as part of that duty, when submerged (typically when the engines were not running) I stood watch at the trim and drain manifold. And last but not least, all the newer men get to do a stint as mess cook, where we do dishes, and during off hours we would set up something like a self serve snack bar for those just going on watch and those just coming off watch. In my duties at the communications center, I would run teletype broadcasts, changing out messages on specific schedules. Later I was privileged to set up the crypto gear with new keys for their specific periods. (all that stuff is declassified these days). During my shore duty, we were also required to put in two days at sea each month to maintain our submarine skills. I was fortunate to be able to ride several submarines (most all of them decommissioned as far as I know, now.) One of them happens to be on display in Portland Oregon at the OMSI (Museum). It was one of the last diesel boats. The diesel boat that I was on was very much like the one at Fisherman's Warf in San Francisco. I think that one is the USS Pampanito. They have a pretty good website if you care to visit. The last sub I visited was the USS Batfish. It is now located in Muskogee, OK believe it or not. Pretty cool story about how that happened. I think they have a web site too.

[@ElectromagneticVideos]

@@neilsheldon8355 What an interesting background and career!. I'll bet you right abut the Argentinian sub - nit viable for most places to order brand new ones. Those disasters are so sad. In your radioman days, did you ever use wsc-3 transceivers? About twenty years ago a company I was with developed modems and IP networking that operated over those transceivers where were 20 or 30 years old. I think some subs even got outfitted with our stuff. We also interfaced though a crypto - cant think of the model number right now.

[@neilsheldon8355]

@@ElectromagneticVideos I was in the service over 50 years ago :) ... so you're talking about new technology compared to what I knew about.

[@flaviocorretordeimoveis-pr8476]

Great video! the thinkness that have entry in my mind when I was listering you saying use ultrasonic instead eletromagnetic waves is the use for short link between electronics devices near each other instead eletromagnetic waves, probabily it already exist, if it not, why not? what is the practical limitation for these application

[@ElectromagneticVideos]

Thanks! I suspect the ultrasonic data rate in water is limited by the bandwidth of ultrasonic loudspeaker and microphone. I have never worked with those things underwater so I'm not sure what the actual data rate limits are even at close distance, but my guess is you cant easily get anywhere near the 10s of Mhz needed for 100s of Mbits/s we are so used to these days. I would think using a blue laser is the way to achieve the data rates we are more used to underwater since since there would be nothing limiting the modulation bandwidth.

[@flaviocorretordeimoveis-pr8476]

@@ElectromagneticVideos thanks!

[@ElectromagneticVideos]

@@flaviocorretordeimoveis-pr8476 Your welcome!

[@cyndicorinne]

3:26 cellphone tower 🤦‍♀️ lol 😝 (It’s true though lol)

[@ElectromagneticVideos]

These days cellphone antennas seem to be on every tower they can find!

[@cyndicorinne]

@@ElectromagneticVideos yep, I’ve seen them disguised as trees down here in Louisiana.

[@ElectromagneticVideos]

@@cyndicorinne I have seen photos of that. Not the greatest disguise but better than the plain tower.

[@cyndicorinne]

@@ElectromagneticVideos 😁 yeah I thought it was kind of cheesy and funny- if done right it probably is good to keep it looking nicer in the city!

[@obagbemisoyejoseph212]

What about Sonar emitted and receiver.

[@ElectromagneticVideos]

I mention that towards the end of the video under acoustic and ultrasonic communications. The sub that sunk used an acoustic or ultrasonic modem for communications with the surface. The issue is for communications of any range such as from the titanic to the surface, the date rates are really low. Apparently they had to keep text messages short because of that.

[@guyonabuffalo100]

I know nothing about this, but i love to broaden my knowledge.

[@ElectromagneticVideos]

Glad it did that! I'm always amazed at things I find on KZbin that teach me one things or another!

[@robertparenton7470]

Will a high-power laser beam reach the surface at 800 - 13,000 ft? If Ocean Gate had such a laser, maybe it could have been found sooner.

[@ElectromagneticVideos]

You know, I don't know what the attenuation of blue light is in seawater since thats the color that you would use since it is absorbed the least. I have suba dived to 100 feet in the great lakes and on a bright sunny day its pretty dark at 100 feet so a lot of even blue light is lost to absorption. Same would apply to the laser. Make it powerful enough and you could probably get it to work, but it might need to be so strong it would cook any fish that happened to swim into it. It would also spread out by the time it gets to the surface due to scatting from the various particles in the water, maybe making a faint glow on the surface. For military applications, if the enemy knew the laser wavelength, they could use a very narrow band filter on a satellite camera to look for that laser light and detect the glow and hence the location of a sub. So not good for military at depth but maybe for search and rescue assuming the laser can be kept to a reasonable size.

