Escorts Insane detection (GWX)

[frigokar]

Whats wrong with escorts detection? Is this a bug or intended?

Tried with two diffrent convoys...Lied in wait in front of them, silent running is on (read in a post "way too hard" by fast fed) (also stupid if im staning sumberged,no loading of torpedoes or anything how do they hear me...is my crew banging hammers on the walls when theres nothing to do?)

Anyways both time escorts just come charging at my position pingning and then depth charging...

Its january 1941...

Solution????

[banryu79]

Solution????
In a similar situation I think I will try to stay out of the ASDIC cone of the escorts. If this means NOT to lay in front of the convoy but instead to try an approach from one of the flanks of the convoy... I will go for it!

EDIT:
Also please note that to really be in a "silent running" condition you have to keep your boat engines RPM < 100. You can easly do that specifing directly a speed... for example in a Type VII try with 1 Kt or sligthly less.

[Von Tonner]

Whats wrong with escorts detection? Is this a bug or intended?

Tried with two diffrent convoys...Lied in wait in front of them, silent running is on (read in a post "way too hard" by fast fed) (also stupid if im staning sumberged,no loading of torpedoes or anything how do they hear me...is my crew banging hammers on the walls when theres nothing to do?)

Anyways both time escorts just come charging at my position pingning and then depth charging...

Its january 1941...

Solution????

Silent running is not fail safe. It is simply a precaution. In other words on a scale of 0 to 10 it would probably be around 3 depending on weather conditions etc. It can never be a "0"

What I would do if lying in wait in front of a convoy is go as deep as possible until all lead destroyers have passed overhead. Then, and only then would I come up to periscope depth.

With this approach you can have your boat lie horizontally to the convoy as at depth you are unlikely to be picked up. Or if you really want to play safe and give as little footprint as possible, then bring your boat around as you come up. The big advantage to this manoeuvre is that when you do get to periscope depth all tubes, fore and aft can come into immediate play as you more than likely will be right amongst your targets.

Hope this helps.

[frigokar]

I am not moving or making any noise and escorts still charge at me...dont tell me you play like this and take this as normal game behaviour...i played silent hunter a long time ago...but started playing recently with GWX and 1980x1080 gui mod.Even at late years escorts were not clairvoyant :doh:

Since all the people here suggest always something like dont make noise or maybe they see your periscope on radar ( its 1941 and no my periscope is down)
im assuming this is some kind of bug only happening to some people.

If you stayed 10 km in front of the convoy,submerged at night with some fog and waves,silent running no periscope or any kind of movement,loading and such and a escort comes closing EXACTLY on your position dropping depth charges and pinging...then i guess you would know what im talking about

[Von Tonner]

If you stayed 10 km in front of the convoy,submerged at night with some fog and waves,silent running no periscope or any kind of movement,loading and such

I play GWX and yes, sometimes I stick my periscope up and all I see is a damn destroyer bearing right down on me. Not all the time though.

My question is. What depth are you at when they pick you up? I ask that because as you know - "depth is your friend":up:

[frigokar]

periscope depth...but how are they picking me up...through what appartus?

[Ping Jockey]

GWX changes the Sonar settings in the Sim folder. The stock settings make it to easy to go undetected.:D

[Von Tonner]

periscope depth...but how are they picking me up...through what appartus?

If you are 10 kilometers out there should be no way at all that they could pick you up. The GWX Manuel gives early war sonar range at 1 to 2 kilometers depending on variables.

Some posters are of the opinion that this range has been boosted in GWX. But if you are been picked up 10k's out that is simply amazing. There is no ways you would even be able to get close to a convoy.

[maillemaker]

In 1941 you should have no problem with a frontal-quadrant attack.

My ideal attack pattern is to plot an intercept directly in front of a convoy, then angle my course towards the outside of the convoy. I turn away from the convoy as required to keep my boat at least 1500 meters away from the lead escort. You should be at silent running throughout the approach. This means instructing your engineer to set silent running but also means running no faster than ahead slow. Sometimes, if I am scooting quite close by the lead escort I will even order all stop and coast while he goes by.

