Power Output from mast / cellphone

[Dolby]

Someone is suggesting that a cellphone (device) and a cell tower, put out the same amount of power ... his thinking is that communication is two way, so it needs to be that way..

Does anyone know what power each transmits, to show him he's incorrect ?
I'm sure the device was a faction of a tower?

 

[gfmalan]

This is not an easy answer as there are many factors (amount of antennas, height above ground, urban or non urban area, technology type, etc.).

The FCC limit the max power 500 watt (ERP) per channel, but in urban areas it get adjusted to what is needed, typically in the 80-120 watt ERP range.

To compare apples with apples, 100 watt ERP is roughly 6-10 watt of raidiated power.

The mobile phones use to have 2 options, 0.6 watt or 3 watt, the brick size phones even had 5watt.

Transmission power is variable.

For your argument, a phone = 3 watt, average cell site/tower = 100 watt.

You can tell your friend, yes he is sortoff correct, the cell site give 5-10 watt per channel and the phone up to 3 without a extra antenna, but the cell site isn’t only serving his device, so much more combined power when you take all the channels available.

 

[sajunky]

FCC limits were created before sector antennas were introduced to the cellphone industry, there are obsolete. With 5G on the agenda there are calls to revise FCC limits. More bands increase total exposure and must be also taken into account. Also a common practice is to rent tower antennas to other networks adding more sector antennas, each one regulated separately, but not by a total amount.

There is no easy way to correlate ERP with maximum transmission power. Sector antennas dynamically tune radiation power according to a quality reported by the client and create beam forming that gives specific direction of a microwave beam for the particular user. It means that we cannot talk straight about ERP (or EIRP) of the antenna, as spatial radiation is changing all the time.

This radiation amount is multiplied by number of users. If number of users are located in the same direction, they will receive proportionally more radiation, probably much exceeding FCC limits. I strongly suspect that on-board computers do not calculate such extreme cases, it let it put wild. It is why I wrote these limits are obsolete.

With only one user, transmition power is very small (only few times of the cellphone, as I have been told), plus a constant full power radiation in control channels. It increases by a factor of number serving users.