[@cokdnlokd1238]

American submarines use ELF radio and towed GNSS buoys so for sure they do.

[@ElectromagneticVideos]

So do you know how often they tow GNSS buoys? Do they use something like inertial navigation between exact positions obtained from GNSS ?

[@johncantwell8216]

Subs have been using inertial navigation since the 1960's. One of my former co-workers was employed by Sperry Gyroscope at that time, and he was involved with sea trials for these systems. He told me that they had to come up to navigation periscope depth on a periodic basis to obtain position fixes from star trackers and sun trackers. Before the days of widespread satellite navigation, although the Navy was developing these systems at the time.@@ElectromagneticVideos

[@terjeoseberg990]

What about submarine to submarine transmission?

[@ElectromagneticVideos]

Assuming you mean while submerged, like sub to shore comms, radio would face the same limitations. Transmitting Extremely Low Frequency RF (ELF) from a sub is probably not feasible due to the need for high power levels and antennas many miles long. If close to the surface such that an antenna could be raised from a buoy or periscope, HF, VHF ,or UHF radio could be used. At depth, acoustic/ultrasonic modems like those used for sub to surface comms with similar speed vs distance tradeoffs so the subs would have to be near enough each other to be able to hear each other. Probably a few miles type range. Or for much higher data rates, blue laser type communications would work but they would also have to be relatively close and know approximately where each other was to point to the laser. Having said all of this, I don't know know if they actually try to communicate sub to sub underwater, or if its all sub to shore with shore relaying communications if needed. If anyone knows and it isn't classified, please post !

[@reccocon3442]

How about earth to space communications. Obviously much less that hinders communications then underseas. The time delays from the transmission to the reciver -say, from whether upper stratosphere to the moon, Mars, pluto and back? Just sub'd. Thank you the education, enjoy & learning even relearning some basics. Appreciate your tutorials !

[@ElectromagneticVideos]

@@reccocon3442 Space is interesting for the very reasons you mentioned: the long delays. That essentially means real-time feedback to re-transmit a failed packet is not practical (something we do all the time on the internet with things like TCP/IP). The other is issue the huge distances which results in extreme signal power loss so the signal to noise ratio goes way down even if the noise is small. In the analog days very very wideband FM was used for modulation - wider swing of frequencies for FM modulation can be used to transmit in situations with signal well below the noise. Today its digital error correction encoding that is used. Even very short scale transmissions are subject to the this such as internet via geosynchronous orbit satellites. The time to send a signal to a satellite is 0.25 sec. So browser->sat->server->sat->browser takes about a second. With todays web pages with many embedded layers mean many round trip times = seconds to load any page (I know - 16 years ago I had internet via Hughsnet satellite - slow!) . Almost unacceptable these days - systems like starlink use low earth orbit satellites with negligible days so they are way better. Glad you subscribed - more stuff to come soon ...

[@johncantwell8216]

For deeply submerged subs a long distance from the coastal VLF/ELF facilities, they use a modified Boeing 707 trailing a 2-component antenna system with cables thousands of feet long. They fly tight circles to relay messages to subs "on station". I've heard that the transmitter has an output of about 200 kW, limited somewhat by the capacity of the 707's generators. Obviously, this is an inconvenient way to communicate. @@ElectromagneticVideos

[@ElectromagneticVideos]

@@johncantwell8216 That is fascinating! I had never heard of VLF/ELF done from the air. Hard to imagine what it must have been like for the pilots flying a plane dragging something like that. And the electronics on board to hand those powers at low frequency must have been massive. Thanks for posting - that's the coolest way of communicating at VLF/ELF that I have ever heard of!

[@DanBeauvoir-uo7yc]

everything was fun and giggles untill the math came up out of nowhere..

[@ElectromagneticVideos]

Oops! I guess I should have never mentioned math :)

[@SuburbanDon]

I thought submarines used VLF ?

[@ElectromagneticVideos]

Yes! Military subs do : kzbin.info/www/bejne/mYHbioyte85-Zs0si=Zn_JEbXGwHXq-hhb&t=852

[@snakezdewiggle6084]

You do know the surface of the Ocean / Sea, etc. is fresh water, right !? Many 10's of inches in many places. Here's a better question: How do Whales communicate across the greatest distances of the largest Oceans, regardless of the curvature of the Earth or Sea bed ? ;)

[@Harley.Davidson]

Thank you.

[@Mr.Robert1]

They are designed and evolved for that purpose. Not by man. Buy something a little more powerful.

[@snakezdewiggle6084]

@Mr.Robert1 Yes, God made "all the fishes in deep blue sea". And evolution is undeniable. But Submarines hear Whale Song from many Thousands of miles. Even cause Comms blackouts.