If I'm not able to position myself directly in front of the convoy I will try and approach from the side such that I am beside the lead escort but will pass well in front of the lead flank escort. You are basically trying to thread the needle avoiding detection between those two escorts. It is easiest to let the convoy run you over and only have to dodge the lead escort. This can be tricky though as the lead escort often weaves back and forth in front of the convoy. If he happens to be moving towards you while you are trying to slide past him, bad things can happen. :)

Note that this approach obviously only works if the convoy has not already been alerted to your presence through a visual or radar contact. Once they start zig-zagging your will not be able to make a silent approach - they are alerted and they will find you.

Once you get into 1943 it is generally not a good idea to try to get inside the convoy. At that point your only real hope is long range shots from 5000+ meters with pattern-running torpedoes and hope your Hail Mary shots hit something while you dive and avoid detection. You must avoid detection at all costs by that time of the war or you are finished. Also I recommend not making any attack against any target where ASW vessels are within range without having 100% hull integrity so that you can dive to your maximum depth.

Once you get homing torpedoes you can once again get in close to the convoys if you are good enough to pick off the escorts with the magic torpedoes.

Steve

[frigokar]

il try reinstaling everything...maybe try NYGM...alternatively im gonna wait for living sh5...tnx for help but i think this kind of **** doesent happen to you and i hope it doesent...:)

[BigWalleye]

il try reinstaling everything...maybe try NYGM...alternatively im gonna wait for living sh5...tnx for help but i think this kind of **** doesent happen to you and i hope it doesent...:)

Since GWX is the only mod you are using, a complete uninstall, registry cleanup, and reinstall should take maybe 20 minutes. I'd encourage you to also re-download GWX3 before you do the reinstall. All told, you will invest less time than continuing to try and pin down the problem. Why fight it?

[UKönig]

Here is some technical information about the type VIIC (sound profiles) from U-boat archive.net, enjoy!

Page 24
A. Ship Information
U-Boat Type VIIC

24
I. General
U-boat Information

h) Sound levels (from testing with "U-45 and "U-51")
(updated for VII C boats after testing)

Boat lying on the bottom
Sound from auxiliary machinery at 250 meters distance
Operating: Underwater telegraphy converter and gyro compass

Not heard
Gyro compass-circulation pump
Gyro compass- converter
Extending attack periscope
Extending air search periscope
Tracking motor in torpedo data computer
Dive planes electric drive
Dive planes (hand drive)
Main rudder electric drive
Quiet
Radio converter
Hydraulic oil pump
W.C. pump
Echolot (shallow depth device)
Control valves for the periscope drive
Engine order telegraph without buzzer
Main rudder (hand drive)
Moderately loud
UT converter
Auxiliary LO pump
Retracting attack periscope
Retracting air search periscope
Compartment ventilation fan
Engine order telegraph with buzzer
Loud
Main drain pump
Walking in the boat
Very loud
Auxiliary drain and trim pump
Air compressor
Drive motor for turning attack periscope
Speaking in the boat
Working in the boat
Echolot (deep depth device)

Boat hanging on the periscope

Sound from auxiliary machinery at 250 meters distance. Motors stopped. No auxiliary machinery except for UT converter and gyro compass.

Not heard
Extending air search periscope
Extending attack periscope
Moderately loud
Retracting air search periscope
Retracting attack periscope

Boat at attack depth
Boat driven at attack depth in a circle of 500 meters radius
Not heard
One motor KF = 50 RPM
Attack periscope
Dive plane driving motor
Both motors KF = 50 RPM
Compartment ventilating fan
Both dive plane driving motors
Quiet
Draining and trimming with air
Operating both dive planes by hand
Both motors 80 RPM
Loud
Draining and trimming with auxiliary drain and trim pump
Both motors 140 RPM
Both motors 120 RPM
Both motors LF 100 RPM
Very loud
Both motors 250 RPM
Both motors 200 RPM
Both motors 180 RPM
Both motors 160 RPM
At starboard 110 and port 90 RPM the noise is weaker than with both motors at 100 RPM
Draining and trimming by means of air at 80 RPM or less: slight noise is audible.
Detection range with different RPM rates (submerged)
At 80 RPM: 4500 meters (Detection range particularly large because of howling sound)
At 160 RPM: 5000 meters (Detection range lowered.)

From the U-boat owner's manual, about as official as it gets...

[banryu79]

Kudos to you UKönig! :)
Thanks for the awsome info!

So it looks like GWX is not hitting us with random stuff... very intresting :hmmm:

This means the game probably requires a high degree of attention, care and situational awarness (and a bit of experience) from each wannabe kaleun who would try to put his feet in this kind of simulated shoes...

