Radio is part of the EM spectrum. EM waves (including light) decay under water at an exponential rate due to absorption by the medium. So data transmission underwater must rely instead on mechanical waves (sound).
This is why underwater robots mostly use tethers, otherwise you couldn't control them very well (RC control would stop working at a very shallow depth).
Note: why are folks downvoting an honest question?
I remember being told in some physics class that visible light is actually the radiation which penetrates the most, and that indeed this may be the very reason why it's visible: eyes were developed when life was still aquatic, therefore they evolved to be sensitive to the range of frequencies that could reach them.
Most water you’d drop a phone into has enough traces of salt to make it conductive. Therefore, the water acts like a faraday cage.
Theres a calculation you can do to calculate this, its pretty standard E&M stuff. Basically you calculate the skin depth of the material and thats as far as the signal can penetrate. The derivation highlights some cool things:
1. Its frequency dependent. This is why military submarines communicate at around 30 Hz.
2. Your audio cable (and all high frequency power cables) are stranded
3. Your microwave is effectively shielded with a thin layer of metal
4. An induction stove wont work with Al pans, but will quickly melt Al foil
Lots of answers already, but let me contribute this little heuristic:
Radio waves, being EM radiation, are just light - like "visible light", except our eyes can't see it. There are some peculiarities related to wavelengths (particularly when they get very large, or close to the size of a regular surface pattern of an illuminated object), but to a good approximation, you can mentally replace "radio antenna" with "a lightbulb", and make correct determinations about how radio behaves.
In this case: much like you can't see much in water, compared to air, and a submerged flashlight also doesn't shine very far, a submerged phone has a hard time seeing signals, and its emissions don't travel far either.
That's a good question, submarines use very low frequencies for communication, so I assume bluetooth/GSM might be pretty attenuated by the water? But also it might have turned off due to the water shorting something?
4G and 5G are going to depend on the mobile carrier. In the US, at least, that's usually going to be somewhere between 850MHz and 2100MHz. I recall reading something more recent about 700MHz being opened up in some areas.
Looks like Germany is 700-2600MHz for 4G, with 5G up at 3500MHz[0].
For underwater stuff it looks like you need something much lower in the kHz range[1], at least for distances of up to a couple hundred feet. Obviously this particular situation involves a much shorter distance. The page on MF radio[2] does mention water, and talks about frequencies up to 3MHz, but that's still way lower than any LTE bands used.
the same general reason why microwave band radio sees signal fade when there's rain on a point-to-point link through the air, but magnified greatly since the radio is now inside a solid mass of water. One of the problems faced by modern submarines for data communications, they use either ELF/VLF trailing antennas that are spooled out, while running 'kind of' shallow, or buoys, or antennas on periscope masts.
kajecounterhack|4 years ago
This is why underwater robots mostly use tethers, otherwise you couldn't control them very well (RC control would stop working at a very shallow depth).
Note: why are folks downvoting an honest question?
marche|4 years ago
I remember being told in some physics class that visible light is actually the radiation which penetrates the most, and that indeed this may be the very reason why it's visible: eyes were developed when life was still aquatic, therefore they evolved to be sensitive to the range of frequencies that could reach them.
potatoman22|4 years ago
hutzlibu|4 years ago
I suppose because of Friday.
em_rocks|4 years ago
Theres a calculation you can do to calculate this, its pretty standard E&M stuff. Basically you calculate the skin depth of the material and thats as far as the signal can penetrate. The derivation highlights some cool things:
1. Its frequency dependent. This is why military submarines communicate at around 30 Hz.
2. Your audio cable (and all high frequency power cables) are stranded
3. Your microwave is effectively shielded with a thin layer of metal
4. An induction stove wont work with Al pans, but will quickly melt Al foil
frosted-flakes|4 years ago
TeMPOraL|4 years ago
Radio waves, being EM radiation, are just light - like "visible light", except our eyes can't see it. There are some peculiarities related to wavelengths (particularly when they get very large, or close to the size of a regular surface pattern of an illuminated object), but to a good approximation, you can mentally replace "radio antenna" with "a lightbulb", and make correct determinations about how radio behaves.
In this case: much like you can't see much in water, compared to air, and a submerged flashlight also doesn't shine very far, a submerged phone has a hard time seeing signals, and its emissions don't travel far either.
anfractuosity|4 years ago
kajecounterhack|4 years ago
naikrovek|4 years ago
so that's Bluetooth and wi-fi ruled out.
GPS is a lower frequency, ~1.5GHz I think, and GPS is already an extremely low power signal.
I don't know about 4g or 5g though.
kelnos|4 years ago
Looks like Germany is 700-2600MHz for 4G, with 5G up at 3500MHz[0].
For underwater stuff it looks like you need something much lower in the kHz range[1], at least for distances of up to a couple hundred feet. Obviously this particular situation involves a much shorter distance. The page on MF radio[2] does mention water, and talks about frequencies up to 3MHz, but that's still way lower than any LTE bands used.
[0] https://www.gsmarena.com/network-bands.php3?sCountry=GERMANY
[1] https://en.wikipedia.org/wiki/Communication_with_submarines
[2] https://en.wikipedia.org/wiki/Medium_frequency
moepstar|4 years ago
I once tested that with a waterproof phone in clear water, can't recall which phone it was tho...
Don't feel brave enough to try it with my iPhone 8, even tho it supposedly is waterproof as well - my SO once tested it with a spilled drink...
walrus01|4 years ago
the same general reason why microwave band radio sees signal fade when there's rain on a point-to-point link through the air, but magnified greatly since the radio is now inside a solid mass of water. One of the problems faced by modern submarines for data communications, they use either ELF/VLF trailing antennas that are spooled out, while running 'kind of' shallow, or buoys, or antennas on periscope masts.
Sharlin|4 years ago
js2|4 years ago
unknown|4 years ago
[deleted]
zamadatix|4 years ago
detaro|4 years ago
kazinator|4 years ago