Can an iPhone placed inside a water tank receive wireless LAN signals?

[EleSuki]

I've been considering some questions related to the properties of silicon carbide used in stealth fighter jets, which is known for its ability to absorb electromagnetic waves. Firstly, I would like to know if it is possible to have a sealed iPhone inside a 60cm water tank (using a Ziplock bag, for example) and still be able to communicate with it via wireless LAN. Additionally, if a room were filled with silicon carbide chaff, similar to a tornado in a SANS room, would it prevent wireless LAN signals from being received even outside the water tank? I'm interested in understanding what would happen from a physics perspective.

 

[Baluncore]

Antennas are designed to operate in air, matched to free space, not to the high dielectric constant of water. It is probable that the iPhone would not receive underwater, as the high signal strength loss would prevent synchronisation with the network. An iPhone transmitter may refuse to transmit due to the high reflected energy from the mismatched antenna impedance.

What is a SANS room ?

 

[EleSuki]

Antennas are designed to operate in air, matched to free space, not to the high dielectric constant of water. It is probable that the iPhone would not receive underwater, as the high signal strength loss would prevent synchronisation with the network. An iPhone transmitter may refuse to transmit due to the high reflected energy from the mismatched antenna impedance.

What is a SANS room ?

Thank you very much. While the propagation of radio waves in the air is reliable, high-frequency electromagnetic waves such as those used in Wi-Fi can attenuate inside a water tank. It would be difficult to locate an iPhone submerged from a boat, it seems.

SANS, the character from the indie game made by overseas game developers, is a skeletal scientist monster who prefers jokes about being a monster born from bones. (SANS likes such joke)It's become a famous title, but that was a somewhat unrelated topic, sorry.

Now, regarding the electromagnetic wave absorption of silicon carbide, if, for example, there were enough silicon carbide powder present in a small tornado circulating around the same spot in a room, similar to the animated GIF, would the strength of the Wi-Fi signals in that room decrease?

Alternatively, even if silicon carbide chaff is constantly installed in the room, since it is only a part of the room, would it have no effect on the strength of the Wi-Fi signals? Considering the phenomenon of wave scattering, it doesn't seem to be related to the signal strength...

 

[Baluncore]

While the propagation of radio waves in the air is reliable, high-frequency electromagnetic waves such as those used in Wi-Fi can attenuate inside a water tank. It would be difficult to locate an iPhone submerged from a boat, it seems.

While water attenuates the signal more than air, it is more the step change in dielectric constant at the antenna-water-air boundaries, that makes water difficult. There is also a problem with determining direction in the presence of refraction at the boundary. That refraction makes it possible to "see" underwater transmitters better, since signals approaching the surface steeply from below, are bent to travel along the surface in the air, rather than to radiate up into space.

Now, regarding the electromagnetic wave absorption of silicon carbide, if, for example, there were enough silicon carbide powder present in a small tornado circulating around the same spot in a room, similar to the animated GIF, would the strength of the Wi-Fi signals in that room decrease?

Yes, it would decrease, but only slightly. Phone signals passing through the tornado would be attenuated, but since the volume of the tornado is small compared with the volume of the room, you would probably not notice the difference.

Alternatively, even if silicon carbide chaff is constantly installed in the room, since it is only a part of the room, would it have no effect on the strength of the Wi-Fi signals? Considering the phenomenon of wave scattering, it doesn't seem to be related to the signal strength...

There are many different paths taken by phone signals. The phone signal is spread spectrum, modulated by a digital sequence, so only the strongest signal is locked, and is decoded, all the other path lengths are ignored because the digital signal is out of time, delayed by the longer path.

Spread spectrum was originally developed by the military to prevent jamming of their signals. It works well for mobile phones and data links. Having fluttering aluminium foil tassels, attached to a fan, will not destroy the quality of a mobile phone signal.

 

[EleSuki]

Thank you for the detailed explanation. So, it seems that even rotating a small tornado with silicon carbide chaff in a corner of the room would only cause some degree of attenuation.

Now, if we were to design it, how could we potentially achieve a reduction of 1/2, 1/4, 1/8, or even eliminate the need for antennas altogether in a Wi-Fi signal?

For example, placing tornadoes in the four corners of the room, at the entrance, or allowing them to hover near the ceiling (if you could consider it as a thought experiment)..."

 

[Baluncore]

Now, if we were to design it, how could we potentially achieve a reduction of 1/2, 1/4, 1/8, or even eliminate the need for antennas altogether in a Wi-Fi signal?

The size of an efficient antenna is related to the wavelength. Raising the frequency, to shorter wavelength bands, will reduce antenna size.

Most mobile phones do not need inconvenient external antennas. Likewise, the antennas used for Wi-Fi now can be entirely inside the box, but people want to buy "wireless things" with a visible antenna.

For example, placing tornadoes in the four corners of the room, at the entrance, or allowing them to hover near the ceiling (if you could consider it as a thought experiment)..."

What is it with tornados of SiC ? Hanging a 377 ohm "space cloth" curtain would absorb more RF energy than a rotating cloud of SiC.
https://en.wikipedia.org/wiki/Space_cloth

If you want to stop Wi-Fi you will need to enclose the volume with a double-walled conductive sheet, having no hole diameter, or slot length, greater than about 1 cm.

 

[EleSuki]

Thank you, I was thinking of putting silicon carbide powder in a water tank and circulating the water in the tank so that the silicon carbide always stays in the cube, but the reply I received says that even a small tornado of silicon carbide does not attenuate the electromagnetic waves that much, so the effect is limited. I think the effect is limited.

I am glad to know that wireless LAN radio waves will continue to survive as long as we don't build a room that can be sealed with water or metal. Thank you very much!