[BigWalleye]

Kudos to you UKönig! :)
Thanks for the awsome info!

So it looks like GWX is not hitting us with random stuff... very intresting :hmmm:

This means the game probably requires a high degree of attention, care and situational awarness (and a bit of experience) from each wannabe kaleun who would try to put his feet in this kind of simulated shoes...

That is always presuming that GWX accurately models these sound profiles. And that the SH3 game engine actually is flexible enough and precise enough to permit such modeling. I don't know if either of these is true, but I'll bet there are people around this forum who do.

Otherwise, it comes down to individual experience to ascertain what is really going on in the game (as opposed to what was true R/L).

For example, UKönig's post basically says that running slow (80 rpm) doesn't significantly lower detection range compared to running about Ahead One-Third (160 rpm). Is this borne out by experience?

Detection range with different RPM rates (submerged)
At 80 RPM: 4500 meters (Detection range particularly large because of howling sound)
At 160 RPM: 5000 meters (Detection range lowered.)Other examples: I have seen posts indicating that, in the game, the Echolot is never heard by the enemy, and this is borne out by my own experience. In R/L, raising a scope does not produce any noise, but lowering one does. I haven't noticed such behavior, but it might be present in-game.

Most of the activites classed as "Loud" or "Very Loud" are prevented when in Silent Running. But turning the attack periscope is allowed, and, AFAIK, does not increase detection probability.

We are more fortunate than our R/L prototypes, because we can learn from all of our experiences, successful or not. They only learned from the ones that didn't get them killed.

In the end, the model is what the model is, and it is not a U-boat.

[sublynx]

Some suggestions:

re-install just in case you have detection range settings corrupted

after that:

try

1. waiting for bad weather
2. keeping a distance of 2000 meters to the escorts
3. minimizing up periscope time
4. running at 50 RPM
5. occasionally switching off engines altogether
6. keeping your bow turned towards the closest escort

Don't get frustrated by a failed approach, take notes about the situation instead and try something new on the next attempt

The approach will get more and more difficult by the years, so:

7. Start learning how to shoot from a minimum distance of 4500 - 5000 meters

[UKönig]

To be fair, I am trying to recreate the page the info was found on, and it was from the original german type viic technical manual. I don't know how to read some of the charts or mathematical formulas involved. And some of the equipment that makes noise in one state seems to make more or less noise in another state. I presented it here for the reader to try to interpret his own understanding on the document.
I am learning everything that I can about the subject, and I will play the game based on those rules. If the game falls short, I will realize it (and start 'gaming the game'), and carry on as I know something that it doesn't.
Besides, I've said here and elsewhere, I have an unhealthy devotion to the subject matter, and I'm sure that a lot of other readers/players here do as well.
I know where I can get more of this "submarine-porn" :)

[Pisces]

Something that is not yet mentioned [whoops, missed sublynx' point 6] is your orientation to the incomming destroyers as they are pinging. You return a much stronger signal when you are pointed perpendicular to the direction to the pinging warship. Don't give them your flank, but try to line up with them making your reflective surface as small as possible.

Roughly speaking, when the destroyer is on the 330 or 030 bearing then you are still showing halve of your maximum reflective surface when showing your broadside.

[BigWalleye]

Something that is not yet mentioned [whoops, missed sublynx' point 6] is your orientation to the incomming destroyers as they are pinging. You return a much stronger signal when you are pointed perpendicular to the direction to the pinging warship. Don't give them your flank, but try to line up with them making your reflective surface as small as possible.

Roughly speaking, when the destroyer is on the 330 or 030 bearing then you are still showing halve of your maximum reflective surface when showing your broadside.

Another factor that hasn't been mentioned was the tactic of lead escorts pinging "on spec". I know from first-person accounts that the IJN, at least, used this tactic, and I have seen it used in SH4. I don't know if it was part of UK/Us ASW doctrine. But the purpose was to force the prudent sub commander to take evasive action to avoid being caught in the search cone. Hopefully, this would cause subs lying in ambush positions on-track to miss their attack opportunity.

[banryu79]

Another factor that hasn't been mentioned was the tactic of lead escorts pinging "on spec".
Please, could you direct me (and any intrested reader) to a source that explains and/or discuss this asw tactic? Or maybe expand your own explanation, if it a simple enough thing to be explained in a post on a forum!

