ELi5: why mobile phone antena is cocncealed and represented as lines in motherboard board while mobile tower antena installed at hight?
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Phones, going into pockets, need compact and durable designs. They can’t reach three hundred feet into the air.
This really limits their ability to communicate. Fortunately cell towers do not need to fit into anybody’s pocket, so they can be huge. This also helps to make up for the less than ideal size and shape of the cellular antenna.
Physics and requirements.
A mobile phone has the requirement to be, well, mobile. As such there’s not a lot of space for large antennae. If you look back at the earlier mobiles they had (extendable) external antennae (eg. the [Nokia 3110](https://en.wikipedia.org/wiki/Nokia_3110)). But if you want to be mobile you also can’t use a directional antenna since these have to be pretty finely aligned. Now combine the small form factor with an omnidirectional antenna and you get very low transmission and reception power.
On the mobile towers you don’t have that issue. On those you can install big antennae that can capture very tiny signals from all the noise around it (and modern setups can even do tunable directionality through [MIMO](https://en.wikipedia.org/wiki/MIMO) configuration, improving on that even more) _and_ you can push a lot more power into those for transmission.
Mobile phone antennas are NOT concealed and represented as lines in the board, quite the contrary, the antennas are very visible, it’s just built as the frame of the phone.
You are holding the antennas all the time without realizing it.
Because cell phone transmission are from phone to cell station and not from phone to phone. Since all phones need to talk to the cell station (and cell is more or less line of sight), it is imperative that the cell stations be accessible to the largest number of customers as possible, so they are placed high up on towers. It really doesn’t matter if you have a line of sight to other cell phones or not because any communication done to them is through the cell station.
Antennas typically operate best (most efficiently) with a size equal to about half their wavelength. The wavelength of cell phones is somewhere around 6 to 12 inches depending upon the particular frequency. This is too large for your cell phone, so they trade efficiency for size. For the cell station, they have plenty of room, so will go with the most efficient size.
Mobile phones have tight size requirements so their antennas have to be well designed to fit into a small form factor. Large broadcasting antennas do not have the same contraints. But generally two antennas that transmit at the same frequencies are of similar sizes.