I will appreciate it very much :)

[BigWalleye]

Please, could you direct me (and any intrested reader) to a source that explains and/or discuss this asw tactic? Or maybe expand your own explanation, if it a simple enough thing to be explained in a post on a forum!

I will appreciate it very much :)

Sorry, didn't mean to be obscure. Means "on speculation." The lead escort would ping continually, without any prior hydrophone contact. As I said, the idea was to cause any sub lying in ambush near the track to evade in one or the other dimension before the escort closed to sonar contact range. Presumably, the sub so flushed would be unable to get back to a favorable attack position before the convoy had moved past.

[frigokar]

i thought about how these escorts could come charging at my position assuming everything works as intended

Since i used hydrophone to locate the convoy at long range i obviously came in front of it using diesels at surface maintaing long range

1. One of the escorts had radar (both times in different convoys) (in january 1941) and picked me up in semi bad weather and remebered my position once i dived in front of the convoy...(i thought i was safe from escorts radar at least until 1942 and that early radars were very not effective against uboats)

2. Always thought that they cant, but can a escort hear you on its hydrophone if you are on the surface? Then again like radar it remebered my position once i dived and came charging at me

EDIT: It was night in both cases with semi bad weather so it couldnt be visual detection

SOME MORE EDIT: Did some research and wikipedia says that prototype radar was first tested at sea in March 1941 and operational units were fitted in august 1941...The Uboats.net page tells that U 100 (sunk in march 1941 captained by Joachim Schepke was the first uboat sunk by being detected by radar (coincedentaly my current Uboat designation ingame thats how i runed into this info :P)

AND SOME MORE EDIT: Just read in a book Churchills Navy by Brian Lavery that "32 sets of Typ268M were fitted by end of 1940...by middle of June 1941 some 200 ships had them but that their wavelenght was not suitable for anti sumbarine warfare,especialy in rough weathers." So i guess i was extremly unlucky to run into two convoys that had radar equiped escorts and that they did manage to detect me in that weather.Talk about chances. But then again dont know how GWX simulates this

[UKönig]

If you are part of an HK unit that has located an underwater U-boat, then you are about to embark on a rewarding experience that will likely end in a kill.
The lead escort ahead covers the forward arc, the sweepers along the side protect the flanks and the one "walking drag" will often mop up.
Later in the war (but not too much later) Hunter-killer groups will tag along some distance behind, but ready to accelerate to 35 knots when the sweeper or drag units have confirmed a U-boat in the area. The HK units will then take over the task of destroying you and your boat so the escorts can continue with the convoy. The hunter killer units have no other job than to make sure that you are dead. No softer fate awaits any boat forced back to the surface either. It's not too easy to surrender. The Tommies want to see red, for there at last is the enemy in front of them, for whom they've been staring themselves blind. Days, weeks, maybe months on end with no peace or calming nerves, the tormentor torturing them, even when he was a hundred miles away. Nobody in convoy can ever be sure that he's not being watched from the trough of some wave by that cyclopean eye. And there she is suddenly, the viper that drew blood. Nobody can blame them really....
If they are good, the enemy captains will take turns. The U-boat will never really know which of the escort units is attacking it. The first captain will hold the boat in ASDIC and radio that information to the attacking ship, which is going too fast to use it's own sets properly. ASDIC is useless at high speed and normal hydrophones are deafened by the water streaming over them. ASDIC detection is not dependent on sound but magnetic anomaly, or, the mass of the U-boat in water. Or part of it is, I'm no expert but the sonic ping and return cannot be concealed by stealth. It's been described by those in the know as stones thrown at the hull. Being quiet will only help you lose contact if you are able to get below the jet stream. The salinity of ocean water hinges on a few things and even stuff like too much plankton can disturb it. The short version is, by diving below thermal/salt layers and going to quiet mode a submarine can make the HE operator lose contact. This is when the HKs will go back to their usual tactic, carpet bombing at random. Maybe if they score a hit, do some damage or make the U-boat make more noise, vis-a-vis damage control, they can start being more accurate again. And an oil slick is unmistakable evidence of a direct hit. Once the blood of the boat has been drawn, the next rule is "Don't stop until the Captain's cap floats up".
This isn't always represented in a game but like I said, I learn the reality and the history behind it and carry on as if. If not, then I don't worry about it, it's just a good habit to get into.

[BigWalleye]

ASDIC detection is not dependent on sound but magnetic anomaly, or, the mass of the U-boat in water.

UKönig, could you please provide a source that explains how ASDIC actually worked. I was always under the impression that it was a form of echolocation, based on reflected sound waves (the way a bat flies at night). I had no idea that it was magnetc in nature. Could you provide any more information? Thanks.

[banryu79]

UKönig, could you please provide a source that explains how ASDIC actually worked. I was always under the impression that it was a form of echolocation, based on reflected sound waves (the way a bat flies at night). I had no idea that it was magnetc in nature. Could you provide any more information? Thanks.
This sounds strange for me too, I already red or believed ASDIC was based on generating sound waves and detecting the echo produced by the hull of the uboat when hit. :06:

Btw, BigWalleye, thanks for your explanation.

[Zosimus]

http://uboat.net/allies/technical/asdic.htm

ASDIC / Sonar

ASDIC was the primary underwater detection device used by Allied escorts throughout the war. The first versions, crude to say the least, were created near the end of World War One and further developed in the following years by the Royal Navy.

How it works
The ASDIC, known to the Americans as Sonar, was basically a transmitter-receiver sending out a highly directional sound wave through the water. If the sound wave struck a submerged object it was reflected back and picked up by the receiver. The length of the time from transmission until the echo was received was used to measure the range, which was shown as a flickering light on the range scale. By mounting the transmitter head so that it could be directed almost like a searchlight, the bearing of the target could be read from the compass receiver.

The transmitter (sound) head extended beneath the ship, and was encased in a large metal done to minimize the noise of the water rushing past the ship while at moderate speed. This dome was filled with water, through which the sound passed, although this water was stationary and acted almost like a bumper. Noise level remained relatively low at moderate speeds, but anything above 18 knots resulted in too much noise and good contacts were difficult to find. The same results also resulted from bad weather when the ships were rolling, pitching and heaving.

The search pattern
During screening operations the ASDIC operator searched through an arc of roughly 45 degrees each side of the base course of the vessel. The ASDIC had to be stopped at regular intervals on this arc long enough to allow the relatively slow underwater sound waves to return should they locate a submerged target. Normally the head would be stopped on a bearing and a sound pulse would be transmitted, which would be heard as a "ping" noise. If no echo was received after several seconds the head would be rotated a few degrees (usually 5) and the process repeated throughout the watch.

If the outgoing impulse stuck a submerged target the echo would be heard as a distinct "beep". If this occurred the ASDIC operator would sound the alarm, feed the range and bearing to the bridge and then immediately start left and right cuts to try to determine the width of the target and trying to see if it was moving from one side to another. He could also determine if the target was closing or opening the range.

Echoes would bounce back from many things besides the U-boats such as whales, schools of fish, vertical sea currents and ship's wakes. This caused many false alarms, especially with the inexperienced operators. The veteran operator was much better at figuring out these bad signals and hunting down the intended target. The commanding officers quickly learned which operators were reliable.

Another problem was that often a real U-boat could not be detected due to water conditions. ASDIC was not very reliable in rough water, nor when layers of different temperature deflected the sound waves. U-boats could dive beneath such layers to avoid detection. Modern nuclear and diesel submarines use this tactic to this day.

ASDIC in a passive role
The device could also be used to listen as well as pinging. The propeller noises of the U-boat would sometimes be heard as well as its operation of various machinery and its use of compressed air in the ballast tanks to change depths. This was not very usual as one of the standard German tactics, when located, was to dive deep, rig for silent running and hide beneath a thermal layer at speeds slow enough to eliminate any cavitation from the propellers.

The attack
When the U-boat was located the attacking vessel would rush directly towards contact, usually at the speed of 15 knots. This run was used to determine the final movements of the target and further plot the final attack. The attacking vessel had to very sure where the boat was and estimate where it would be when the depth charges (or Hedgehogs) would reach its depth. Thus the attacking vessel would have to take a lead on the U-boat much as a hunter does on a bird. At 500 yards the allied commander hoped to know what the U-boat was doing and then he finalized his attack.

As the range closed the U-boat would pass under the beam of the ASDIC and be lost to the escort. The deeper the U-boat was the longer the range of the lost contact and thus more difficult to attack accurately. Normally a good and firm contact was lost at 300 yards. This did not affect the forward-throwing Hedgehogs as much as the depth charges.

Even if the attack was delivered with the correct lead angle and firing time there was no guarantee of damage to the U-boat since its depth could differ from the settings at which the depth charges were set to explode. The correct depth of the U-boat could only be guessed or estimated based on the range at which contact was lost.

U-boat's evasive maneuvers
The U-boats of course used tactics to evade the depth charges and Hedgehogs. The best time to act was when the attacking vessel had taken its lead angle and the ASDIC contact was just lost.

A very common German move was to run away from the escort and force it on a stern chase pinging through the wake of the U-boat which could give the ASDIC a hard time. Then at the moment of the ASDIC [losing] contact the U-boat took a radical turn to left or right and more often than nor escaped out of the attacking pattern.

Another one was to turn radically with great power and disturb the water in order to confuse the ASDIC sometimes causing the attacker to be shaken off. The Germans also often released chemical pellets, which would produce clouds of bubbles to reflect the sound waves of the ASDIC.

Yet another tactic was to dive very deep and under a thermal layer or beneath the depth at which depth charges were normally set to explode. From 1942 onwards depths of 200 meters (600 feet) were not uncommon in an evasive tactic.

Although it is often claimed that the name ASDIC is derived from "Anti-submarine Detection Investigation Committee", there is no trace of such a committee in the Admiralty's archives (see Willem Hackmann, Seek & Strike: Sonar, anti-submarine warfare and the Royal Navy 1914-54 (HMSO, London, 1984) xxv). Hackmann explains that the name almost certainly relates to the "Anti-submarine Division or Anti-submarine Division-ics" - the department that initiated the research into underwater detection in World War One.

[BigWalleye]

Thanks for the explanation, Zosimus.

[Sailor Steve]

ASDIC / Sonar
Thank you for the link. I would ask that when you copy and paste something like this that you use quote brackets so everyone can see that the words are someone else's and not yours. Also please do not quote more than the opening paragraph. This has led to legal difficulties in the past.

[UKönig]

Sorry gang, magnetic anomaly detection is another piece of equipment on its own. With all the u-boat books (factual and otherwise) I've been reading lately, it's not surprising that I'm mashing things together.
MAD is/was a valid system, but was exclusive to sonar. I beg everyone's pardon.

Here's some more info on MAD...

Magnetic anomaly detectors employed to detect submarines during World War II harnessed the fluxgate magnetometer, an inexpensive and easy to use technology developed in the 1930s by Victor Vacquier of Gulf Oil for finding ore deposits. MAD gear was used by both Japanese and U.S. anti-submarine forces, either towed by ship or mounted in aircraft to detect shallow submerged enemy submarines. The Japanese called the technology jikitanchiki (磁気探知機, "Magnetic Detector"). After the war, the U.S. Navy continued to develop MAD gear as a parallel development with sonar detection technologies.
There is some misunderstanding of the mechanism of detection of submarines in water using the MAD boom system. Magnetic moment displacement is ostensibly the main disturbance, yet submarines are detectable even when oriented parallel to the Earth's magnetic field, despite construction with non-ferromagnetic hulls. For example, the Soviet-Russian Alfa class submarine, whose hull is constructed out of titanium to give dramatic submerged performance and protection from detection by MAD sensors, is still detectable.
This is due in part to the fact that even submarines with titanium hull will still have a substantial content of ferromagnetic materials as the nuclear reactor, steam turbines, auxiliary diesel engines and numerous other systems will be manufactured from steel and nickel alloys.
First used in World War II, MAD uses the Earth's magnetosphere as a standard, detecting anomalies caused by large metallic vessels, such as submarines. Modern MAD arrays are usually contained in a long tail boom (fixed-wing aircraft) or an aerodynamic housing carried on a deployable tow line (helicopters). Keeping the sensor away from the plane's engines and avionics helps eliminate interference from the carrying platform.

At one time, reliance was placed on electronic warfare detection devices exploiting the submarine's need to perform radar sweeps and transmit responses to radio messages from home port. As frequency surveillance and direction finding became more sophisticated, these devices enjoyed some success. However, submariners soon learned not to rely on such transmitters in dangerous waters. Home bases can then use extremely low frequency radio signals, able to penetrate the ocean's surface, to reach submarines wherever they might be.

Again I apologize for that error, I was tired... :oops: